Originally developed in 1955 at 265 cubic inches, the small block Chevy engine has evolved into the most popular engine in history. With literally millions of factory production units in circulation, the performance aftermarket has exploded with countless variations of this engine. When choosing a piston, the choices can be reduced to a few simple steps.

Piston to cylinder head compatibility is determined by two major factors, dome shape/size and valve relief (VR) placement. VR placement on the piston is influenced by two characteristics of the particular cylinder head being used; valve angle and valve spacing. The following paragraph discusses the VR placement characteristics of the most popular small block Chevy cylinder head, the 23º.

Factory GM heads are used to define standard valve spacing and angle (thus 23º) for many small block Chevy’s. Additionally most 23º aftermarket cylinder heads incorporate what is commonly known as "60/40 Shift" (See diagram at right) in order to allow for larger valves. All JE flat top and inverted dome shelf piston designs accommodate "60/40 Shift" and will work with most aftermarket 23º cylinder heads, including those with oversized valves and angle milled surfaces. TFS "Twisted Wedge", AFR227 and Brodix 10X cylinder heads will require custom pistons.

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JE domed pistons share the same compatibility as the flat top and inverted dome pistons. Only the Pro Action/ Pro Topline, Brodix 11X, GB2000, GM Vortec and the GM Fast Burn heads require special pistons in addition to those mentioned above. In some cases, as in the Pro Topline Lightning 23º, JE has designed specific shelf parts to suit these applications.

Although the 23º head is by far the most popular, the performance aftermarket industry has developed several variations that employ different valve angles and VR placements. These styles include cylinder heads such as the Brodix –12 15º, 17º/18º... etc. and have specific sections in our catalog dedicated to them. These special application shelf pistons will work with nearly any aftermarket head of the same valve angle style.

REMEMBER, always check piston to cylinder head clearance during assembly as shown in the diagram below. If you have questions regarding the VR placement on your particular cylinder head, JE suggests that you contact the cylinder head manufacturer directly.

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