Page 290 of High Performance Parts for American V-Twins 2008 by S&S Cycle

top end continued ­ cy lin d er head s stock compatibility and then some valve angles and valve tip locations are the same as stock so any stock or aftermarket standard or roller tipped rocker arms can be used performance replacement heads are set up to handle cams with up to .640 total lift and with tdc lifts of up to .252 intake and .210 exhaust we recommend that all clearances be checked with high lift cams especially if the heads have been decked to increase compression good news for owners of fuel injected models the front head is machined to accept the stock cylinder head temperature sensor which allows performance replacement heads to bolt onto efi engines s&s® performance replacement cylinder heads this photo shows the directional vane in the intake port of an s&s performance replacement head this vane splits the air stream ahead of the intake valve reducing port turbulence which allows for increased flow available kits and finishes s&s performance replacement cylinder heads are available in natural aluminum and black wrinkle powdercoat finish heads are sold in kits of two heads complete with valves and springs complete heads are also sold individually as a repair item however it is not recommended that a single performance replacement head be installed on an engine with one stock head the resulting imbalance in compression ratio and power output could result in excessive engine vibration features optimized for smaller displacement engines chamber designed for stock style flat topped pistons slight increase in compression 8.8:1 in an 80 motor port design increases flow while maintaining velocity compatible with up to .640 lift cams efi compatible available in natural and black wrinkle powdercoat size matters but sometimes it hurts there is a tendency to try make everything bigger in the belief that it will be always be better if a little is good it doesn t always hold true when talking about the size of ports and valves we have to consider the displacement of the engine and the effect that port and valve size will have on velocity velocity is critical to the performance of an engine it takes velocity to carry entrained fuel droplets into the combustion chamber and velocity gives air the momentum to keep filling the cylinder even after the piston has started traveling back up the cylinder on the compression stroke velocity keeps exhaust gasses flowing out the exhaust pipe even after the piston has passed tdc on the exhaust stroke large ports work well on big inch motors but can hurt the low rpm performance of smaller engines because velocity is reduced flow comparison chart cylinder head type stock harley-davidson® s&s® performance replacement s&s super stock® valve diameter intake 1.840 1.900 2.000 exhaust 1.610 1.575 1.605 .600 lift flow 10 intake 125 cfm 142 cfm 158 cfm exhaust 98 cfm 109 cfm 122 cfm s&s® gasket kits for s&s performance replacement cylinder heads engine and bore size 31/2 bore big twin 35/8 bore big twin part no 90-1905 90-1906 msrp $26.95 $26.95 s&s® replacement cylinder heads for harley-davidson® evolution® big twin engines finish natural aluminum black powdercoat complete with valves and springs head kit 90-1201 90-1221 msrp $894.95 $979.95 front 90-1201f 90-1221f msrp $536.95 $587.95 rear 90-1201r 90-1221r msrp $536.95 $587.95 no valves or springs head set 90-1200 90-1220 msrp $694.95 $779.95 8-7 visit us at www.sscycle.com

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