Converting a Tried-and-True Small Block Chevy from a Flat Tappet to a Roller Camshaft
There aren’t many cutting edge ideas associated with the small block Chevy, as it’s been in the hot rod rotation for 60 years now. However, it still stands at the most popular engine platform, whether you’re dealing with a street rod, a drag car or a rowdy street machine. Although the platform has remained the same, a lot of the internals are leaps and bounds ahead of the original equipment. For instance, camshaft and valve train technology has allowed gear heads to use parts and pieces that were once considered hardcore racing components in their weekend cruisers.
It’s quite common for a mild mannered small block Chevy to have a roller camshaft and valve train. We want to illustrate the necessary steps involved in converting a hydraulic flat tappet camshaft to a hydraulic roller, using the common small block Chevy as an example.
Our project car drove into the shop under its own power, but had developed some excessive valve train noise. The car is a 1964 Corvette, and the engine is a 350ci small block Chevy with a mild mix of modifications, which made for an excellent street car with a little more pep than your average weekend cruiser.
With flattop pistons, Dart Pro1 Platinum 200cc heads and a Dart dual plane intake, the engine had a mis-matched camshaft profile, due to previous plans that never materialized. The camshaft in question is a COMP Cams NX274H camshaft, which is designed for use with nitrous oxide and features a 230/244 duration split at .050-inch lift, and a max lift of .487/.501-inch. Along with the big split in duration and valve lift, the nitrous-ready camshaft features a 113-degree lobe separation angle. It is a flat tappet design, with High Energy hydraulic lifters, hardened pushrods and 1.6 Ultra Gold rocker arms, all from COMP Cams.
With plenty of miles and abuse on the combination, it was time for a mild overhaul, which included pulling the cylinder heads and removing all of the valve train to replace it with a new COMP Cams hydraulic roller setup.
“The goal is to free up a few horsepower with reduced friction, while also matching the camshaft profile to the engine’s current specifications.”
While a camshaft swap seems pretty simple, it’s important to note that it’s more than just sticking a new camshaft in the block and re-assembling the engine. There are a few additional parts, as well as additional assembly steps required to make sure the roller camshaft lasts a long time in our small block.
When we decided it was time to refresh the engine, we consulted the folks at COMP Cams to determine the correct parts for the job. We didn’t want to go too radical on the camshaft, and we obviously didn’t want a lot of maintenance, since the car sees quite a few street miles. The answer is a COMP Cams Xtreme Energy 282 hydraulic roller camshaft (XR282HR), and the guys at COMP supplied us with all of the related part numbers, and other suggested parts to get our engine back on the road. And though it was a pretty time-consuming job to convert our small block from flat tappet to roller, we could see the time, effort and money was worth it as soon as we fired the engine.
Now, we have a freshened engine with a new attitude, thanks to a better match-up on the camshaft and valve train components. We’ve highlighted the necessary steps to convert your small block from a flat tappet camshaft to a hydraulic roller, so follow along with our build and consult the tech guys at COMP Cams for further advice on camshaft selection. We’ve also included a parts list at the end of the article.
The subject at hand is a mildly modified 350ci small block Chevy. The engine has served several years of street duty, but developed some valve train noise after a harsh life. We plan to give a breath of fresh air by swapping the hydraulic flat tappet camshaft for a complete COMP Cams hydraulic roller setup.
Disassembly is always the easy part. A good evening in the shop should result in what you see here. We only noticed one small issue with a rocker arm and pushrod, which may have been causing the noise. Everything else checked out great for an engine with hard miles on it.
The COMP Cams High Energy flat tappet lifters are still in good working order, but we’re swapping them for a set of hydraulic roller lifters to take some stress off the valvetrain and free up a few horsepower.
During our previous build, we used COMP Cams valve springs, but this time, we ordered the complete cam kit, which included new springs, locks and retainers. While we have the engine torn down this far, it’s in our best interest to yank the cylinder heads and have a local machine shop check them out.
Our mild small block had an old school Erson gear drive, which features a fixed idler gear and a cool aluminum timing cover. We’ll be swapping this setup for a COMP Cams timing chain set, and a new aluminum cover, also from COMP.
The previous timing cover had a fixed timing mark pointer, and we didn’t realize it was off by a few degrees until we removed the cover. Notice the dots on the crankshaft gear and camshaft gear are not lined up. That means every time we put the engine “on the mark” for timing, valve adjustments, etc., it wasn’t actually on top dead center.
Before we can pull the camshaft out of the block, we need to remove the fuel pump, as the fuel pump pushrod will prevent the camshaft from coming all the way out of the block.
