Page 317 of High Performance Parts for American V-Twins 2008 by S&S Cycle

1958-2008 50th ann iversary s&s® replacement pistons back in the 1950 s when s&s company founder george smith needed pistons for his race bike tramp he had to cast them himself the need for specialized pistons for high performance engines was a critical issue then and it is still so today improved designs and increased strength are required to make power and to hold up for the long run technology has made significant advances since those days and s&s has made use of improvements in metallurgy piston design and production techniques to provide specialized pistons for today s high performance applications while simultaneously improving engine life and dependability pictured all s&s piston kits come complete with rings wristpins and wristpin keepers important notes each of the many s&s stroker pistons are designed for a specific application by using these special pistons the stroke of an engine can often be increased without the use of base plates or special length cylinders since they generally have shorter piston skirts and a shorter deck height stroker pistons must be purchased separately when ordering a stroker kit and are available in standard oversizes as service replacement parts for stroker engines valve pocket recesses in s&s pistons are enlarged for oversize valves and higher lift cams all s&s pistons are sold in sets of two and come complete with rings wristpins and wristpin keepers piston rings are sold in complete sets for two pistons each forged piston alloy is optimized for the engine type and application high silicon content with lower expansion rates allows a tighter fit in the cylinder this results in less noise and longer piston life low silicon alloys provide greater strength but also higher expansion these pistons are best suited for high performance applications where strength is the most important consideration s&s oversized pistons for 1936 84 stock bore engines are based on standard bore for a 74 engine which is 3 7/16 3.4375 80 engines have a standard bore size of approximately 31/2 which is .060 larger than that of a 74 engine this can cause some confusion when ordering replacement pistons for a shovelhead engine equipped with 80 cylinders if you order a 010 oversize piston you will get a 37/16 010 piston that measures 3.4475 approximately and not a 31/2 010 that measures about 3.5075 the best way to make sure you get the correct oversize is to subtract 3.4375 3 7/16 from your finished cylinder bore measurement be sure that you know the correct size and order oversize based on 3 7/16 bore some pistons are supplied with wristpin clips while others come with buttons buttons must not be used with any piston design where the button is not fully supported pistons such as s&s series 92-2720 and 92-1620 are examples of designs which do not support the buttons compression ratio specifications are based on the assumption that unaltered crankcases cylinders cylinder heads and stock length connecting rods are used unless otherwise specified s&s connecting rod lengths are 7.440 for 1936 99 big twins the use of older stock 7.470 length big twin connecting rods will result in a slight increase in compression of approximately 1/2 point and may cause clearance problems in some applications clearances should always be checked s&s super stock® 31/2 and 3 5/8 bore pistons for harley-davidson® evolution® engines have specially shaped domes to match the complimentary shape of the combustion chamber in our super stock® cylinder heads these pistons must not be used with stock style heads to avoid contact between the piston and cylinder head the use of stock style flat topped pistons with super stock cylinder heads will result in very low compression and loss of combustion chamber efficiency to permit maximum piston skirt length flywheels used with 43/4 and 5 stroke s&s engines and sidewinder® big bore kits are 1/4 smaller in diameter than stock flywheels order toll free 866-244-2673 8-34

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