COMP Cams 4120 Gear Drive System - Manual (Page 2)

COMP Cams®
3406 Democrat Rd.
Memphis, TN 38118
Phone: (901) 795-2400 Fax: (901) 366-1807
www.compcams.com
Part #118
Revised 5/31/13
3. Install crank gear on engine. You can advance or retard the camshaft timing ±2 cam degrees
from factory setting by using the advanced keyway (triangle keyway and timing mark) or the
retarded keyway (rectangle keyway and timing mark).
4.
With the #1 piston at TDC line up timing marks on engine centerline as shown in the figure
below, slide idler gears in place with large gear on the passenger side of engine. On 351W and
late model 302 engines the long pin in the idler assembly must be changed with the shorter pin
supplied in the set. On some 351M and 400M blocks most of long pin must be ground off to
allow proper clearance under the timing cover.
5.
With the idler gears halfway on push timing, cover with gasket into place. Remove the cover.
The gears should be aligned at least 90% with the cam and crank gear. Use a feeler gage to
check clearance between block and back of idler pins. A minimum of .015" to .060" is
required. If there is not sufficient clearance, remove the idler assembly and grind off material
from the end of the idler pin closest to the block. Repeat step 3 until correct clearance is
achieved.
6. With the idler assembly now in place, turn the crankshaft clockwise so that the power idler
(large gear) is in hard mesh with cam and crank gear. There must be .005"-.070" vertical travel
of the reverse idler (small gear). Replace the idler bracket, install the timing cover.