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COMP Cams®
3406 Democrat Rd.
Memphis, TN 38118
Phone: (901) 795-2400 Fax: (901) 366-1807
www.compcams.com
Part #117
Revised 4/17/12
Gear Drive System Part #4100, #4110 and #4136
Thank you for choosing COMP Cams® products; we are proud to be your manufacturer of choice.
Please read this instruction sheet carefully before beginning installation, and also take a moment to
review the included limited warranty information.
Notes:
1. The installation procedures which follow assume that the engine has been disassembled and
cleaned as it would be for a normal timing set change.
2. The reverse idler gear should have between .005 and .070 in vertical travel when the set is
installed on the engine with the power idler in hard mesh between the crank and cam gears. If
this is not the case excessive, heat can be generated causing damage to the gear set.
3. The purpose of the reverse idler gear is to prevent the power idler from disengaging when the
crankshaft rotates backwards as happens in shutting off the engine.
4. The engine is timed with the timing marks facing one another just as you would with a chain
and sprocket drive.
5. If a factory timing cover is not used some minor machining to the timing cover may be needed
for use with this set.
6. Idler pins will always be in contact with the timing cover during use. Back of idler pins must
have a minimum of .015 clearance to block.
7. The Dual Idler Gear Drive is intended for use with a harmonic balancer. It is not for use with
an aluminum hub.
Installation Instructions:
1. First, place the bronze wear ring on the counterbore side of the camshaft gear. A small
amount of grease will keep the ring in place during installation of cam gear.
2. Install the camshaft gear on the camshaft and torque to factory specs.
3. Install the crankshaft gear on the crankshaft using the desired keyway. The rounded
keyway is for standard camshaft timing. The triangle shaped keyway is for 4-degree
camshaft advance while the flat topped keyway is for 4-degree camshaft retard.
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COMP Cams®
3406 Democrat Rd.
Memphis, TN 38118
Phone: (901) 795-2400 Fax: (901) 366-1807
www.compcams.com
Part #117
Revised 4/17/12
4. Align the timing marks as shown in the figure below.
5. Install the idler bracket in place. (It may be necessary to rotate the engine slightly to align
the gears).
6. After idler bracket is in place, turn the crankshaft forward slightly to place the power idler
in hard mesh. The reverse idler must have between .005 to .070 in vertical travel.
7. Pull the idler gears halfway out of mesh with the crank gear. With timing cover gasket in
place take timing cover and push into place. Remove timing cover and that is where the
idler bracket will run. If the front of the idler gears do not line up with the front of the
crankshaft gears, machining of the timing cover is required.
8. After the idler gear alignment has been completed; check the clearance between the idler
pins and the block. There should be between .015 and .060 in clearance. Remove the idler
bracket and grind off end of idler pin if necessary to achieve the required clearance.
9. Replace the idler bracket, install the cam button and install the timing cover.