CPG Nation Forum - COMP Cams Product Tech http://www.cpgnation.com/forum en Sun, 01 Aug 2010 08:28:38 GMT vBulletin 1 http://www.cpgnation.com/forum/images/ca_serenity_red/misc/rss.jpg CPG Nation Forum - COMP Cams Product Tech http://www.cpgnation.com/forum Matters of Control – Stud Mount vs. Shaft Mount Rocker Arms http://www.cpgnation.com/forum/matters-control-stud-mount-vs-shaft-3860-new-post.html Tue, 22 Jun 2010 15:21:58 GMT COMP Cams takes an in-depth look at two easy ways to improve valve train durability and raise your redline at the same time

Engines, by nature, are a bundle of compromises. Durability versus weight. Fuel economy versus power. You get the idea. It all comes down to making decisions on what you want versus what you’re willing to give up.

And nowhere are those decisions tougher than when it comes to the valve train. Or at least that’s what we’ve always been told. Engineers at COMP Cams have been working to eliminate weaknesses without giving up anything in return and have found ways to simply eliminate many of the compromises that engine builders are normally forced to make.

They can do this because COMP is involved in the valve train from the camshaft all the way through the valves. This includes everything from retainers to locks to valve springs to lifters and even lubricants to keep everything moving smoothly. And one area where they have found engine builders and horsepower freaks can greatly improve their engines’ valve trains without giving anything up in return is creating a stable platform for the rocker arms to do their job.

When it comes to pushrod engines, the most popular design for locating the rocker arms is the pedestal-mount rocker stud. On the low-end (think OEMs), they are 3/8-inch diameter rocker studs pressed into the cylinder head. The OEMs liked this system because it was cheap to produce, but in performance applications, raising the valve spring pressure can pull the studs right out of the heads.

[IMGLFT=Stud mount rockers]http://www.cpgnation.com/filehost/files/6/COMP Images/StudvsShaftRockers/1601%20%28640%29.jpg[/IMGLFT]The next step up is a screw-in rocker stud. These are commonly available in either 3/8-inch or a larger 7/16-inch size diameter. Screw-in studs can handle much greater spring pressures, and while the larger, 7/16-inch diameter studs do add stiffness, the final result is probably not as much as you might think.

"Rocker stud flex doesn’t just take place in the upper RPM range,” explains engine builder Keith Dorton of Automotive Specialists, whose race engines regularly dominate in the USAR Pro Cup Series. “You can see it by doing a simple test. Pull the valve cover off your engine and place a dial indicator laterally on the end of the rocker stud, or the adjuster nut if necessary, on the opposite end of the valve stem. Then turn the crankshaft over by hand and watch to see how much movement you get on the dial indicator. If you aren’t using a stud girdle you will see some movement on practically every engine, and on some engines it will scare you to death.”









At first glance it isn’t obvious why a rocker stud will flex even when turning an engine’s rotating assembly by hand. After all, its only purpose is to provide a pivot point for the rocker arm, right?

Ideally, that is correct, but there’s a lot more going on in the real world. On almost all pushrod engines, the rocker stud is on an angle to the valve stem. More specifically, the many angles involved in getting a valve train to work as efficiently as possible force the top of the rocker stud and the top of the valve stem to be angled toward each other. So when the camshaft tries to open the valve, the spring pushes back through the rocker arm and causes the rocker stud to flex back, away from the spring.

When the rocker stud flexes, lots of things happen, and none of them are good. First, it puts unintended motion into the valve train. The rocker arm moves off the center of the valve stem tip and can cause early wear of the valve, the rocker tip and even the valve guide. There’s no telling how many engine builders have blamed a broken valve on the manufacturer or a too-aggressive camshaft when the real culprit was the rocker stud. Flex in the rocker stud can also break the rocker stud boss on the cylinder head.

A second effect—which may be even more important to racers—is that the flex in the rocker stud causes the valves to stay closed just a fraction of a second longer and not reach maximum valve lift. The effect is to take the cam that you spent so much effort finding the perfect specs for and make it act smaller. Everything from total duration to overlap changes can significantly reduce the amount of air and fuel you are getting into the combustion chambers.

Interestingly, Dorton says that the cylinder heads most prone to allow flex are the same ones most likely to be used by racers and performance enthusiasts. Aluminum cylinder heads are lighter than cast iron, but the material is also softer. Likewise, heads designed for performance usually also have any extra material carved away to shave off even more weight. But this also means the rocker stud bosses rarely have any more material than necessary. It’s not a design flaw—after all, reducing weight is important—but it does mean a smart engine builder should be aware of it.

[IMGLFT=Stud girdles]http://www.cpgnation.com/filehost/files/6/COMP Images/StudvsShaftRockers/4022%20%28640%29.jpg[/IMGLFT]Fortunately, there are two easy ways to increase the stability of the rocker arm. If you have already invested in a stud-mounted rocker system, a rocker stud girdle adds very little weight and ties all the rocker studs on a cylinder head together to greatly increase rigidity. A rocker stud girdle is essentially a large clamp that locks down on all of the adjuster nuts on top of the studs. Once it is in place, it takes the force of one valve spring trying to push back on a single rocker stud and transfers it to the entire network. Since the valves are actuated at different times, this is an efficient way to spread out the load without creating any extra stress on the overall valve train setup. It’s a relatively simple device and since it can be constructed from aluminum, it adds very little to the overall weight of any engine. The only changes required will be extended rocker adjusters (which are usually included in any girdle kit) and possibly taller valve covers.

“A girdle is practically always going to be beneficial versus not having one,” explains Sandy Wilkins, who manages the drag racing engine program for Roush Yates Engines. “Anything you can do to stabilize the rocker system is a good idea. But, at least in racing, any time you are going from a flat tappet camshaft to a roller cam, I’d consider at least a rocker girdle to be mandatory if it is allowed in the rules. And that’s because of the higher spring pressures you can run with a roller cam. On a flat tappet camshaft, you might max out with a spring that has 400 pounds of open pressure, but on a roller you can get away with as much as maybe 700 pounds of open pressure. That extra spring pressure will really stress those rocker studs so strengthening that area can only help. I’ve seen gains exceed 20 horsepower on some engines by getting rid of deflection around the rocker arms.”

[IMGRT=Shaft mount rocker system]http://www.cpgnation.com/filehost/files/6/COMP Images/StudvsShaftRockers/1501%20%28640%29.jpg[/IMGRT]A second solution for increasing the stability of the rocker arms is to swap out the rocker stud system for a shaft-mounted rocker system. Shaft-mount rockers, instead of bolting up individually on vertical rocker studs, pivot on horizontal shafts that are in turn bolted to stands which are securely mounted to the top of the cylinder head. This setup in much more stable than a traditional rocker stud system and virtually eliminates flex--which is why you will find shaft rockers in practically every engine in every top-level racing series.

As recently as a few years ago, shaft-mount rocker systems were expensive and tricky to set up on a new engine, which made them the domain of big-money race teams and high-end applications. But COMP has developed a line of sportsman level shaft rocker systems for many different applications that reduces the cost of adding a shaft rocker system to an engine without giving up any of the benefits. Most bolt directly to the cylinder head and include shims to help you get the correct valve train geometry for excellent valve control and maximum component life. Now, instead of a single 7/16-inch stud holding the rocker in place, you have a rocker pivoting on a shaft, which in turn is bolted to a substantial pedestal which leaves little opportunity for flex in any direction.

While researching this topic, we heard stories of engine builders adding a rocker stud girdle to their existing valve train or switching to a shaft-mount rocker system and being surprised to find horsepower drop. It turns out that it wasn’t a fault of the stiffer valve train, but over time the engine builder had constantly tested new camshaft grinds and wound up with a lobe design that compensated for the flex in the system. By going to a smaller camshaft, the engine not only regained the lost power—and then some—but it also eliminated the strain on the valve train from an over-aggressive camshaft, and the more stable system pushed the redline higher in the rpm range.

So which system is better for you? “It all depends,” is the answer Wilkins gave us.

“I would always promote using a shaft-mount system if you can,” he says, “but that’s not always possible. Maybe your rulebook won’t allow it or you have an oddball engine that nobody makes one for.

Then there’s also a financial consideration. If you already have your studs and rockers, then you will come out cheaper by investing in a good rocker stud girdle. But if you are building your engine from scratch, that’s a different story. When you consider that for a stud-mount system that you’ve got to buy the screw-in studs, guideplates, rocker arms, the stud girdle and the adjuster nuts to go along with it, that all adds up. In the end, you may be able to get away with only paying about a hundred bucks or so more for a good sportsman level shaft-mount rocker system. And once they are set up on your cylinder heads properly, they are pretty bulletproof.”

]]> COMP Cams takes an in-depth look at two easy ways to improve valve train durability and raise your redline at the same time



Engines, by nature, are a bundle of compromises. Durability versus weight. Fuel economy versus power. You get the idea. It all comes down to making decisions on what you want versus what you’re willing to give up.



And nowhere are those decisions tougher than when it comes to the valve train. Or at least that’s what we’ve always been told. Engineers at COMP Cams have been working to eliminate weaknesses without giving up anything in return and have found ways to simply eliminate many of the compromises that engine builders are normally forced to make.



They can do this because COMP is involved in the valve train from the camshaft all the way through the valves. This includes everything from retainers to locks to valve springs to lifters and even lubricants to keep everything moving smoothly. And one area where they have found engine builders and horsepower freaks can greatly improve their engines’ valve trains without giving anything up in return is creating a stable platform for the rocker arms to do their job.



When it comes to pushrod engines, the most popular design for locating the rocker arms is the pedestal-mount rocker stud. On the low-end (think OEMs), they are 3/8-inch diameter rocker studs pressed into the cylinder head. The OEMs liked this system because it was cheap to produce, but in performance applications, raising the valve spring pressure can pull the studs right out of the heads.



[IMGLFT=Stud mount rockers]http://www.cpgnation.com/filehost/files/6/COMP Images/StudvsShaftRockers/1601%20%28640%29.jpg[/IMGLFT]The next step up is a screw-in rocker stud. These are commonly available in either 3/8-inch or a larger 7/16-inch size diameter. Screw-in studs can handle much greater spring pressures, and while the larger, 7/16-inch diameter studs do add stiffness, the final result is probably not as much as you might think.



