COMP Cams Chrysler Engine Technical Specs and Information

CHRYSLER TECHNICAL INFORMATION Engine Types \| General Tips
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. Finally, there is the ever present CAM HELP® line at 1-800-999-0853.
Engine Types
Small Block, "A" Uses "20" Prefix The basic 273-360 engines, produced in the mid 1960’s, have remained relatively unchanged as far as the valve train is concerned. The 1964-1991 engines used shaft type rocker arms, which required some special changes in the camshaft design. This was to allow oil to flow to the top of the engine and into the rocker arm shafts. Most of these early engines featured either grooved or offset holes in the second and fourth cam journals. In some instances a combination of both grooves and holes were employed. You must remember that if your engine has shaft type rocker arms, there must be some groove or oiling hole combination on the cam journals. In 1992 the Magnum version of the “A” engine was changed to a pedestal style individual rocker arm design. Move to Top Magnum The new Magnum engines utilize a pedestal mount rocker arm system. They come from the factory with a nonadjustable valve train and have 5/16” bolts fastening the rockers to pedestals on the heads. Move to Top 5.7L & 6.1L Hemi, Uses “112” Prefix In 2003 Chrysler called on the legendary “Hemi” cylinder head design to begin a new era in Mopar performance. This new engine has the same familiar perpendicular valve arrangement but does not share any parts with the classic Hemi engines. Rocker arms are shaft mounted with 1.6 ratio on intake and exhaust. Two rocker shafts per head are used, which is similar to the earlier Hemi. Because of this design, different length intake and exhaust pushrods are used. The new engine also uses smaller, .842” diameter hydraulic roller lifters and a single bolt cam sprocket. 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. Move to Top V10, Uses “97” and “111” Prefixes (Viper) We have two different cores for this engine, depending on the year model. The 2002 and older blocks use a single bolt core, and the 2003 and later cores are a 3-bolt design. Big Block “B” or “RB”, Uses “21” and “23” Prefixes The “B” and “RB” engines used two different deck height blocks. They require different length pushrods, so when considering pushrod length, remember that the 383-400 engines use a shorter pushrod than the 413-440 engines. The larger engines with the taller blocks use a pushrod that is approximately 3/4” longer than the other. 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. Move to Top Hemi, Uses “24” and “26” Prefixes There are two basic factory versions of the original Hemi engine. The most common is the 426 Hemi, which was introduced in 1964. It uses the “24” prefix. Derivatives of this engine can be found in almost all Alcohol and Fuel cars racing today. One of the most popular drag racing engines, it is easily recognized by the distributor location, which is in the front of the block. As far as production engines are concerned, most of the parts are interchangeable. Hybrid Hemis; however, have relatively few interchangeable parts because most are custom made. 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. Move to Top

General Tips

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.

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