Quote:
Originally Posted by Mohawk
Re the stroke, unless the 250 & 300 blocks are different heights, the stroke is irrelevant.
It is my understanding that the 250 & 300 use basically the same crank, as they are interchangeable between crankcases. The 300 uses a 4mm further offset crank pin, giving 8mm more stroke, but a shorter connecting rod to maintain the same TDC piston stop height.
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Uh, no, do maths and you'll see difference. Longer stroke on 300 gives larger displacement volume. This volume will then be compressed into roughly same CC in head. Therefore, same 250 pistons will give higher compression on 300 engine.
Just because Wiseco designed 250 & 300 to yield same 12.5:1 compression does not mean pistons are same. Dome on 300 12.5:1 piston is much, much flatter and lower than 250 12.5:1 piston. About 5-7cc less dome on 300 piston from rough look of it. There's absolutely not enough material in 250 piston top (3.5-4mm) to remove enough to reduce compression of 250 piston inside 300 engine.
Plug in numbers on this calculator and see for yourself:
http://www.diamondracing.net/tools/
Eagle Rods has even better calculator, but appears they've moved it or taken offline.