"Rocker stud flex doesn’t just take place in the upper RPM range,” explains engine builder Keith Dorton of Automotive Specialists, whose race engines regularly dominate in the USAR Pro Cup Series. “You can see it by doing a simple test. Pull the valve cover off your engine and place a dial indicator laterally on the end of the rocker stud, or the adjuster nut if necessary, on the opposite end of the valve stem. Then turn the crankshaft over by hand and watch to see how much movement you get on the dial indicator. If you aren’t using a stud girdle you will see some movement on practically every engine, and on some engines it will scare you to death.”



















At first glance it isn’t obvious why a rocker stud will flex even when turning an engine’s rotating assembly by hand. After all, its only purpose is to provide a pivot point for the rocker arm, right?



Ideally, that is correct, but there’s a lot more going on in the real world. On almost all pushrod engines, the rocker stud is on an angle to the valve stem. More specifically, the many angles involved in getting a valve train to work as efficiently as possible force the top of the rocker stud and the top of the valve stem to be angled toward each other. So when the camshaft tries to open the valve, the spring pushes back through the rocker arm and causes the rocker stud to flex back, away from the spring.



When the rocker stud flexes, lots of things happen, and none of them are good. First, it puts unintended motion into the valve train. The rocker arm moves off the center of the valve stem tip and can cause early wear of the valve, the rocker tip and even the valve guide. There’s no telling how many engine builders have blamed a broken valve on the manufacturer or a too-aggressive camshaft when the real culprit was the rocker stud. Flex in the rocker stud can also break the rocker stud boss on the cylinder head.



A second effect—which may be even more important to racers—is that the flex in the rocker stud causes the valves to stay closed just a fraction of a second longer and not reach maximum valve lift. The effect is to take the cam that you spent so much effort finding the perfect specs for and make it act smaller. Everything from total duration to overlap changes can significantly reduce the amount of air and fuel you are getting into the combustion chambers.



Interestingly, Dorton says that the cylinder heads most prone to allow flex are the same ones most likely to be used by racers and performance enthusiasts. Aluminum cylinder heads are lighter than cast iron, but the material is also softer. Likewise, heads designed for performance usually also have any extra material carved away to shave off even more weight. But this also means the rocker stud bosses rarely have any more material than necessary. It’s not a design flaw—after all, reducing weight is important—but it does mean a smart engine builder should be aware of it.



[IMGLFT=Stud girdles]http://www.cpgnation.com/filehost/files/6/COMP Images/StudvsShaftRockers/4022%20%28640%29.jpg[/IMGLFT]Fortunately, there are two easy ways to increase the stability of the rocker arm. If you have already invested in a stud-mounted rocker system, a rocker stud girdle adds very little weight and ties all the rocker studs on a cylinder head together to greatly increase rigidity. A rocker stud girdle is essentially a large clamp that locks down on all of the adjuster nuts on top of the studs. Once it is in place, it takes the force of one valve spring trying to push back on a single rocker stud and transfers it to the entire network. Since the valves are actuated at different times, this is an efficient way to spread out the load without creating any extra stress on the overall valve train setup. It’s a relatively simple device and since it can be constructed from aluminum, it adds very little to the overall weight of any engine. The only changes required will be extended rocker adjusters (which are usually included in any girdle kit) and possibly taller valve covers.



“A girdle is practically always going to be beneficial versus not having one,” explains Sandy Wilkins, who manages the drag racing engine program for Roush Yates Engines. “Anything you can do to stabilize the rocker system is a good idea. But, at least in racing, any time you are going from a flat tappet camshaft to a roller cam, I’d consider at least a rocker girdle to be mandatory if it is allowed in the rules. And that’s because of the higher spring pressures you can run with a roller cam. On a flat tappet camshaft, you might max out with a spring that has 400 pounds of open pressure, but on a roller you can get away with as much as maybe 700 pounds of open pressure. That extra spring pressure will really stress those rocker studs so strengthening that area can only help. I’ve seen gains exceed 20 horsepower on some engines by getting rid of deflection around the rocker arms.”



[IMGRT=Shaft mount rocker system]http://www.cpgnation.com/filehost/files/6/COMP Images/StudvsShaftRockers/1501%20%28640%29.jpg[/IMGRT]A second solution for increasing the stability of the rocker arms is to swap out the rocker stud system for a shaft-mounted rocker system. Shaft-mount rockers, instead of bolting up individually on vertical rocker studs, pivot on horizontal shafts that are in turn bolted to stands which are securely mounted to the top of the cylinder head. This setup in much more stable than a traditional rocker stud system and virtually eliminates flex--which is why you will find shaft rockers in practically every engine in every top-level racing series.



As recently as a few years ago, shaft-mount rocker systems were expensive and tricky to set up on a new engine, which made them the domain of big-money race teams and high-end applications. But COMP has developed a line of sportsman level shaft rocker systems for many different applications that reduces the cost of adding a shaft rocker system to an engine without giving up any of the benefits. Most bolt directly to the cylinder head and include shims to help you get the correct valve train geometry for excellent valve control and maximum component life. Now, instead of a single 7/16-inch stud holding the rocker in place, you have a rocker pivoting on a shaft, which in turn is bolted to a substantial pedestal which leaves little opportunity for flex in any direction.



While researching this topic, we heard stories of engine builders adding a rocker stud girdle to their existing valve train or switching to a shaft-mount rocker system and being surprised to find horsepower drop. It turns out that it wasn’t a fault of the stiffer valve train, but over time the engine builder had constantly tested new camshaft grinds and wound up with a lobe design that compensated for the flex in the system. By going to a smaller camshaft, the engine not only regained the lost power—and then some—but it also eliminated the strain on the valve train from an over-aggressive camshaft, and the more stable system pushed the redline higher in the rpm range.



So which system is better for you? “It all depends,” is the answer Wilkins gave us.



“I would always promote using a shaft-mount system if you can,” he says, “but that’s not always possible. Maybe your rulebook won’t allow it or you have an oddball engine that nobody makes one for.



Then there’s also a financial consideration. If you already have your studs and rockers, then you will come out cheaper by investing in a good rocker stud girdle. But if you are building your engine from scratch, that’s a different story. When you consider that for a stud-mount system that you’ve got to buy the screw-in studs, guideplates, rocker arms, the stud girdle and the adjuster nuts to go along with it, that all adds up. In the end, you may be able to get away with only paying about a hundred bucks or so more for a good sportsman level shaft-mount rocker system. And once they are set up on your cylinder heads properly, they are pretty bulletproof.”




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]]> COMP Cams Product Tech hanaylor http://www.cpgnation.com/forum/matters-control-stud-mount-vs-shaft-3860.html COMP Cams® Top 10 Tech FAQs http://www.cpgnation.com/forum/comp-cams-top-10-tech-faqs-3773-new-post.html Fri, 14 May 2010 19:08:10 GMT From measuring pushrods to degreeing camshafts, read on to find answers to the ten most frequently asked questions that COMP Cams® Technicians receive.

1. How do I set valves for hydraulic and solid lifters?

Adjusting intake valves:
We recommend you work with one cylinder at a time. Using the crankshaft dampener bolt in the snout of the crankshaft, turn the engine over by hand in the direction of its running rotation until the exhaust pushrod just begins to move upward to open the valve. Stop rotation. The intake lifter is now on the base circle of the cam, and the intake valve is ready to be adjusted.
Hydraulic Lifter Cams:
Tighten the polylock until all the slack is taken out of the rocker arm and pushrod. By lightly turning the pushrod with your fingers as you tighten the polylock, you will discover or feel a point at which there will be slight resistance. At this point, you have taken all the excess slack out of the pushrod. You are now at what we refer to as “zero lash.” Turn the polylock 1/2 turn more, and while holding it with a wrench, tighten the set screw using a T-handle or Allen wrench. This will give you the ideal preload of the rocker arm, pushrod and lifter. Repeat this procedure for each cylinder and carefully adjust all intake valves.
Solid Lifter Cams:
Consult cam spec card or cam manufacturer for correct lash specifications. With the proper feeler gauge between the roller and valve stem, turn the polylock until a slight drag is felt on the feeler gauge. Hold the polylock with the wrench, and then tighten the set screw using a T-handle or Allen wrench. Repeat this procedure for each cylinder and carefully adjust all intake valves.

Adjusting exhaust valve:
To adjust exhaust valves, turn the engine over until the intake pushrod moves all the way up. Rotate past maximum lift, approximately 1/2 to 2/3 of the way back down. The exhaust lifter is now on the base circle and the exhaust valve can be adjusted.
Hydraulic Lifter Cam:
Rotate the exhaust pushrod with your fingers and begin to
tighten the exhaust polylock. When you feel resistance on the pushrod, you are at “zero lash.” Rotate the polylock 1/2 turn more, and then tighten the set screw. Go through the exhaust valves, and repeat the procedure carefully. Now all of the valves are adjusted with the proper preload.
Solid lifter Cam:
Tighten the polylock, with the proper feeler gauge between the roller tip and valve, to the point at which there is a slight drag when moving the feeler gauge. Hold the polylock with the wrench and tighten set screw. Following this procedure, carefully adjust all exhaust valves.

2. How much preload should I look for in a typical hydraulic Lifter?

You should look for .030-.060 of preload.


3. How do you figure out what your lift will be with a different rocker ratio?

You take the lobe lift given on the card and multiply it by the rocker ratio (e.g.,.400 x 1.6 = .640). Or you can divide the valve lift given on the card by the rocker ratio it is given with, and then multiply it by the new rocker ratio.


4. What is the difference between different Lobe separations?

Tighter lobe separation tends to narrow the power band and typically increase the peaks. Tighter separation will also increase cylinder pressure and increase bottom end torque. Narrow also reduces piston to valve clearance, hence too narrow creates many issues with fitment. Also, narrow will decrease engine vacuum at idle and may cause issues with misfire. And, wider lobe separation will do the opposite of the points on tighter separation.

