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Thread: 5.7" vs. 6"
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Old 01-17-2006, 08:29 PM
onovakind67 onovakind67 is offline
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This study has nothing to do with dyno data, it is a study in the actual geometry involved. The angles aren't somebody's theory, they are calculated using simple math.

I can't see any difference between his definition of 'dwell' and yours. You use .050" as your dwell standard, he uses .250" as his.

If you calculate the piston displacement at 15 from TDC you will find:
A 3.48" stroke with a 6" rod has the piston 0.0762" down in the bore.
A 3.48" stroke with a 5.7" rod has the piston 0.0771" down in the bore.
Note that there is less than .001" difference in piston displacement.

A short rod has better leverage on the crank which helps it produce more torque at lower rpm's. The same effect that causes more cylinder wall loading, also causes more crankshaft loading. Note that a shorter rod has a mathematically longer effective stroke.
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