High Ratio Rocker Arms
A higher than standard ratio rocker arm moves the pushrod closer to
the rocker arm stud. It then becomes necessary to check the clearance
between the pushrod and the head where the pushrod passes through the
head. This is a very common problem and should be checked whenever a
rocker arm ratio change or pushrod diameter change is made.
Rocker Arm Geometry
Proper rocker arm geometry is necessary to ensure the maximum
benefit from any cam design. Camshaft base circle, block deck height,
cylinder head design and lifter design all contribute to possible errors in
geometry which must be compensated for with pushrod length. Usually a
longer than stock pushrod will be necessary in a high performance
engine, but care must be taken to choose the correct length. A
comprehensive explanation of the checking procedure can be found on
Multi Groove Valves
No longer is it necessary to convert to “Chevrolet” style single groove
valves to benefit from the superior strength of COMP Cams® Super Locks™
and the variety of spring retainers available with this lock. Super Locks™
are now available for the multi groove valves used in most 351C and
351M-400M applications. They are available in pairs or in sets and can be
found on page 311.
Hydraulic Roller Cams
In those engines originally equipped with hydraulic roller camshafts,
conventional flat tappet hydraulic and solid lifter cams can be used. It will
be necessary when making this change to use the corresponding cam,
lifters, pushrods, rocker arms, valve springs and timing chain set.
Retro-Fit Hydraulic Roller Cams
COMP Cams® has developed a special kit to allow the installation of
hydraulic roller cams in standard Ford V8 engines (289-351W, 351C, 351-
400M) not originally equipped with hydraulic roller cams. This kit uses
many of the same parts as the factory roller cam equipped 5.0 engines
use, including the lifter guides and retention tray. This kit can be used only
with specially designed COMP Cams® Retro-Fit Hydraulic Roller
Camshafts with special base circle size.
To ensure that you have the correct base circle size: install the cam,
lifters and all lifter retention hardware. Slowly rotate the camshaft, looking
closely at the top of the lifter where it contacts the guide bar. As the lifters
move up and down, the lifter guides should remain flat on the top of the lifter bores. The lifters must not push the guides up as the lifters rise, and
the lifters must not drop below the guide bar as they go all the way down.
If either of these conditions exist, the base circle of the camshaft is
incorrect and must be changed prior to complete installation.
COMP Cams® has developed new Pro Magnum™ hydraulic roller lifters
that will eliminate the need for the different base circles. This lifter, Part
#8931-16, is a captured link bar style lifter that is a simple drop-in design
for most Small Block Ford applications. We also offer a Big Block Ford
version, Part #8934-16.
Camshaft Retention Bolt
Most V8 Ford engines used a 3/8” bolt to secure the upper cam gear
to the cam. Almost all racing engines use a 7/16” bolt for this application.
Be sure to check the compatibility of the bolt to the cam, as a 3/8” bolt in
a 7/16” cam will almost certainly result in catastrophic engine failure.
Most of the COMP Cams® racing roller cams will come with the 7/16” hole
in the cam.
Camshaft Journal Diameter
Many of the newer all out racing engines utilize a larger than standard
cam bearing journal diameter. The advantages of the larger diameter are
less flex and a larger base circle to smooth out the lobe design, making
this a very desirable addition to any extreme racing engine. The most
common sizes other than stock are: 2.051” (babbit bearing, all 5 common
size journals), 2.081” (roller bearing, all 5 common size journals) and
2.165”/1.968” (roller bearing, commonly referred to as the “Large
Any of these sizes should be available, but none are interchangeable.
Make sure to specify journal size when ordering your cam. If no special
size is requested, the standard journal size will be chosen.