Lobe Separation = (Intake Centerline + Exhaust Centerline)/2


5. What is the difference between different Intake Centerlines and how is this not the same as lobe separation?

By advancing and retarding a cam, you can move the ICL wherever you would like, but unless you have separate cams for the intake and exhaust (like the DOHC Ford) you cannot change the lobe separation once a cam is ground. Advancing the cam will make more cylinder pressure and build bottom end while retarding will broaden the power band and add top end, but can also make the motor a little lazier on the bottom.


6. How do you determine pushrod length with a checking tool?

Technique #1
This technique requires the use of a COMP Cams® Hi-Tech™ Pushrod Length Checker. These are marked with a standard length stamped in them. This number represents the gauge length of the part (.140" gauge diameter), with the two halves screwed completely together. Extending the pushrod one rotation lengthens the gauge length .050". For example, a pushrod stamped 7.800 and screwed apart one rotation would be 7.800" + .050" = 7.850" gauge length. Therefore, you would order the part number from the catalog that matches this gauge length, since gauge length is how they are listed.
Technique #2
This technique requires one of our Magnum Pushrod Length Checkers. Once fixed, you don’t need to have an expensive gauge or a pair of calipers to measure it. You just need a pushrod of a known length to compare it to (a standard). Then use a pair of common 6" calipers to measure the difference between the standard and yours.
Here are a few final tips for pushrods in general. It is always a good idea to buy a few spares when purchasing a set of custom length pushrods, and stick them in your toolbox. If one ever fails at the track, and you need a replacement, it would be nearly impossible to borrow one from a fellow racer.

Another hint involves cup end pushrods. Measuring them for length is especially difficult, no matter which technique above you choose to use. The size and shape of the cup end varies greatly from manufacturer to manufacturer, so measuring from the ball end to the cup end over the cup surface is a dangerous practice. The best strategy is to drop a 5/16" diameter steel ball into the cup end, and do all measuring over this ball, subtracting the 5/16" diameter (.3125") to calculate the length.


7. How do you check piston to valve clearance?

Step 1:
With the camshaft installed, remove the cylinder head from the block. Clean the combustion chamber and the top of the piston and valve reliefs. The cleaner the piston, the better the clay will stick to it.

Step 2:

Apply a strip of model clay 3/8” to 1/2” wide and approximately 1/4” thick to the pistons. The clay strips should be placed perpendicular (across) to the intake and exhaust valve reliefs (fig. 1). Applying a small amount of oil to the clay will prevent it from sticking to the valves as they press into the clay.

Step 3:
Reinstall the cylinder head with the gasket that is going to be used. It will not be necessary to re-torque the head yet. All head gasket manufacturers can tell you what the compressed thickness of their gasket will be. Measure the gasket before you install it permanently, and add the difference of the gasket thickness to your piston to valve clearance. This will be within .001” or .002” of the exact clearance. Install a sufficient number of head bolts to secure the head in place while you are rotating the engine. Install the pushrods, lifters and rocker arms on the cylinder you have prepared for the clearance check.

Step 4:

Adjust the rocker arms to their suggested clearance. If the camshaft you are checking uses hydraulic lifters, you must temporarily use solid lifters in their place. Hydraulic lifters bleed down and would create a false measurement. Once the hydraulic lifters are replaced with solid lifters, adjust the lash to “zero.” Be sure not to pre-load the valve spring (fig. 2) (be sure to reinstall the hydraulic lifters before starting the engine).

Step 5:
Turn the engine over by hand in the normal direction of rotation. Be sure to rotate the engine over 2 times. This will be one complete revolution of the cam and, it will assure you of an accurate reading on both the intake and exhaust. Remove the cylinder head from the block. Be sure to do this gently, so the clay is not disturbed. It may be stuck to the valves or combustion chamber, so be careful.

Step 6:

With a razor or a sharp knife, slice the clay cleanly, lengthwise through the depression and peel half of it off the piston (fig. 3). The clay’s thickness in the thinnest area will represent the minimum piston to valve clearance.

Step 7:
To accurately check the thickness, use a set of dial calipers (fig. 4). The clay can also be measured close enough with a thin steel rule.

Note: Be sure to check piston to valve clearance after the cam has been degreed in. The positioning of the cam in the engine will greatly affect the piston to valve clearance.



8. How do I degree a camshaft, and why we do we use the Intake Centerline Method instead of valve timing events?

The Intake Centerline Method

There are several accepted ways to degree a camshaft. At COMP Cams®, we feel the Intake Centerline Method is the easiest and most accurate. This method of cam degreeing is very practical and indifferent to design characteristics. It simply involves positioning the center, or point of maximum lift, of the #1 intake lobe with Top Dead Center of the #1 piston.

The Intake Centerline Method still requires accuracy to be correct, but it is somewhat more forgiving. Once you have degreed a camshaft using this method, you will be surprised at its ease. We also recommend positioning the dial indicator on the #1 intake retainer because lift measurements will include any deflection that may occur in the pushrod and rocker arm. This makes the degreeing process as accurate as possible in relation to what actually goes on inside the engine. Before you proceed, you will need a Cam Degree Kit (Part #4796) from COMP Cams®.


Time to Go to Work

Step 1:
The camshaft and timing set have been installed. Make sure that the timing marks on both the cam gear and crank gear are aligned properly, per the cam installation instructions. Use chalk or similar marker to better define the marks.

Step 2:
For example, we have our cam card, and it suggests we install the cam on 106 degree intake centerline. Install all the rocker arms and pushrods in the engine as normal. On the #1 intake lobe, install the solid lifter in place of the hydraulic lifter. If a solid lifter or roller cam is being checked, use that respective lifter. Adjust the #1 intake lash to exactly zero. Do not pre-load the lifter. Next, adjust the #1 exhaust lash to zero. You should be able to turn both pushrods with your fingers easily.

Step 3:
Attach your COMP Cams® pointer (Part #4794) to the block. Many people will make a pointer out of some sort of rigid, yet manageable wire. A stiff coat hanger wire works well.

Step 4:
Attach the degree wheel to the balancer, and install the assembly on the crankshaft
  • There are several ways to attach the degree wheel to the crankshaft. In our example, the degree wheel is mounted to the balancer. The crank may be rotated from either the front or from the flywheel end. Obviously, if the engine is in the car, you must rotate from the front.
  • Remember, the greater the leverage, the smoother the crank rotation, thus more accuracy. NEVER use the starter to turn the engine while degreeing the cam.

Step 5:
Before installing the piston stop, rotate the crankshaft to get the #1 piston in approximate T.D.C. position, with both the intake and exhaust valves closed. This can be a rough guess, but it can save you from making a mistake later. Adjust your pointer to zero or T.D.C. on the degree wheel.

Step 6:
Turn the crankshaft opposite the engine rotation approximately 15-20 degrees. This will lower the position enough to allow the T.D.C. stop to be installed in the spark plug hole. Screw in the piston stop until it touches the piston. (fig. A). Continue to turn the engine in the same direction until the piston comes back up and touches the piston stop. Mark the degree wheel with a pen or pencil on the number the pointer is on (fig. B). Turn the engine in the other direction (same as engine rotation) until the piston comes back up and touches the piston stop. Make a mark on the number the pointer is on (fig. C).

Step 7:
Remove the piston stop after marking the two points on your degree wheel. Rotate the crankshaft to the midpoint of the two marks. This point is T.D.C. for cylinder #1. Without rotating the crankshaft, adjust the degree wheel to read 0 degrees at the pointer (fig. D). You are now ready to locate the intake lobe centerline relative to T.D.C. If you are not absolutely sure that your 0 degree mark is set at T.D.C., repeat this procedure. This step is critical to proper cam alignment.

Step 8:
Attach the dial indicator to the dial indicator mount. Position the dial indicator mount so the tip will contact the retainer of the #1 intake valve (fig. E). It is important that the indicator plunger be parallel to the valve stem. Any variance in the angle of the indicator will introduce geometric errors into the lift readings.

Step 9:
Rotate the engine, in the normal direction of crankshaft rotation, until you reach maximum lift. The dial indicator will change direction at the point of maximum lift. At this point, set the dial to zero (fig. F).

Step 10:
Back the engine up (usually counter-clockwise) until the indicator reads .100”. Turn the engine back in the normal direction of rotation until (usually clockwise) the dial indicator reads .050” before maximum lift. Record the degree wheel reading.

Step 11:
Continue to rotate the engine over in its normal direction of rotation until the indicator goes past zero to .050” on the closing side of maximum lift. Again, record the degree wheel reading.

Step 12:
Add the two numbers together and divide by 2. That number will be the location of maximum lift of the intake lobe in relation to the crank and piston. This is the intake centerline. For example: The first degree wheel reading was 96 degrees. The second reading was 116 degrees. These two numbers (96 +116) added together will be 212. Dividing 212 by 2 will equal 106. Your actual intake centerline is 106 degrees. Reference back to your cam spec card, and we see that the recommended intake centerline for your camshaft is 106 degrees. Everything is where it should be. In the event that your camshaft did not degree in as per manufacturer’s specs, it will be necessary to either advance (move ahead) or retard (move back) the cam to meet suggested intake centerline. Depending on the engine application, there are several different suggested methods for advancing or retarding the camshaft. One common method is by use of a crank gear with multiple keyways, each one being at a slightly different relationship to the gear teeth. A second method is to use off-set bushings that fit on the cam pin and in the cam gear. The off-set will advance or retard the cam depending on how the bushing is placed on the cam pin. Another method is by off-set keys that fit into the crank gear keyway. A more elaborate system uses an adjustable timing gear. Contact COMP Cams® or your local COMP Cams® dealer for the method best suited to your application.

Note: When degreeing a cam, remember to look at the degree wheel as a full 360 degrees, no matter how the degree wheel you’re using is marked. Many degree wheels are marked in 90 degree or 180 degree increments. On wheels that are marked in 90 degree increments, keep in mind that you must continue to count the number of degrees past 90 degrees. Be sure all readings are taken from Top Dead Center. Keep in mind that to advance the cam, you must lower the intake centerline. For example, if our cam has a lobe separation of 110 degrees, the cam is “straight up” when the intake centerline is 110 degrees. Moving the centerline to 106 degrees advances the can 4 degrees. If we change the centerline to 112 degrees, this would be 2 degrees retarded.


