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BIG BLOCK CHRYSLER - TECH HIGHLIGHTS

BIG BLOCK CHRYSLER - TECH HIGHLIGHTS
 

The big block engine from Chrysler was offered in two basic styles, the B designated engines having a shorter deck height than did the RB types. In the former group are the 383" and 400"; the 426" and 440" are in the latter. Most external engine parts, cylinder heads, and valvetrain related components are interchangeable between the two groups. While the 426" engines, whether Hemi or Wedge, are scarce collector's items today, the others are readily available and make excellent street or race packages when properly prepared. The 440" is easily the best engine to use for performance, in this case bigger really is better.


One key determining factor in piston selection will be the cylinder head chosen. Contrary to previously published data, only two cylinder head configurations are commonly used within this engine family. The closed chamber heads, with a volume of approximately 78.5c.c., were used in 1967 and earlier vehicles. The most desirable of these were from the 1967 440HP. These feature larger exhaust valves and carry a 915 designation. The open chamber heads average around 88c.c., and are found on all 1968 and later applications. The preferred version of this design was found on 1968-70 engines. Identified as the 906 castings, these heads have a better port configuration than do the later emission heads. The old information that indicated a wider variety of chamber volumes for these engines was based upon reported minimums, established for the use of certain race sanctioning bodies. These were intended to give the Chrysler racer a competitive edge in tightly controlled racing classifications and events.


The compression ratios in the Federal-Mogul catalog have been recalculated to reflect real world data, using a single reference head gasket of .0375 in thickness. Deck clearances are calculated from the standard, uncut factory block deck height. The pistons have not been changed! All that has changed is the use of a more realistic approach in stating the compression ratio. Many original muscle car engines never actually had the high compression ratios which they were credited with. Cylinder heads vary from specifications widely, checking their true volume and measuring actual deck clearance is the only way to accurately determine your compression ratio. Since many Chrysler engines use large deck clearances, it is possible to mill the block to raise compression.


One other area requiring special attention when building a 440 is in the balancing method used by the factory. While most of the engines are internally balanced, the versions using the six pack rods (P/N 2951908) or a cast crankshaft (1975-78) are externally balanced. And require a specific balancer and flywheel. This is also true of the 1970-71 383 2bbl. And the 1972-78 400 engines. Camshafts for the big block Chryslers used one of two timing gear retention methods; either the single bolt type and the three bolt type. The latter is preferred for most high performance applications. When using roller or solid lifter cams an adjustable valvetrain is necessary. This conversion will require both the rocker arms and a set of matching pushrods. You must have an additional .060 of valve spring travel available at maximum cam lift, and maintain a minimum of .100 piston to valve clearance.



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