looking at these dyno charts (and everyone elses)cams seems to be the biggest improver (for the 865 motors), followed by getting away from the stock pistons. If I read the dyno chart (in this thread) info correctly, all of the runs are with the 813 cams, that would make a big change even with the stock pistons. It would be interesting to see a 904 vs 865 with everything being equal dyno comparison. It is a pretty small increase in displacement, it should be possible to get pretty close to the same power out of both.
although if you go to the effort to change out the pistons, and for a couple of bucks more do the 904, why not.
05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter
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