9. What is installed height on a head and how does it affect the spring pressure and lift ability?

Basically, it is the height from the bottom of the retainer to the base of the head where the spring sets. Springs have recommended installed heights, and shorting or raising that height will affect the given specs for the spring. Shorting it will add pressure and take away lift ability; raising does just the opposite.


10. How do you properly break in a camshaft and what oils and additives should you use?

Use high zinc oil (such as the COMP Cams® Break-In Oil) with our 159 additive. Vary the RPM of the motor between 2000-2500 RPM for about 25 minutes. Do NOT try to constantly start the motor if you can not get it to fire with a new cam in it. ]]> From measuring pushrods to degreeing camshafts, read on to find answers to the ten most frequently asked questions that COMP Cams® Technicians receive.



1. How do I set valves for hydraulic and solid lifters?



Adjusting intake valves:
We recommend you work with one cylinder at a time. Using the crankshaft dampener bolt in the snout of the crankshaft, turn the engine over by hand in the direction of its running rotation until the exhaust pushrod just begins to move upward to open the valve. Stop rotation. The intake lifter is now on the base circle of the cam, and the intake valve is ready to be adjusted.
Hydraulic Lifter Cams:
Tighten the polylock until all the slack is taken out of the rocker arm and pushrod. By lightly turning the pushrod with your fingers as you tighten the polylock, you will discover or feel a point at which there will be slight resistance. At this point, you have taken all the excess slack out of the pushrod. You are now at what we refer to as “zero lash.” Turn the polylock 1/2 turn more, and while holding it with a wrench, tighten the set screw using a T-handle or Allen wrench. This will give you the ideal preload of the rocker arm, pushrod and lifter. Repeat this procedure for each cylinder and carefully adjust all intake valves.
Solid Lifter Cams:
Consult cam spec card or cam manufacturer for correct lash specifications. With the proper feeler gauge between the roller and valve stem, turn the polylock until a slight drag is felt on the feeler gauge. Hold the polylock with the wrench, and then tighten the set screw using a T-handle or Allen wrench. Repeat this procedure for each cylinder and carefully adjust all intake valves.


Adjusting exhaust valve:
To adjust exhaust valves, turn the engine over until the intake pushrod moves all the way up. Rotate past maximum lift, approximately 1/2 to 2/3 of the way back down. The exhaust lifter is now on the base circle and the exhaust valve can be adjusted.
Hydraulic Lifter Cam:
Rotate the exhaust pushrod with your fingers and begin to

tighten the exhaust polylock. When you feel resistance on the pushrod, you are at “zero lash.” Rotate the polylock 1/2 turn more, and then tighten the set screw. Go through the exhaust valves, and repeat the procedure carefully. Now all of the valves are adjusted with the proper preload.
Solid lifter Cam:
Tighten the polylock, with the proper feeler gauge between the roller tip and valve, to the point at which there is a slight drag when moving the feeler gauge. Hold the polylock with the wrench and tighten set screw. Following this procedure, carefully adjust all exhaust valves.


2. How much preload should I look for in a typical hydraulic Lifter?



You should look for .030-.060 of preload.





3. How do you figure out what your lift will be with a different rocker ratio?



You take the lobe lift given on the card and multiply it by the rocker ratio (e.g.,.400 x 1.6 = .640). Or you can divide the valve lift given on the card by the rocker ratio it is given with, and then multiply it by the new rocker ratio.





4. What is the difference between different Lobe separations?



Tighter lobe separation tends to narrow the power band and typically increase the peaks. Tighter separation will also increase cylinder pressure and increase bottom end torque. Narrow also reduces piston to valve clearance, hence too narrow creates many issues with fitment. Also, narrow will decrease engine vacuum at idle and may cause issues with misfire. And, wider lobe separation will do the opposite of the points on tighter separation.



Lobe Separation = (Intake Centerline + Exhaust Centerline)/2





5. What is the difference between different Intake Centerlines and how is this not the same as lobe separation?



By advancing and retarding a cam, you can move the ICL wherever you would like, but unless you have separate cams for the intake and exhaust (like the DOHC Ford) you cannot change the lobe separation once a cam is ground. Advancing the cam will make more cylinder pressure and build bottom end while retarding will broaden the power band and add top end, but can also make the motor a little lazier on the bottom.





6. How do you determine pushrod length with a checking tool?



Technique #1
This technique requires the use of a COMP Cams® Hi-Tech™ Pushrod Length Checker. These are marked with a standard length stamped in them. This number represents the gauge length of the part (.140" gauge diameter), with the two halves screwed completely together. Extending the pushrod one rotation lengthens the gauge length .050". For example, a pushrod stamped 7.800 and screwed apart one rotation would be 7.800" + .050" = 7.850" gauge length. Therefore, you would order the part number from the catalog that matches this gauge length, since gauge length is how they are listed.
Technique #2
This technique requires one of our Magnum Pushrod Length Checkers. Once fixed, you don’t need to have an expensive gauge or a pair of calipers to measure it. You just need a pushrod of a known length to compare it to (a standard). Then use a pair of common 6" calipers to measure the difference between the standard and yours.
Here are a few final tips for pushrods in general. It is always a good idea to buy a few spares when purchasing a set of custom length pushrods, and stick them in your toolbox. If one ever fails at the track, and you need a replacement, it would be nearly impossible to borrow one from a fellow racer.



Another hint involves cup end pushrods. Measuring them for length is especially difficult, no matter which technique above you choose to use. The size and shape of the cup end varies greatly from manufacturer to manufacturer, so measuring from the ball end to the cup end over the cup surface is a dangerous practice. The best strategy is to drop a 5/16" diameter steel ball into the cup end, and do all measuring over this ball, subtracting the 5/16" diameter (.3125") to calculate the length.





7. How do you check piston to valve clearance?



Step 1:

With the camshaft installed, remove the cylinder head from the block. Clean the combustion chamber and the top of the piston and valve reliefs. The cleaner the piston, the better the clay will stick to it.



Step 2:


Apply a strip of model clay 3/8” to 1/2” wide and approximately 1/4” thick to the pistons. The clay strips should be placed perpendicular (across) to the intake and exhaust valve reliefs (fig. 1). Applying a small amount of oil to the clay will prevent it from sticking to the valves as they press into the clay.



Step 3:

Reinstall the cylinder head with the gasket that is going to be used. It will not be necessary to re-torque the head yet. All head gasket manufacturers can tell you what the compressed thickness of their gasket will be. Measure the gasket before you install it permanently, and add the difference of the gasket thickness to your piston to valve clearance. This will be within .001” or .002” of the exact clearance. Install a sufficient number of head bolts to secure the head in place while you are rotating the engine. Install the pushrods, lifters and rocker arms on the cylinder you have prepared for the clearance check.



Step 4:


Adjust the rocker arms to their suggested clearance. If the camshaft you are checking uses hydraulic lifters, you must temporarily use solid lifters in their place. Hydraulic lifters bleed down and would create a false measurement. Once the hydraulic lifters are replaced with solid lifters, adjust the lash to “zero.” Be sure not to pre-load the valve spring (fig. 2) (be sure to reinstall the hydraulic lifters before starting the engine).



Step 5:

Turn the engine over by hand in the normal direction of rotation. Be sure to rotate the engine over 2 times. This will be one complete revolution of the cam and, it will assure you of an accurate reading on both the intake and exhaust. Remove the cylinder head from the block. Be sure to do this gently, so the clay is not disturbed. It may be stuck to the valves or combustion chamber, so be careful.



Step 6:


With a razor or a sharp knife, slice the clay cleanly, lengthwise through the depression and peel half of it off the piston (fig. 3). The clay’s thickness in the thinnest area will represent the minimum piston to valve clearance.



Step 7:

To accurately check the thickness, use a set of dial calipers (fig. 4). The clay can also be measured close enough with a thin steel rule.



Note: Be sure to check piston to valve clearance after the cam has been degreed in. The positioning of the cam in the engine will greatly affect the piston to valve clearance.







8. How do I degree a camshaft, and why we do we use the Intake Centerline Method instead of valve timing events?



The Intake Centerline Method



There are several accepted ways to degree a camshaft. At COMP Cams®, we feel the Intake Centerline Method is the easiest and most accurate. This method of cam degreeing is very practical and indifferent to design characteristics. It simply involves positioning the center, or point of maximum lift, of the #1 intake lobe with Top Dead Center of the #1 piston.



The Intake Centerline Method still requires accuracy to be correct, but it is somewhat more forgiving. Once you have degreed a camshaft using this method, you will be surprised at its ease. We also recommend positioning the dial indicator on the #1 intake retainer because lift measurements will include any deflection that may occur in the pushrod and rocker arm. This makes the degreeing process as accurate as possible in relation to what actually goes on inside the engine. Before you proceed, you will need a Cam Degree Kit (Part #4796) from COMP Cams®.





Time to Go to Work



Step 1:

The camshaft and timing set have been installed. Make sure that the timing marks on both the cam gear and crank gear are aligned properly, per the cam installation instructions. Use chalk or similar marker to better define the marks.



Step 2:

For example, we have our cam card, and it suggests we install the cam on 106 degree intake centerline. Install all the rocker arms and pushrods in the engine as normal. On the #1 intake lobe, install the solid lifter in place of the hydraulic lifter. If a solid lifter or roller cam is being checked, use that respective lifter. Adjust the #1 intake lash to exactly zero. Do not pre-load the lifter. Next, adjust the #1 exhaust lash to zero. You should be able to turn both pushrods with your fingers easily.



Step 3:

Attach your COMP Cams® pointer (Part #4794) to the block. Many people will make a pointer out of some sort of rigid, yet manageable wire. A stiff coat hanger wire works well.



Step 4:

Attach the degree wheel to the balancer, and install the assembly on the crankshaft
  • There are several ways to attach the degree wheel to the crankshaft. In our example, the degree wheel is mounted to the balancer. The crank may be rotated from either the front or from the flywheel end. Obviously, if the engine is in the car, you must rotate from the front.