We kept the cam gear installed to provide a “handle” on the camshaft, making for easy removal. Be careful not to knick any of the cam bearing on the way out. If you feel any type of resistance, do not force it, as you may damage the bearings. The cam bearings cannot be replaced with the engine assembled, so this is a pretty important reminder.
Our COMP Cams Xtreme Energy Hydraulic Roller Retro-Fit kit (K12-432-8) came with a XR282HR camshaft, 853-16 lifters, 2100 timing set, 7809-16 pushrods (not pictured), 986-16 valve springs, and new valve locks, seals and retainers
The XR282HR camshaft is a hydraulic roller design that is designed for retro-fit applications. The camshaft features 230 degrees of duration on the intake side and 236 degrees on the exhaust side, measured at .050-inch lift. Max lift is .510-inch on the intake lobes and .520-inch on the exhaust, when using 1.5:1 rocker arms. Lobe separation angle is 110 degrees, compared to our previous camshaft, which had an LSA of 113 degrees.
We used the timing sprocket as a handle and started sliding the new camshaft into place. We coated the journals with heavy weight motor oil, while the lobes are coated with COMP Cams installation lube.
With the camshaft in place, the next step is to install the timing set, and eventually the timing chain cover. A strong timing chain cover is essential to setting the camshaft end play, which is very important with a roller camshaft.
The base for the timing chain cover can be installed, using the two allen-head bolts supplied with the kit. Although the outer plate may be removed several times to dial in the camshaft endplay, this base will not be removed, so we installed the gasket between the block and base.
It’s important to have a super clean mounting surface to get a proper measurement on endplay, so we used brake cleaner and a rag to clean the camshaft and the mounting surface of the sprocket. Camshaft endplay is a very important aspect of our conversion from flat tappet to roller.
There are a couple types of camshaft thrust buttons, and we chose the nylon style (part number 202). The steel roller bearing style buttons use shims to space out to the appropriate endplay, while the nylon button is a file-fit unit. We sanded a little at a time to keep from taking away too much material.
After we feel like it’s pretty close, it’s time to install the camshaft sprocket with the button in place. Then, we install the outer plate on the timing chain cover with no gasket or sealant. We tighten all of the countersunk allen head bolts.
Using a long screwdriver, we carefully pry against the camshaft lobes to move the camshaft forward and backward. If the camshaft does not move, you should remove more material from the nylon button. COMP Cams suggests setting the endplay between .005- and .010-inch, using a dial indicator to measure front to back movement of the camshaft.
After the endplay checks out within COMP Cam’s spec, we remove the outer timing chain cover plate, and then prepare to install the timing chain. We are installing the camshaft “straight up” meaning that we are using the “0” on the crankshaft sprocket, and lining it up with the dot on the camshaft sprocket.
Now is the time to break out the red Loctite for the three camshaft sprocket bolts. This is the only time you should need Loctite thread locker during the roller conversion process.
We torque the three camshaft sprocket bolts to 25 lb-ft and double check that our dots are still lined up and there is no binding in the chain.
A thin layer of high temp RTV silicone is applied to the outer timing chain cover plate before final assembly.
The 10 countersunk allen-head bolts can be installed for the last time. Don’t forget to install the flat plug in the center of the cover, which is the access hole for the dial indicator while checking camshaft endplay.
Two pointers are included with the timing chain cover kit—one for a small balancer and one for a large balancer. Choose the appropriate pointer for your application and install it using the two supplied bolts.
Also supplied in the timing chain cover kit are low profile bolts, which are necessary for proper clearance between the timing chain cover and a short water pump. We remove the standard hex-head bolts and replace them one at a time with the new hardware to offer a little more clearance.
The COMP Cams 853-16 retro-fit hydraulic roller lifters are the key to this conversion, as they offer a link-bar design to slide directly in place of the original drop in flat tappet lifters.
After applying installation lube on the rollers, we dropped the lifters into the bores. Take note that the link bars are pointed toward the lifter valley, and not toward the block.
When switching from a flat tappet camshaft to a roller, it is important to change the fuel pump pushrod to a bronze-tip unit, like this 4607 pushrod from COMP. Any COMP Cams camshaft with a part number that ends in “-8” or higher requires a bronze-tip or roller tip fuel pump pushrod because of the billet steel construction.
The new fuel pump pushrod goes into place with the bronze tip facing the camshaft. Then, the fuel pump backing plate can be installed, and finally, the fuel pump is bolted into place.
While the engine was apart, we sent the Dart Pro1 200cc cylinder heads to Farrow Motorsports in Chattanooga, Tennessee to be checked out. They needed a little shave to be perfectly flat, but were otherwise good to go.
COMP Cams 986-16 dual valve springs were part of the cam kit, and feature a 1.430-inch outside diameter and .697-inch inside diameter. With a spring rate of 322 lb-in. these springs are good for .540-inch lift.
