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Thread: 5.7" vs. 6"
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Old 01-17-2006, 08:18 PM
56Maynard 56Maynard is offline
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That is an informative study. The only part I don't follow is his reference to "Dwell time". He measures dwell time as a number of degrees to TDC with the piston in the hole a quarter inch. This measurement would seem to have little to do with dwell time as I understand it. The correct dwell time comparison/measurement would be the number of degrees (before and after) TDC it takes to make the piston move a predetermined amount (like .050 for example). He seems to desregard the fact of the slower moving piston with the longer rod while it is in this area of TDC building cylinder pressure. He does mention that the short rod made more power from 2000-4000 rpm which I am having difficulty understanding. It seems that the piston falling away relatively faster would reduce cylinder pressure not increase it. This presumed reduced cylinder pressure coupled with a slightly reduced mechanical advantage of the piston over the crank pin should lower torque from 2000-4,000 rpm and beyond. Its too bad this guy didnt ask Smokey for his dyno data on the long rod theory.

At any rate, I think that when the Smoke said to use the longest rod you can fit in there, he was talking about all out racing anyway. I don't think you could really know the difference in a street motor anyway but if you gotta buy rods and pistons, you might as well buy long ones if it makes you happy. As long as they all cost the same that is.
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