  • Remember, the greater the leverage, the smoother the crank rotation, thus more accuracy. NEVER use the starter to turn the engine while degreeing the cam.



Step 5:

Before installing the piston stop, rotate the crankshaft to get the #1 piston in approximate T.D.C. position, with both the intake and exhaust valves closed. This can be a rough guess, but it can save you from making a mistake later. Adjust your pointer to zero or T.D.C. on the degree wheel.



Step 6:

Turn the crankshaft opposite the engine rotation approximately 15-20 degrees. This will lower the position enough to allow the T.D.C. stop to be installed in the spark plug hole. Screw in the piston stop until it touches the piston. (fig. A). Continue to turn the engine in the same direction until the piston comes back up and touches the piston stop. Mark the degree wheel with a pen or pencil on the number the pointer is on (fig. B). Turn the engine in the other direction (same as engine rotation) until the piston comes back up and touches the piston stop. Make a mark on the number the pointer is on (fig. C).



Step 7:

Remove the piston stop after marking the two points on your degree wheel. Rotate the crankshaft to the midpoint of the two marks. This point is T.D.C. for cylinder #1. Without rotating the crankshaft, adjust the degree wheel to read 0 degrees at the pointer (fig. D). You are now ready to locate the intake lobe centerline relative to T.D.C. If you are not absolutely sure that your 0 degree mark is set at T.D.C., repeat this procedure. This step is critical to proper cam alignment.



Step 8:

Attach the dial indicator to the dial indicator mount. Position the dial indicator mount so the tip will contact the retainer of the #1 intake valve (fig. E). It is important that the indicator plunger be parallel to the valve stem. Any variance in the angle of the indicator will introduce geometric errors into the lift readings.



Step 9:

Rotate the engine, in the normal direction of crankshaft rotation, until you reach maximum lift. The dial indicator will change direction at the point of maximum lift. At this point, set the dial to zero (fig. F).



Step 10:

Back the engine up (usually counter-clockwise) until the indicator reads .100”. Turn the engine back in the normal direction of rotation until (usually clockwise) the dial indicator reads .050” before maximum lift. Record the degree wheel reading.



Step 11:

Continue to rotate the engine over in its normal direction of rotation until the indicator goes past zero to .050” on the closing side of maximum lift. Again, record the degree wheel reading.



Step 12:

Add the two numbers together and divide by 2. That number will be the location of maximum lift of the intake lobe in relation to the crank and piston. This is the intake centerline. For example: The first degree wheel reading was 96 degrees. The second reading was 116 degrees. These two numbers (96 +116) added together will be 212. Dividing 212 by 2 will equal 106. Your actual intake centerline is 106 degrees. Reference back to your cam spec card, and we see that the recommended intake centerline for your camshaft is 106 degrees. Everything is where it should be. In the event that your camshaft did not degree in as per manufacturer’s specs, it will be necessary to either advance (move ahead) or retard (move back) the cam to meet suggested intake centerline. Depending on the engine application, there are several different suggested methods for advancing or retarding the camshaft. One common method is by use of a crank gear with multiple keyways, each one being at a slightly different relationship to the gear teeth. A second method is to use off-set bushings that fit on the cam pin and in the cam gear. The off-set will advance or retard the cam depending on how the bushing is placed on the cam pin. Another method is by off-set keys that fit into the crank gear keyway. A more elaborate system uses an adjustable timing gear. Contact COMP Cams® or your local COMP Cams® dealer for the method best suited to your application.



Note: When degreeing a cam, remember to look at the degree wheel as a full 360 degrees, no matter how the degree wheel you’re using is marked. Many degree wheels are marked in 90 degree or 180 degree increments. On wheels that are marked in 90 degree increments, keep in mind that you must continue to count the number of degrees past 90 degrees. Be sure all readings are taken from Top Dead Center. Keep in mind that to advance the cam, you must lower the intake centerline. For example, if our cam has a lobe separation of 110 degrees, the cam is “straight up” when the intake centerline is 110 degrees. Moving the centerline to 106 degrees advances the can 4 degrees. If we change the centerline to 112 degrees, this would be 2 degrees retarded.





9. What is installed height on a head and how does it affect the spring pressure and lift ability?



Basically, it is the height from the bottom of the retainer to the base of the head where the spring sets. Springs have recommended installed heights, and shorting or raising that height will affect the given specs for the spring. Shorting it will add pressure and take away lift ability; raising does just the opposite.





10. How do you properly break in a camshaft and what oils and additives should you use?



Use high zinc oil (such as the COMP Cams® Break-In Oil) with our 159 additive. Vary the RPM of the motor between 2000-2500 RPM for about 25 minutes. Do NOT try to constantly start the motor if you can not get it to fire with a new cam in it.
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]]> COMP Cams Product Tech jjamros http://www.cpgnation.com/forum/comp-cams-top-10-tech-faqs-3773.html Thumpr Cam Development Presentation - An Inside Look http://www.cpgnation.com/forum/thumpr-cam-development-presentation-inside-look-3294-new-post.html Mon, 15 Mar 2010 17:36:56 GMT Click on the PDF file below to learn more about the development of Thumpr Cam line-up. This presentation was given by Brian Reese, VP of Engineering, at the 2010 Hot Rod & Restoration Trade Show. ]]> Click on the PDF file below to learn more about the development of Thumpr Cam line-up. This presentation was given by Brian Reese, VP of Engineering, at the 2010 Hot Rod & Restoration Trade Show.
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]]> COMP Cams Product Tech CPG Marketing http://www.cpgnation.com/forum/thumpr-cam-development-presentation-inside-look-3294.html Special Notes: GM 6.6L Duramax Cam Installation http://www.cpgnation.com/forum/special-notes-gm-6-6l-duramax-3268-new-post.html Fri, 12 Mar 2010 14:57:58 GMT Warning:
COMP Cams always recommends checking piston to valve clearance whenever installing a camshaft. Modern engine design dictates a compact combustion chamber and tight clearances. Tolerance stack or installation errors can result in interference and failure. COMP recommends 0.080” intake and 0.120” exhaust minimum piston to valve clearance in most applications.

Methods:
Best (Head Off) = Uses solid (roller or flat depending on applications) tappets, clay, a razor blade and calipers: Clay around the valve reliefs, install heads with used gaskets, assemble valve train with solid tappets and turn engine over slowly by hand with zero lash on hydraulic applications or recommended hot lash for solid cams. Use razor blade to slice the clay at the deepest indention and measure the thickness with your calipers.

Next Best (Head On) = Uses a solid follower, degree wheel and dial indicator and flowbench springs: Swap out to a solid follower if hydraulic and set lash to zero. For solid roller or flat applications, use the recommended lash. Install flowbench springs. Zero the degree wheel at compression TDC and check clearance at the following angles:

Exhaust = 20 BTDC, 15 BTDC, 10 BTDC and 5 BTDC
Intake = 5 ATDC, 10 ATDC, 15 ATDC and 20 ATDC

Clearance is determined by rotating the engine to the desired location, zeroing the indicator and pushing the retainer down with your hand gently until it contacts the piston, the measurement you have at that point is your piston to valve clearance for that location. Next rotate the engine to the next location and repeat the procedure until you find the closest location. ]]> Warning:

COMP Cams always recommends checking piston to valve clearance whenever installing a camshaft. Modern engine design dictates a compact combustion chamber and tight clearances. Tolerance stack or installation errors can result in interference and failure. COMP recommends 0.080” intake and 0.120” exhaust minimum piston to valve clearance in most applications.



Methods:

Best (Head Off) = Uses solid (roller or flat depending on applications) tappets, clay, a razor blade and calipers: Clay around the valve reliefs, install heads with used gaskets, assemble valve train with solid tappets and turn engine over slowly by hand with zero lash on hydraulic applications or recommended hot lash for solid cams. Use razor blade to slice the clay at the deepest indention and measure the thickness with your calipers.



Next Best (Head On) = Uses a solid follower, degree wheel and dial indicator and flowbench springs: Swap out to a solid follower if hydraulic and set lash to zero. For solid roller or flat applications, use the recommended lash. Install flowbench springs. Zero the degree wheel at compression TDC and check clearance at the following angles:



Exhaust = 20 BTDC, 15 BTDC, 10 BTDC and 5 BTDC

Intake = 5 ATDC, 10 ATDC, 15 ATDC and 20 ATDC



Clearance is determined by rotating the engine to the desired location, zeroing the indicator and pushing the retainer down with your hand gently until it contacts the piston, the measurement you have at that point is your piston to valve clearance for that location. Next rotate the engine to the next location and repeat the procedure until you find the closest location.
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]]> COMP Cams Product Tech CPG Marketing http://www.cpgnation.com/forum/special-notes-gm-6-6l-duramax-3268.html COMP Cams® Pushrod Tech http://www.cpgnation.com/forum/comp-cams-pushrod-tech-2662-new-post.html Tue, 01 Sep 2009 22:14:05 GMT As cam profiles continue to get more aggressive and valve springs pressure increase, the importance of pushrod knowledge has never been more critical. Here are some answers to the most common questions that you might have for COMP Cams® tech support about pushrods.

Pushrod Length & Rocker Arm Geometry

A large number of variables are involved in determining the correct length pushrod for your application. Pushrod length is affected by any of the following:
• Block deck height
• Head deck height
• Head stud boss height
• Rocker arm brand/design
• Cam base circle size
• Lifter design/brand/pushrod seat height
• Valve stem length
Don’t assume anything when determining the right pushrod for your new engine. A pushrod that fits one engine may not necessarily work in another. Any number of items can be different on your engine, requiring you to use a different pushrod length. Following the steps below will streamline the pushrod selection process, ensuring that you get the right parts the first time.

1. Buy a checking pushrod.

Do not buy pushrods when you buy the cam, lifters and other valve train components. As much as we would like to sell you pushrods at this time, nobody can predict ahead of time what length a given engine needs, unless it is bone stock.

