Quote:
Originally Posted by i82much
i thought most forged pistons were either 2618 or 4032, with 4032 allowing tighter clearances. is there something else that J&E uses? any reason why a 4032 from another outfit wouldn’t have the same clearance requirements as J&E?
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There are some other factors that play into the manufacturer's piston to wall recommendations. Alloy is a major factor. Also the amount of cam shape ground into the skirts, the size and style of the expansion holes, the position of the ring pack and the ring dimensions. Finally, the length and contact area of the skirts. The BME web site has a lengthy discussion of the advantages and disadvantages of 2618 vs 4032 alloy. Bill Miller has a engineering degree with specialties in metallurgy, so I am confident in his views. The Readers Digest version is 2618 is more ductile and crack resistant, far superior in drastic pressure rise applications or detonation prone environments. Such as blown, high loads of nitrous and other very high HP applications. It does require more clearance than 4032. 4032 is a nice option for performance street, and mid-level racing applications. Quiet and easy on cylinder walls. In our Pontiac engines I read this as about 700-800 HP NA engines. Over that, or with a big power adder, I would tend to move into the 2618 alloy. FWIW.