Farrow Motorsports installed the new dual valve springs, using new seals, locks and retainers with the COMP kit.
It’s always a good idea to chase the threads of the cylinder head bolt holes. This ensures proper torque specifications, which can prevent sealing problems down the road. Use penetrating oil to lube the thread chaser.
New Fel-Pro 1003 head gaskets are placed on the block, in preparation for re-assembly. Now is the time to inspect all of the cylinders to make sure there isn’t any debris or foreign objects on top of the pistons.
We drop the Dart heads onto the dowel pins and start threading the ARP bolts into place after treating them to a dose of ARP Ultra-Torque assembly lubricant.
This ensures proper torque specifications.
Starting in the center and working our way out in a clockwise pattern, we tighten the head bolts, in three steps, finally reaching 70 lb-ft. We double check our work and move onto the other side.
We chase the threads, clean the bolts, install the gaskets and set the other cylinder head into place. Then, it’s time to go through the torque sequence again to ensure proper sealing.
Headers are next on the list, so we slide them into place and install the new gaskets and our existing hardware. Kyle Shadden helped us clean up the headers before we gave them a fresh coat of high temp paint.
Included in the K12-432-8 kit are High Energy 7809 pushrods, which are 7.266-inches in length and 5/16-inch in diameter. The rocker arms are COMP Cams 1601 Ultra Pro Magnum units, featuring a 1.52:1 ratio and 3/8-inch stud fitment.
Although the 7.266-inch pushrods are a standard size for retro-fit hydraulic roller setups, it is important to measure for proper pushrod length. Step one is to coat the ends with COMP valve train assembly spray, before we check the pushrod length.
Using a Sharpie, we color the valve stem before installing the pushrod and rocker arm. Many factors go into determining correct pushrod length, including deck height, rocker arm ratio, head gasket thickness and more.
Now, the rocker arm can be installed and adjusted. Although COMP Cams lifters do not require pre-soaking, we would advise soaking the two lifters that you plan to use for pushrod length checking. This will ensure they are pumped up to provide accurate results.
We rotated the engine by hand two full rotations, and then removed the rocker arm to see the wear pattern on the valve stem. The wear pattern is perfectly centered on the stem, so our pushrod length is dead on. Too short or too long of a pushrod will provide an off-center wear pattern, which puts a side load on the valve.
Once we’ve determined that the 7809 pushrods are correct, we can spray the valve stems, valve springs and pushrod tips with assembly spray.
We slide all of the pushrods in place and start setting valve lash before we install the intake manifold. This offers a lot more visibility to make sure the pushrod is properly seated in the lifter.
Setting valve lash involves rotating the engine by hand, to position the lifter on the base circle of the camshaft. To do so, adjust the intake valve when the exhaust valve just starting to open. Then, adjust the exhaust valve once the intake valve is nearly closed.
Tighten the rocker arm nut until you can feel resistance in the pushrod. This point is known as “zero lash”. COMP Cams suggest one-half turn of preload on the 853 lifters. That means after you reach zero lash, turn the rocker arm nut one-half turn and then tighten the lock with an allen wrench. Repeat this process for all eight cylinders.
The intake manifold can now be re-installed using new Fel-Pro gaskets. After the intake is bolted into place, it would be a good time to prime the oiling system, if you so desire. It isn’t absolutely necessary, but it doesn’t hurt.
Another very important note regarding a switch from flat tappet to roller is the distributor gear. A standard cast iron gear will wear out the camshaft, which is certainly not what you want. COMP Cams offers three suggestions for proper distributor gears—composite, melonized steel or bronze. We chose the COMP Cams 12200 Composite gear for this project.
The HEI-style distributor is dropped into place, with the rotor pointed toward the number one cylinder while the engine is on top dead center. Any time a new camshaft is installed, it’s important to get the timing right on the first shot, as the first few moments of run-time are the most crucial.
We finished off the freshened small block with a new set of COMP Cams cast aluminum valve covers. The tall design offers plenty of clearance for our roller rocker arms, and the black wrinkle finish is easy to clean.
COMP Cams 10W-30 Break In Oil is used to fill the oil filter, and then we added five quarts to the empty small block. The break-in process is important with any new roller camshaft setup, but it’s not nearly as crucial as flat tappet camshaft break-in. We brought up the RPM to around 2,000-2,500 as soon as the engine came to life, in order to get plenty of oil flowing.
After breaking in the new components, it was time to change the oil, and inspect the engine for leaks and any problems. Then, we put a couple hundred miles on the engine, changed the oil again and we were able to get out and enjoy our new combination. The new camshaft setup offers a great exhaust note, and it moved the power band to a more usable area for the car.