Instead, invest in a checking pushrod at this time. They are available in two different designs, with the more expensive of the two being easier to measure once you have it adjusted to the proper length for your valve train. Neither is particularly expensive if you consider time lost and freight costs when returning pushrods.

Other companies offer their own versions of pushrod length checking devices, funny little plastic things with complicated instructions to calculate the length. The main disadvantage with these is that you have to order the pushrods and receive them before you know if your calculations are correct. With a checking pushrod, you can actually rotate the motor over and check the rocker arm/valve tip relationship as you adjust the pushrod length. When you get the correct geometry, it is a simple matter then to measure the length and place an order. COMP Cams® carries a large number of various length and diameter pushrods so you get the correct length the first time.

2. Determine correct valve train geometry.

What is the correct length pushrod for your application? The one that produces correct valve train geometry. What is correct valve train geometry? When the rocker arm roller tip rolls from the intake side of the valve tip, across the center of the tip (at approximately mid-lift), to the exhaust side of the valve tip (at full lift) and back. See Diagram A.

3. Measure the resulting pushrod.

Measuring the length of a pushrod is a simple process. The most important thing to remember is that different manufacturers measure pushrods differently. Not all pushrods of a stated length will measure exactly the same. The three most common pushrod measurements are shown in Diagram B.

Theoretical Length: This assumes that the pushrod has no oil hole in the end of it. Therefore, the radius at either end is complete, which lengthens the pushrod approximately .017" in the case of a 5/16" pushrod with .100" diameter oil holes, minimally chamfered.

Actual Length: This is what you would measure if you had a set of calipers large enough to measure over the oil holes at each end of the pushrod. This is the measurement that most people can relate to. Unfortunately, this measurement is affected not only by the diameter of the oil holes but also by the entrance chamfer for each oil hole.

Gauge Length: Although the most difficult to measure (it requires a special length checking gauge), this measurement is the most reliable. This is because the oil holes and their chamfers are eliminated from the measurement. The only problem is that not all companies use the same gauge diameter. COMP Cams® uses a .140" gauge diameter. All Magnum and Hi-Tech™ Pushrods listed in this catalog are measured using this technique. See Diagram B on the following page.

4. Simple measurement techniques.

We realize that most people don’t have access to the special gauge required for these measurements or even a dial caliper large enough for most pushrods. We’ve developed two techniques to help you determine exact pushrod length so that the perfect valve train geometry is achieved in your engine.


Pushrod Measurement Techniques

Technique #1

This technique requires the use of a COMP Cams® Hi-Tech™ Pushrod Length Checker. These are marked with a standard length stamped in them. This number represents the gauge length of the part (.140" gauge diameter) with the two halves screwed completely together. Extending the pushrod one rotation lengthens the gauge length .050". For example, a pushrod stamped 7.800 and screwed apart one rotation would be 7.800" + .050" = 7.850" gauge length. Therefore you would order the part number from the catalog that matches this gauge length, since gauge length is how they are listed.

Technique #2

This technique requires one of our Magnum Pushrod Length Checkers. Once fixed, you don’t need to have an expensive gauge or a pair of calipers to measure it. You just need a pushrod of a known length to compare it to (a standard). Then use a pair of common 6" calipers to measure the difference between the standard and yours.

Here are a few final hints about pushrods in general. It is always a good idea to buy a few spares when purchasing a set of custom length pushrods, and stick them in your toolbox. If one ever fails at the track and you need a replacement, it would be nearly impossible to borrow one from a fellow racer.

Another hint involves cup end pushrods. Measuring them for length is especially difficult, no matter which technique above you choose to use. The size and shape of the cup end varies greatly from manufacturer to manufacturer, so measuring from the ball end to the cup end over the cup surface is a dangerous practice. The best strategy is to drop a 5/16" diameter steel ball into the cup end, and do all measuring over this ball, subtracting the 5/16" diameter (.3125") to figure the length.


For help selecting the correct series pushrod for your application call CAM HELP® at 1-800-999-0853 of check out the COMP Cams® website. ]]> As cam profiles continue to get more aggressive and valve springs pressure increase, the importance of pushrod knowledge has never been more critical. Here are some answers to the most common questions that you might have for COMP Cams® tech support about pushrods.



Pushrod Length & Rocker Arm Geometry



A large number of variables are involved in determining the correct length pushrod for your application. Pushrod length is affected by any of the following:

• Block deck height

• Head deck height

• Head stud boss height

• Rocker arm brand/design

• Cam base circle size

• Lifter design/brand/pushrod seat height

• Valve stem length
Don’t assume anything when determining the right pushrod for your new engine. A pushrod that fits one engine may not necessarily work in another. Any number of items can be different on your engine, requiring you to use a different pushrod length. Following the steps below will streamline the pushrod selection process, ensuring that you get the right parts the first time.



1. Buy a checking pushrod.



Do not buy pushrods when you buy the cam, lifters and other valve train components. As much as we would like to sell you pushrods at this time, nobody can predict ahead of time what length a given engine needs, unless it is bone stock.



Instead, invest in a checking pushrod at this time. They are available in two different designs, with the more expensive of the two being easier to measure once you have it adjusted to the proper length for your valve train. Neither is particularly expensive if you consider time lost and freight costs when returning pushrods.



Other companies offer their own versions of pushrod length checking devices, funny little plastic things with complicated instructions to calculate the length. The main disadvantage with these is that you have to order the pushrods and receive them before you know if your calculations are correct. With a checking pushrod, you can actually rotate the motor over and check the rocker arm/valve tip relationship as you adjust the pushrod length. When you get the correct geometry, it is a simple matter then to measure the length and place an order. COMP Cams® carries a large number of various length and diameter pushrods so you get the correct length the first time.



2. Determine correct valve train geometry.



What is the correct length pushrod for your application? The one that produces correct valve train geometry. What is correct valve train geometry? When the rocker arm roller tip rolls from the intake side of the valve tip, across the center of the tip (at approximately mid-lift), to the exhaust side of the valve tip (at full lift) and back. See Diagram A.



3. Measure the resulting pushrod.



Measuring the length of a pushrod is a simple process. The most important thing to remember is that different manufacturers measure pushrods differently. Not all pushrods of a stated length will measure exactly the same. The three most common pushrod measurements are shown in Diagram B.



Theoretical Length: This assumes that the pushrod has no oil hole in the end of it. Therefore, the radius at either end is complete, which lengthens the pushrod approximately .017" in the case of a 5/16" pushrod with .100" diameter oil holes, minimally chamfered.



Actual Length: This is what you would measure if you had a set of calipers large enough to measure over the oil holes at each end of the pushrod. This is the measurement that most people can relate to. Unfortunately, this measurement is affected not only by the diameter of the oil holes but also by the entrance chamfer for each oil hole.



Gauge Length: Although the most difficult to measure (it requires a special length checking gauge), this measurement is the most reliable. This is because the oil holes and their chamfers are eliminated from the measurement. The only problem is that not all companies use the same gauge diameter. COMP Cams® uses a .140" gauge diameter. All Magnum and Hi-Tech™ Pushrods listed in this catalog are measured using this technique. See Diagram B on the following page.



4. Simple measurement techniques.



We realize that most people don’t have access to the special gauge required for these measurements or even a dial caliper large enough for most pushrods. We’ve developed two techniques to help you determine exact pushrod length so that the perfect valve train geometry is achieved in your engine.





Pushrod Measurement Techniques



Technique #1



This technique requires the use of a COMP Cams® Hi-Tech™ Pushrod Length Checker. These are marked with a standard length stamped in them. This number represents the gauge length of the part (.140" gauge diameter) with the two halves screwed completely together. Extending the pushrod one rotation lengthens the gauge length .050". For example, a pushrod stamped 7.800 and screwed apart one rotation would be 7.800" + .050" = 7.850" gauge length. Therefore you would order the part number from the catalog that matches this gauge length, since gauge length is how they are listed.



Technique #2



This technique requires one of our Magnum Pushrod Length Checkers. Once fixed, you don’t need to have an expensive gauge or a pair of calipers to measure it. You just need a pushrod of a known length to compare it to (a standard). Then use a pair of common 6" calipers to measure the difference between the standard and yours.



Here are a few final hints about pushrods in general. It is always a good idea to buy a few spares when purchasing a set of custom length pushrods, and stick them in your toolbox. If one ever fails at the track and you need a replacement, it would be nearly impossible to borrow one from a fellow racer.



Another hint involves cup end pushrods. Measuring them for length is especially difficult, no matter which technique above you choose to use. The size and shape of the cup end varies greatly from manufacturer to manufacturer, so measuring from the ball end to the cup end over the cup surface is a dangerous practice. The best strategy is to drop a 5/16" diameter steel ball into the cup end, and do all measuring over this ball, subtracting the 5/16" diameter (.3125") to figure the length.





For help selecting the correct series pushrod for your application call CAM HELP® at 1-800-999-0853 of check out the COMP Cams® website.
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]]> COMP Cams Product Tech jbarker http://www.cpgnation.com/forum/comp-cams-pushrod-tech-2662.html The Truth About Valve Springs http://www.cpgnation.com/forum/truth-about-valve-springs-2631-new-post.html Tue, 01 Sep 2009 15:28:24 GMT Valve springs are one of the most critical and most overlooked components in your engine. Proper selection of the valve spring begins with identifying the application and selecting all of the valve train components to achieve the engine builders’ goals.

The spring is selected to complement the system and must be matched with the entire valve train in order for the engine to reach its full potential. It does absolutely no good to install a cam that will rpm to 8000 if you do not have the correct springs. Improper selection of the wrong valve spring is one of the most common causes of engine failure. Other common causes are the incorrect installation and improper handling of the valve springs.

Selecting a Spring
1. Use only the valve springs that will give the correct spring pressure with the valve both on the seat and at maximum lift.

2. The outside diameter of the recommended valve spring may require that the spring pocket of the head be machined to a bigger size.

