Page 293 of High Performance Parts for American V-Twins 2008 by S&S Cycle

1958-2008 50th ann iversary s&s® super stock® cylinder heads for 31/2 35/8 bore 1984 99 big twin 1986 03 sportster® and 1994 02 buell® models the first cylinder heads s&s introduced in 1994 were for 31/2 and 35/8 bore harley-davidson® evolution® big twin engines with stock crankcases as a result they are machined with a stock bolt pattern heads for sportster® models followed soon after these cylinder heads were designed to use a special piston in order to maximize performance gains head assemblies come complete with valves and s&s .640 lift springs but do not include the special pistons gaskets head bolts or manifold gasket kits are shown below please refer to the appropriate sections of this catalog for these other parts if required pictured right s&s pn 90-1802 ­ super stock cylinder head kit shown in optional black finish also available polished why special pistons a larger more open combustion chamber presents less resistance to air flow around the valves however in smaller displacement applications like 1200cc sportster models 80 big twin engines or even a 96 s&s engine a larger chamber will produce a very low compression ratio with a stock style flat topped piston the solution of course was to use a larger chamber for the flow with a domed piston to increase compression we designed a specially shaped combustion chamber and a piston dome shaped to match the contours of the chamber the increased squish area of this design sets up a controlled turbulence in the combustion chamber that turbulence improves flame travel for a more efficient burn and reduced detonation pistons are available to achieve various compression ratios features 2.000 intake valves and 1.605 exhaust valves special cast to shape intake ports with a special directional fin for improved air flow precision cnc machined from heat treated aircraft quality aluminum castings complete assembled heads include valves .640 lift springs available as bare sets fully machined but without valves or springs available in natural aluminum black powdercoat and polished specific models only finish pictured left the dome shape of s&s super stock pistons for 31/2 and 35/8 bore cylinder heads fits into the s&s combustion chamber to increase compression and to create a larger squish area for increased chamber turbulence order toll free 866-244-2673 8-10

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