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The small block Chrysler has been in continuous production for about thirty years, and is found in several displacements, The 273" was used in some performance packages in the mid-sixties, but is rarely found today. The more popular 318", 340", and 360" are the engines covered in this catalog. The 318" is suitable for mild performance usage, but potential is limited in comparison to the other two. The 340" was the high performance small block engine in Chryslers muscle carsĀ, many race oriented performance upgrades for the small block Chrysler were developed for this particular engine. The 360" is more readily available than the 340", offers better potential than the 318", and is recommended for most street performance applications.

When choosing pistons for these engines, pay particular attention to cylinder head selection. There are a wide variety of heads available, and these will dictate which piston to use. Most of the pistons offered are flat tops that use various compression distances to deliver a desired compression ratio when used with a particular cylinder head. The high compression 340" engines often have positive deck heights, with the pistons protruding about .018 out of the block. This condition mandates careful inspection of piston to head and piston to valve clearances, and requires that "decking" of the block be held to a minimum. For 360 engines, our new H116P is a fully CNC machined hypereutectic piston that delivers a deck clearance of .015 and a compression ratio between 9.5 and 10.0 to 1. In comparison, many other engine combinations possible within this group place the piston fairly low in the cylinder, and respond well to deck machining for increased compression.

The compression ratios listed in this catalog are referenced to a single head gasket thickness of .039. and to an uncut factory block's deck height. The pistons have not been changed, but the variables have been eliminated, thus the ratios shown may differ from those previously published. The resulting ratios, whether for Hypereutectic or Powerforged pistons, can be directly compared to one another. The cylinder head volumes we used are also for reference only, as the chamber volume of factory heads will vary by 3 or 4 cc's from specifications in most cases. Unless you measure both actual deck clearance and chamber volume, you cannot accurately determine the compression ratio.

The 318 is rather easy to "overcam", be conservative when selecting a cam for one of these engines. An adjustable valvetrain is available for this family, and is required when using roller or solid lifters, as well as with the CS1225R hydraulic lifter cam which has a small base circle design. Pay particular attention to valve spring installed height, which is rather short in these applications, and to the potential coil bind conditions which can occur. There must be at least .060 of additional spring travel available at maximum valve lift. Also be cautious when installing the rocker arm assemblies, as the rocker arms are not identical and must be installed in the correct position. Rocker shafts must be assembled with oiling holes facing downward to ensure proper lubrication.

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