High Lift Cams
When changing to a higher than stock lift cam, several items must be checked to ensure long engine life and high performance. Spring coil bind, correct pressures, retainer to guide clearance and piston to valve clearance are just a few of the more common considerations. There is no exact formula to tell when you are getting into trouble, so to avoid serious problems, it is better to double check these things when installing a cam. If ever unsure, contact CAM HELP® at 1-800-999-0853.
By far the most common problem encountered when installing a new high performance camshaft is the incompatibility of the existing valve springs to the new cam. Factory valve springs are designed to work with a certain lift cam, and since most aftermarket cams have higher lift, the springs must be addressed. It is highly recommended and a requirement of the warranty that the suggested springs be installed along with any COMP Cams® camshaft.
Valve Stem Oil Seals
When changing to a higher than stock lift camshaft, it is common to have a clearance problem between the bottom of the spring retainer and the top of the valve stem oil seal. Before final assembly of the heads, install one seal, one valve and one retainer without the spring. Measure the distance between the top of the seal and the bottom of the retainer to be sure that it is greater than the lift of the valve by at least .050”-.060”. Be sure to take into account any extra lift due to higher ratio rocker arms.
Flat Tappet Break-In
All flat tappet cams require special attention during the break-in process. Special springs and certainly tender loving care will be required to ensure long life of the cam. Please refer to the instructions in your cam box for complete procedures. If ever in doubt, please call the COMP Cams® CAM HELP® line at 1-800-999-0853.
High Ratio Rocker Arms
A higher than standard ratio rocker arm moves the pushrod closer to the rocker arm shaft. 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 when 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 and shaft height. Usually, a longer than stock pushrod will be necessary in a high performance engine, but care must be taken to choose the correct length.
Fuel Pump Pushrod
All Chrysler “B”, “RB” and Hemi engines use a fuel pump pushrod to actuate the fuel pump. The fuel pump must be removed and the rod dropped away from the cam prior to camshaft removal. Failure to do so will result in damage to the cam, pushrod or both.
Rocker Arm Adjustment/Lifter Preload
All but a few Chrysler engines were equipped at the factory with non-adjustable rocker arms. Anytime a solid lifter camshaft (either roller or flat tappet) is used, you must also use the adjustable rocker arms and appropriate pushrods.
When installing any high performance hydraulic camshaft, the lifter preload is something which must be considered. Too little preload will result in a noisy valve train, and too much preload will result in tight valves and a poor running engine. Either condition can result in less than expected performance or engine failure. After the cam, lifters and rocker arms are installed and prior to installing the intake manifold, you must check the plunger depression in the lifter. With the cam on the base circle (valve closed) the plunger in the lifter should be depressed .040”-.060”. With nonadjustable rocker arms, you must change pushrod lengths to obtain proper lifter preload. This is a delicate and time consuming process, so if you have any questions, contact the CAM HELP® line at 1-800-999-0853.
Rocker Arm Shafts
When installing the rocker arms on a shaft type system of a Chrysler engine, the shafts must be installed correctly. There is a difference in the top and the bottom, as well as side to side. The shafts must be installed with the oil holes pointed to the bottom and to the outside of the engine, toward the valve. This is the only way the shafts can adequately oil the rocker arms. Premature wear will result if the shafts are installed improperly.
The pushrod seat location is different in hydraulic and solid lifters in most applications. For this reason, pushrod length must be checked and may need to be changed when switching from solid to hydraulic camshafts.
When installing a roller cam and tappets into a Chrysler engine, you must be careful to ensure that the roller lifter sits in the lifter bore correctly. Most brands of roller lifters are designed with a cut-out in the lifter body around the lifter wheel. If this is installed toward the oil galley in the block, the result will be a loss of oil pressure and engine damage. COMP Cams® roller lifters do not incorporate this cut out, so there is no problem when using COMP Cams® lifters. When installing roller lifters in the block, remember to install the link bar side of the lifters to the cylinder side in small blocks and to the inside in big blocks and Hemis.
COMP Cams® produces a special lifter for oval track use in the “A” engines. This lifter is still the standard .904” diameter but is made to oil through the pushrod. This is for use in special highly modified blocks only and will not work in a standard block.
There are several different roller lifters listed for the Hemi engines. The only difference is the location of the pushrod seat.We have basically developed a drop-in replacement for most of the popular brand lifters available. Be sure to measure the height of the pushrod seat prior to ordering lifters.
Lifter Bore/Oiling Modifications
Even though COMP Cams® roller lifters will work without oil system or lifter bore modifications, it is highly recommended that on any racing engine the lifter bores be modified. This will ensure that in the case of a pushrod failure and the lifter coming out of the bore, adequate oil pressure will be maintained. The proper procedure for this modification can be found in any of the materials available directly from Chrysler, or any top engine builder can perform this modification.
Camshaft Journal Diameter
Many of the newer 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. It is very common to use a 2.125” Ford babbit bearing in the Hemi engine. Some of the latest oval track blocks feature a roller bearing and require a 1.968” journal diameter. Make sure to specify journal size when ordering your cam. If no special size is requested, the standard journal will be chosen.
Camshaft Cores/Timing Chains
On the big block “B” and “RB” engines there are two designs of the cam snout/upper timing sprocket where the cam is attached to the gear. The most common design is the single bolt type, which just means that the cam is attached to the timing chain with a single bolt. There is also the 3-bolt type, more common in high performance applications. These designs are totally inter-changeable, as long as the proper cam is used with the correct timing chain set. In any case, the 3-bolt design is the only style available for roller camshaft applications.
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® machined steel 10º Super Locks™ and the variety of spring retainers available with this lock. Super Locks™ are now available for the multi groove Chrysler valves in both the 2 and 4 groove applications. They are available in pairs or in a kit with half 2 groove and half 4 groove locks. See page 311 for details.
Lifter Bank Angles
The latest version of the “A” engine block features a different lifter bore angle. This block is commonly called the “R” block. The angle of the lifter bore is changed to help straighten out the pushrod angle. The standard lifter angle on the “A” engine is 57 degrees from vertical. This points the lifter away from the center of the block and angles the pushrod toward the outside. Most of the “R” blocks and some highly modified versions of the “A” engine have a 48 degree lifter angle. This points the lifter more directly at the rocker arm and helps to eliminate deflection at very high engine speeds. No standard production blocks were made with this modification, so if your block is not a special “race only” part from Chrysler, you probably have the 57 degree lifter angles. These cams are not interchangeable, so it is important to note the lifter bank angle prior to ordering any racing cam. If no special lifter bank angle is stated, the standard 57 degree cam will be used.
The same changes are common on some of the newer aluminum aftermarket Hemi blocks, the difference being much more subtle, from 45 to 48 degrees. It is extremely important to make sure which lifter angle your block is machined for prior to ordering a cam. As with the small block, if no special lifter angle is requested the cam will be ground as with the standard 45 degree lifter angle.
COMP Cams® has invested millions of dollars in Research and Development in order to stay years ahead of our competition. With today’s technology and brilliant minds working around the clock, COMP Cams® has rightfully earned respect as the leader in valve train technology in the automotive industry. Quality control is our main objective in creating award winning components, and the ADCOLE Model 911 is just one of the many machines we have invested in to maintain that quality. When you purchase any COMP Cams® valve train components, you make an investment into tomorrow’s leading edge technology in pursuit of ultimate power.