3. One of the easiest and sometimes most costly mistakes made in racing engines is not positively locating the spring. A valve spring that “dances” around on the cylinder head or retainer causes harmful harmonics and excessive wear. A spring that is forced onto a retainer is likely to fail at that coil. That is why we have such a large selection of steel and titanium retainers, hardened steel spring seat cups and I.D. locators to better match our springs. A spring that is contained properly at the retainer and the cylinder head will offer the longest possible service life.
Proper Spring Handling
1. Handle springs with care. Never place in a vise, grab with pliers or hit them with a hammer. This will damage the surface of the spring, which will cause a spring to fail.

2. When separating double or triple springs, use only a durable plastic object that cannot harm the shot-peened surface of the spring. Never use a tool or hard metal object like a screwdriver.


3. Valve springs are shipped with a rust preventative coating that should remain on the spring throughout engine assembly. Do not clean springs with acidic or evaporative cleaners. This causes rapid drying and promotes the formation of rust on the surface, which can cause catastrophic failures. Even a slight amount of corrosion can grow to be a problem.

4. When installing springs, use COMP Cams® Valve Train Assembly Spray (Part #106) to ease assembly and improve the life of the spring.
Checking Loads
1. COMP Cams® has matched each set of springs for load consistency. A variance of + or -10% is acceptable for new springs.

2. When checking the spring loads on a load tester (Part #5313) measure and note the thickness of the retainer where the outer spring sits. Assemble the retainer on the spring and place on the base of the spring checker.

3. Compress the spring to the desired installed height. This is the measurement between the top of the spring (on the bottom side of the retainer where the outer spring sits) and the bottom of the spring on the base.
* NOTE *
Since the retainer is installed in the spring when checking the spring loads, make certain that the thickness of the retainer is not included when calculating the installed height and is accounted for when compressing the spring. The spring load checker will show to be higher with the spring installed at the correct height.


Installation
1. Before installing the spring on the cylinder heads, check the installed spring height (Diagram A). This is the distance from the bottom of the retainer to the surface where the spring rests on the head. The valves, retainers and valve locks will be used in this step. First, install the valve in the guide, then install the retainer and valve locks. Pull the retainer tightly against the valve locks while holding the valve assembly steady.
Measure the distance between the spring seat and the outside step of the retainer using your height micrometer (Part #4928 or #4929) or a snap gauge and a pair of calipers. Repeat this procedure for all the valves and record your Information. After you have measured all the valves, find the shortest height. This will become the spring’s installed height on your heads. If your combination includes a dual or triple spring assembly, it will be necessary to allow for the inner steps of the retainer.

2. Once you have determined the shortest installed height, it will be necessary to use shims to obtain this height (±.020” is acceptable) on the remaining valves. These are available through our catalog or at any of
your local COMP Cams® dealers.

3. Before removing the retainers, measure the distance from the bottom of the retainer to the top of the valve seal (Diagram A). This distance must be greater than the lift of the valve. If not, the guide must be machined. This is a very common cause of early camshaft failure.

4. Once the valve springs have been installed, it is important to check for coil bind. This means that when the valve is fully open, there must be a minimum of .060” clearance between the coils of both the inner and outer springs. If this clearance does not exist, you must change either the retainer or the valve to gain more installed height, or change to a spring that will handle more lift or machine the spring seat for extra depth.

5. Always check for clearance between the retainer and the inside face of the rocker arm. This will be most evident while the valve is on the seat. Rocker arms are designed to clear specific spring diameters, so you should check to see that you have the proper rocker arm/retainer combination. This situation can also be the result of improper rocker geometry and may be corrected with different length pushrods or a different length valve.

6. To aid in the engine breaking process, spray the springs, rocker arms and pushrods with COMP Cams® Valve Train Assembly Spray (Part #106).

Breaking In a Spring

1. It is important for new springs to take a heat-set. Never abuse or run the engine at high rpm when the springs are new. Upon initial start-up, limit rpm to 1500 to 2000 until the temperature has reached operating levels. Shut off the engine and allow the springs to cool to room temperature. This usually will eliminate early breakage and prolong spring life. After the spring has been “broken-in”, it is common for it to lose a slight amount of pressure. Once this initial pressure loss occurs, the spring pressure should remain constant unless the engine is abused and the spring becomes overstressed. Then the springs must either be replaced or shimmed to the correct pressure.

Check out the COMP Cams® website!
]]> Valve springs are one of the most critical and most overlooked components in your engine. Proper selection of the valve spring begins with identifying the application and selecting all of the valve train components to achieve the engine builders’ goals.



The spring is selected to complement the system and must be matched with the entire valve train in order for the engine to reach its full potential. It does absolutely no good to install a cam that will rpm to 8000 if you do not have the correct springs. Improper selection of the wrong valve spring is one of the most common causes of engine failure. Other common causes are the incorrect installation and improper handling of the valve springs.



Selecting a Spring

1. Use only the valve springs that will give the correct spring pressure with the valve both on the seat and at maximum lift.



2. The outside diameter of the recommended valve spring may require that the spring pocket of the head be machined to a bigger size.



3. One of the easiest and sometimes most costly mistakes made in racing engines is not positively locating the spring. A valve spring that “dances” around on the cylinder head or retainer causes harmful harmonics and excessive wear. A spring that is forced onto a retainer is likely to fail at that coil. That is why we have such a large selection of steel and titanium retainers, hardened steel spring seat cups and I.D. locators to better match our springs. A spring that is contained properly at the retainer and the cylinder head will offer the longest possible service life.
Proper Spring Handling

1. Handle springs with care. Never place in a vise, grab with pliers or hit them with a hammer. This will damage the surface of the spring, which will cause a spring to fail.



2. When separating double or triple springs, use only a durable plastic object that cannot harm the shot-peened surface of the spring. Never use a tool or hard metal object like a screwdriver.





3. Valve springs are shipped with a rust preventative coating that should remain on the spring throughout engine assembly. Do not clean springs with acidic or evaporative cleaners. This causes rapid drying and promotes the formation of rust on the surface, which can cause catastrophic failures. Even a slight amount of corrosion can grow to be a problem.



4. When installing springs, use COMP Cams® Valve Train Assembly Spray (Part #106) to ease assembly and improve the life of the spring.
Checking Loads

1. COMP Cams® has matched each set of springs for load consistency. A variance of + or -10% is acceptable for new springs.



2. When checking the spring loads on a load tester (Part #5313) measure and note the thickness of the retainer where the outer spring sits. Assemble the retainer on the spring and place on the base of the spring checker.



3. Compress the spring to the desired installed height. This is the measurement between the top of the spring (on the bottom side of the retainer where the outer spring sits) and the bottom of the spring on the base.

* NOTE *

Since the retainer is installed in the spring when checking the spring loads, make certain that the thickness of the retainer is not included when calculating the installed height and is accounted for when compressing the spring. The spring load checker will show to be higher with the spring installed at the correct height.





Installation

1. Before installing the spring on the cylinder heads, check the installed spring height (Diagram A). This is the distance from the bottom of the retainer to the surface where the spring rests on the head. The valves, retainers and valve locks will be used in this step. First, install the valve in the guide, then install the retainer and valve locks. Pull the retainer tightly against the valve locks while holding the valve assembly steady.

Measure the distance between the spring seat and the outside step of the retainer using your height micrometer (Part #4928 or #4929) or a snap gauge and a pair of calipers. Repeat this procedure for all the valves and record your Information. After you have measured all the valves, find the shortest height. This will become the spring’s installed height on your heads. If your combination includes a dual or triple spring assembly, it will be necessary to allow for the inner steps of the retainer.



2. Once you have determined the shortest installed height, it will be necessary to use shims to obtain this height (±.020” is acceptable) on the remaining valves. These are available through our catalog or at any of

your local COMP Cams® dealers.



3. Before removing the retainers, measure the distance from the bottom of the retainer to the top of the valve seal (Diagram A). This distance must be greater than the lift of the valve. If not, the guide must be machined. This is a very common cause of early camshaft failure.



4. Once the valve springs have been installed, it is important to check for coil bind. This means that when the valve is fully open, there must be a minimum of .060” clearance between the coils of both the inner and outer springs. If this clearance does not exist, you must change either the retainer or the valve to gain more installed height, or change to a spring that will handle more lift or machine the spring seat for extra depth.



5. Always check for clearance between the retainer and the inside face of the rocker arm. This will be most evident while the valve is on the seat. Rocker arms are designed to clear specific spring diameters, so you should check to see that you have the proper rocker arm/retainer combination. This situation can also be the result of improper rocker geometry and may be corrected with different length pushrods or a different length valve.



6. To aid in the engine breaking process, spray the springs, rocker arms and pushrods with COMP Cams® Valve Train Assembly Spray (Part #106).


Breaking In a Spring



1. It is important for new springs to take a heat-set. Never abuse or run the engine at high rpm when the springs are new. Upon initial start-up, limit rpm to 1500 to 2000 until the temperature has reached operating levels. Shut off the engine and allow the springs to cool to room temperature. This usually will eliminate early breakage and prolong spring life. After the spring has been “broken-in”, it is common for it to lose a slight amount of pressure. Once this initial pressure loss occurs, the spring pressure should remain constant unless the engine is abused and the spring becomes overstressed. Then the springs must either be replaced or shimmed to the correct pressure.



Check out the COMP Cams® website!

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]]> COMP Cams Product Tech jbarker http://www.cpgnation.com/forum/truth-about-valve-springs-2631.html Effects Of Changes In Cam Timing And Lobe Separation Angle http://www.cpgnation.com/forum/effects-changes-cam-timing-lobe-separation-2630-new-post.html Tue, 01 Sep 2009 15:07:22 GMT The following tables illustrate how variations in lobe separation angle and camshaft
timing will effect the behavior of the engine in which the camshaft is installed.




Check out the COMP Cams® website! ]]> The following tables illustrate how variations in lobe separation angle and camshaft

timing will effect the behavior of the engine in which the camshaft is installed.









Check out the COMP Cams® website!
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]]> COMP Cams Product Tech jbarker http://www.cpgnation.com/forum/effects-changes-cam-timing-lobe-separation-2630.html COMP Cams® Lifter Tech http://www.cpgnation.com/forum/comp-cams-lifter-tech-2629-new-post.html Tue, 01 Sep 2009 13:56:49 GMT For years COMP Cams® lifters have set the standard for solid roller lifter technology, but today’s engine’s place an even greater demand on lifters. With today’s aggressive cam designs and increased rpm ranges, look to COMP Cams® Endure-X™ Solid Roller Lifters or the new Elite Race™ Solid Roller Lifters.

