COMP Cams Camshaft Installation and Degreeing Procedure - Manual (Page 7)

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COMP Cams®
3406 Democrat Rd.
Memphis, TN 38118
Phone: (901) 795-2400 Fax: (901) 366-1807
www.compcams.com
Part #145
Revised 5/4/12
Valve Springs
The number one factor in premature failure of a new camshaft is an improper or worn-out valve spring.
Either incorrect pressure or incorrect spring application will lead to a worn-out camshaft. For this
reason, it is highly recommended that the corresponding part number COMP Cams spring be used
with any cam change. Most aftermarket cams have much higher than stock lift. Therefore the stock
valve springs will “coil bind” or “stack” before the cam reaches its full lift. This condition will cause
the cam to fail immediately. With the valve at full lift, check the clearance between the coils. A
minimum of .060” between the coils needs to be maintained.
When assembling the head, check the retainer to valve seal clearance. Sometimes when installing a
high lift cam and a different seal, this distance becomes too small. This will bind the valve train and
result in camshaft failure. If the clearance does not measure the total valve lift plus .060”, the heads
should go to the machine shop and the guides shortened. Excessive spring pressures will also lead to
early cam failure. The only way to ensure the correct pressure is to actually check the installed height
and have the springs tested. Refer to the specifications on the valve spring box or contact COMP
Cams® at 1-800-999-0853.
Piston to Valve Clearance
COMP Cams strongly urges you to check the piston to valve clearance on the larger street cams and
all race cams. The easiest and most accurate way to check this is to place strips of modeling clay on
top of one piston, then rotate the engine over by hand with the cylinder head bolted in place and all of
the valve train adjusted. If there is any resistance during rotation of the crankshaft, STOP! The piston
has probably hit the valve. Then you must decide whether to flycut the piston, or exchange the cam for
a profile that will fit into your engine. Note: Minimum piston to valve clearance is .100” on the
intake and .125” on the exhaust valves. If aluminum connecting rods are being used, add a
minimum of .030” to these suggested clearance figures. Aluminum rods will stretch and expand
more than steel rods.
Checking Piston to Valve Clearance
Note: Be sure to check piston to valve clearance after the cam has been degreed. The positioning
of the cam in the engine will greatly affect the piston to valve clearance.
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.
2. Apply a strip of model clay 3/8” to ½” wide approximately ¼” thick to the pistons. The clay
strips should be placed perpendicular (across) to the intake and exhaust valve reliefs. Applying
a small amount of oil to the clay will prevent it from sticking to the valves as they press into it.
3. Reinstall the cylinder head with the head gasket that is going to be used. It will not be
necessary to retorque 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