|Chrysler, one of the most dominant names during the early “Muscle Car” era, has developed five basic series of engines which are popular choices in racing, street performance and towing applications. For our purposes we will refer to the 273-360 Small Block Chrysler engines as the “A” engine and the 383-440 big block standard head engines as the “B” engine. In recent years, the engineers at Chrysler have introduced three versions of the V10 engine platform, as well as a new 5.7L & 6.1L Hemi design. In the following information we have attempted to pass along some common “tips” learned during our many years of engine building, as well as the experiences of many of our customers. We will not attempt to cover all of the little things, only the more unique and aggravating trouble spots. If ever in doubt, there are many excellent reference manuals. Mopar Performance has one of the best. It goes into great detail about Chrysler engines. If you need more help or have any questions, please call our CAM HELP® line at 1-800-999-0853.
Small Block, "A" Uses "20" Prefix
5.7L & 6.1L Hemi, Uses “112” Prefix
There are concerns when installing aftermarket camshafts in these engines. The factory piston has a dome and no valve reliefs. Extra caution should be taken to ensure adequate piston to valve clearance. It is also necessary to deactivate the MDS (multiple displacement system) when installing and using a performance camshaft. Computer tuning must be performed to enhance drivability.
V10, Uses “97” and “111” Prefixes (Viper)
When converting either of these engines to adjustable rocker arms, you must also replace the pushrods. The standard pushrod used with nonadjustable rocker arms uses a pushrod with a ball on each end. COMP Cams® aluminum roller rocker arms use a pushrod with a ball on the lifter end and a cup on the rocker arm end. The new COMP Cams® Pro Magnum Rocker Arm™ Kit for these engines uses a ball-ball pushrod like the standard setup, but the length is different. In either case, the correct pushrods must be used for the rocker arm type selected.
Hemi, Uses “24” and “26” Prefixes
The old style 301-392 Hemi engine, which uses the “26” prefix, is most readily recognized by the location of the distributor at the rear of the block. There were several versions of this engine; therefore, it is highly recommended that before ordering any parts you make sure exactly which engine you are working on. These engines were very popular in the 60’s and 70’s and can still be found in many street machines and street rods, but they are becoming very hard to maintain due to the lack of replacement parts.
High Lift Cams
Valve Stem Oil Seals
Flat Tappet Break-In
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
Fuel Pump Pushrod
Rocker Arm Adjustment/Lifter Preload
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 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
Camshaft Journal Diameter
Camshaft Cores/Timing Chains
Multi Groove Valves
Lifter Bank Angles
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.