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How To Swap An LS Cam

The GM LS is one of the most affordable and versatile engines on the market today. COMP Cams has enthusiastically responded to this popularity with a wide variety of high performance camshafts and upgrading to one couldn’t be easier. To demonstrate this, Xceleration Media’s Richard Holdener recently hosted a step-by-step video on swapping a more potent COMP grind camshaft into a stock LS3 crate engine. (See video here or below). Below is an overview of Holdener’s information for those who like to read.

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It’s a good idea to replace factory pushrods with hardened versions, especially if your new cam is going to increase spring pressure.

The first step in performing an LS cam swap is to remove the valve cover, coil pack and spark plugs on the driver’s side of the engine. With the valve cover off you now have access to the rocker arms. Unbolt all of the rockers and the rocker assembly will come off as one piece. Before you do that though, check to see if any rockers have spring load. If so, undo all of the other unsprung rockers, rotate the engine to relieve the loaded rockers and unbolt.

The final step is to remove the pushrods. If you are working on a factory engine that utilizes non-hardened pushrods, it’s a good idea to replace them with COMP Cams hardened versions, especially if your new cam increases valve spring pressure. Once you’ve repeated this process on the passenger side, it’s time to head to the front of the engine.

For a crate engine that has just been unboxed, camshaft access is easily gained with the removal of the water pump, damper and front cover. If the engine is in a vehicle it will also be necessary to remove the radiator, radiator hoses and heater hoses.

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Once the front cover is removed, rotate the engine to align the timing marks at Top Dead Center.

Remove the six 10mm bolts of the water pump. If your engine has more than 50,000 miles it’s a good idea to replace the gaskets. With the water pump off it’s time to remove the damper. You can use a special pulling tool with a three-arm design that will engage with the three indentations on the damper’s backside. Once the tool is in place, simply tighten the bolt and the damper will slide off.

The final obstacle in accessing the cam is the front cover. Once it’s removed you’ll want to rotate the engine to push all of the lifters out of the way and up into the trays, and to align the timing marks at Top Dead Center. Top Dead Center is the correct position to install the camshaft and is achieved by rotating the engine until the upper and lower timing marks line up. You are now ready to do the cam swap.

If your engine has a chain tensioner, be sure to relieve the tension before removing the cam bolts by installing a tension pin. With the timing sprocket unbolted and out of the way you’ll now have access to the cam retaining plate and the four bolts required to remove it. Once the cam retaining plate is removed, spin the cam a few more rotations to make sure the lifters are all up in the trays.

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Do not install a new camshaft without first cleaning and oiling it.

Be very careful taking the cam out. You don’t want to damage any of the lobes or bearings.  Next, make sure to put plenty of fresh oil on the new camshaft before installing it. DO NOT install the camshaft without cleaning and oiling it first. Slide it in nice and easy until it fits snugly in the block. Reinstall the cam retaining plate and torque the bolts to the factory settings – 18 ft./lbs. on an LS3 like ours.

With the cam retaining plate in place it’s time to install the cam sprocket. Remember that this sprocket might need to be replaced when installing an aftermarket cam. For instance, the factory cam for our LS3 would’ve come with a single-bolt 4x cam sprocket. Our aftermarket cam is a stronger three-bolt design, so a new three-bolt 4x cam sprocket has to be used. It’s imperative to use the right sprocket.

One trick to make sure the cam is in the right place before the cam sprocket is installed is to put only one
bolt in the sprocket and spin it so the timing marks on the upper and lower sprockets are lined up. Then you can put the chain on. With all the bolts in place torque them to 26 ft./lbs. and you are ready to pull the pin from the tensioner.

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Be sure to use the right cam sprocket based on your new camshaft’s design.

Once the cam sprocket is installed, it’s time to install the front timing cover. Be sure to put it on “finger tight” to begin with, as you won’t fully tighten the front cover bolts until the damper is on. According to the factory procedure, GM recommends tightening the damper to 250 ft./lbs. to make sure it’s seated properly. Then back the factory bolt off  and discard. Replace it with a new bolt, torque to 37 ft./lbs. and then rotate your wrench an additional 140 degrees.

With the damper snugged into place it’s time for reassembly. Tighten the front cover bolts and add the pushrods. The rocker arms go back on as one assembly and you’ll want to tighten them lightly to start with. Next, torque any rockers that don’t have spring pressure on them to 22 ft./lbs. Then rotate the engine to relieve the spring pressure from the other rockers and torque them down to 22 ft./lbs. as well. Do this for both sides and finish by reinstalling the valve covers, coil packs and spark plugs.

A cam swap alone can be worth up to 60 horsepower – meaning that one of the most basic elements of engine building can pay big dividends, and as you can see, it’s pretty easy to do.