[IMGLFT=]http://www.cpgnation.com/filehost/files/8/800-2.jpg[/IMGLFT][IMGRT=]http://www.cpgnation.com/filehost/files/8/875-2.jpg[/IMGRT]






















Flat Tappet vs. Roller Tappet Lifters

In nearly all circumstances, a good roller camshaft design will outperform its flat tappet counterpart. Among the benefits of roller cams are higher tappet velocity, more lift and more area, along with reduced valve train friction (often a 15+ hp increase) and higher engine rpm with little effect on low speed drivability and power.

Roller tappets are also reusable, which makes it possible to swap just the camshaft without the expense of new lifters. And finally, roller tappets are far less prone to wear, allowing higher spring loads, and they are more consistent with today’s oils.

The biggest advantage with a flat tappet cam and lifters is the upfront cost. It can be significantly less expensive to use a flat tappet setup but should you decide to install a new camshaft, flat tappets are not reusable. You will need new lifters as well.

Hydraulic vs. Mechanical (Solid) Lifters

Both lifter types look the same from the outside, with both having pushrod seats held in by a retaining clip. In a hydraulic lifter the seat moves by means of a hydraulic valve and oil pressure within the lifter. The mechanical lifter does not have a valve and is solid.

The pushrod seat in a solid lifter sits upon an internal step inside the lifter body, preventing it from moving. The hydraulic lifter, on the other hand, has a pushrod seat that sits on top of a moveable hydraulic mechanism which acts like a tiny hydraulic pump. Below this mechanism are a valve and a spring to produce an upward force, moving the seat up against the pushrod when the lifter is on the base circle.

Solid cam designs require a running clearance or “valve lash”. Hydraulic cams are the exact opposite. In a standard hydraulic lifter the pushrod takes up all of the clearance and submerges into the lifter’s pushrod seat approximately .020"-.070". The distance that the pushrod submerges is known as the “pre-load”.


Setting Valve Lash With A Solid Lifter Camshaft

First, check the spec card that came with your cam for the correct valve lash specifications. All COMP Cams® valve lash settings are “hot” settings (set at normal engine operating temperature) but will work for initial start-up as well.

Turn the crankshaft in the direction of normal engine rotation until the exhaust pushrod of the cylinder you are adjusting begins to move upward, opening the valve. Adjust the INTAKE lash by tightening the intake rocker nut with the correct thickness feeler gauge inserted between the valve stem and the rocker tip. Tighten the rocker nut until there is a slight drag when moving the feeler gauge. Next, rotate the engine until the intake pushrod fully opens the valve and then goes half-way back down. Adjust the EXHAUST rocker nut (with correct feeler gauge) using the same procedure. Repeat for all cylinders.

After setting your valve lash with the engine cold, start it and follow the appropriate break-in procedures. Due to thermal expansion, your valve lash will now be tighter than it was when the engine was cold. Repeat the adjustment process to ensure that your valve lash matches that specified by your cam card at normal operating temperature.
Note: Check with COMP Cams® on valve lash settings if using aluminum heads or blocks.
Setting Hydraulic Lifter Pre-load (Adjustable Valve Train)

When installing a hydraulic cam, lifters or rocker arms, establishing the correct lifter pre-load improves both performance and engine life. Insufficient pre-load will create excessive valve train noise and wear. Excessive pre-load will cause rough idling and low manifold vacuum, and can even lead to severe engine damage. With an adjustable valve train, proceed as follows:

Install the pushrods and rocker arms. Be sure the pushrods are seated correctly in the lifter and rocker arm. Turn the engine over in the direction of rotation until the EXHAUST pushrod just begins to move upward, opening the valve. Now adjust the INTAKE rocker of that cylinder. Carefully tighten the nut on the intake rocker while spinning the pushrod with your fingertips. You will feel a slight resistance in the pushrod when you have taken up all of the clearance. This is “zero lash.” Turn the adjusting nut to the specified pre-load – typically 1/4-3/4 of a turn, but this will vary based on the lifter number.

Turn the engine in its rotation direction until the intake pushrod comes all the way up and almost all the way back down. Now set the EXHAUST rocker to “zero lash” and add the specified pre-load. Repeat this process for all remaining cylinders.

Setting Hydraulic Lifter Pre-load (Non-Adjustable Valve Train)

COMP Cams® recommends using an adjustable pushrod to check the pre-load. Typically, only one cylinder needs to be checked in this process. After applying lube, install the adjustable pushrods and assemble the valve train. Using the same procedure mentioned earlier, adjust the intake and exhaust valves to zero lash by changing the length of the adjustable pushrod for precise fitment. Order a pushrod that is .020"-.070" longer than the pushrod length at zero lash to ensure the proper pre-load.

Check out the COMP Cams® website!
]]> For years COMP Cams® lifters have set the standard for solid roller lifter technology, but today’s engine’s place an even greater demand on lifters. With today’s aggressive cam designs and increased rpm ranges, look to COMP Cams® Endure-X™ Solid Roller Lifters or the new Elite Race™ Solid Roller Lifters.



[IMGLFT=]http://www.cpgnation.com/filehost/files/8/800-2.jpg[/IMGLFT][IMGRT=]http://www.cpgnation.com/filehost/files/8/875-2.jpg[/IMGRT]













































Flat Tappet vs. Roller Tappet Lifters



In nearly all circumstances, a good roller camshaft design will outperform its flat tappet counterpart. Among the benefits of roller cams are higher tappet velocity, more lift and more area, along with reduced valve train friction (often a 15+ hp increase) and higher engine rpm with little effect on low speed drivability and power.



Roller tappets are also reusable, which makes it possible to swap just the camshaft without the expense of new lifters. And finally, roller tappets are far less prone to wear, allowing higher spring loads, and they are more consistent with today’s oils.



The biggest advantage with a flat tappet cam and lifters is the upfront cost. It can be significantly less expensive to use a flat tappet setup but should you decide to install a new camshaft, flat tappets are not reusable. You will need new lifters as well.



Hydraulic vs. Mechanical (Solid) Lifters



Both lifter types look the same from the outside, with both having pushrod seats held in by a retaining clip. In a hydraulic lifter the seat moves by means of a hydraulic valve and oil pressure within the lifter. The mechanical lifter does not have a valve and is solid.



The pushrod seat in a solid lifter sits upon an internal step inside the lifter body, preventing it from moving. The hydraulic lifter, on the other hand, has a pushrod seat that sits on top of a moveable hydraulic mechanism which acts like a tiny hydraulic pump. Below this mechanism are a valve and a spring to produce an upward force, moving the seat up against the pushrod when the lifter is on the base circle.



Solid cam designs require a running clearance or “valve lash”. Hydraulic cams are the exact opposite. In a standard hydraulic lifter the pushrod takes up all of the clearance and submerges into the lifter’s pushrod seat approximately .020"-.070". The distance that the pushrod submerges is known as the “pre-load”.





Setting Valve Lash With A Solid Lifter Camshaft



First, check the spec card that came with your cam for the correct valve lash specifications. All COMP Cams® valve lash settings are “hot” settings (set at normal engine operating temperature) but will work for initial start-up as well.



Turn the crankshaft in the direction of normal engine rotation until the exhaust pushrod of the cylinder you are adjusting begins to move upward, opening the valve. Adjust the INTAKE lash by tightening the intake rocker nut with the correct thickness feeler gauge inserted between the valve stem and the rocker tip. Tighten the rocker nut until there is a slight drag when moving the feeler gauge. Next, rotate the engine until the intake pushrod fully opens the valve and then goes half-way back down. Adjust the EXHAUST rocker nut (with correct feeler gauge) using the same procedure. Repeat for all cylinders.



After setting your valve lash with the engine cold, start it and follow the appropriate break-in procedures. Due to thermal expansion, your valve lash will now be tighter than it was when the engine was cold. Repeat the adjustment process to ensure that your valve lash matches that specified by your cam card at normal operating temperature.

Note: Check with COMP Cams® on valve lash settings if using aluminum heads or blocks.
Setting Hydraulic Lifter Pre-load (Adjustable Valve Train)



When installing a hydraulic cam, lifters or rocker arms, establishing the correct lifter pre-load improves both performance and engine life. Insufficient pre-load will create excessive valve train noise and wear. Excessive pre-load will cause rough idling and low manifold vacuum, and can even lead to severe engine damage. With an adjustable valve train, proceed as follows:



Install the pushrods and rocker arms. Be sure the pushrods are seated correctly in the lifter and rocker arm. Turn the engine over in the direction of rotation until the EXHAUST pushrod just begins to move upward, opening the valve. Now adjust the INTAKE rocker of that cylinder. Carefully tighten the nut on the intake rocker while spinning the pushrod with your fingertips. You will feel a slight resistance in the pushrod when you have taken up all of the clearance. This is “zero lash.” Turn the adjusting nut to the specified pre-load – typically 1/4-3/4 of a turn, but this will vary based on the lifter number.



Turn the engine in its rotation direction until the intake pushrod comes all the way up and almost all the way back down. Now set the EXHAUST rocker to “zero lash” and add the specified pre-load. Repeat this process for all remaining cylinders.



Setting Hydraulic Lifter Pre-load (Non-Adjustable Valve Train)



COMP Cams® recommends using an adjustable pushrod to check the pre-load. Typically, only one cylinder needs to be checked in this process. After applying lube, install the adjustable pushrods and assemble the valve train. Using the same procedure mentioned earlier, adjust the intake and exhaust valves to zero lash by changing the length of the adjustable pushrod for precise fitment. Order a pushrod that is .020"-.070" longer than the pushrod length at zero lash to ensure the proper pre-load.



Check out the COMP Cams® website!

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]]> COMP Cams Product Tech jbarker http://www.cpgnation.com/forum/comp-cams-lifter-tech-2629.html