Quote:
Originally Posted by Bob
I fully understand how the new valve rule changes the cc of a head. But as you pointed out, milling the intake or exhaust face and sinking valves for clearance will make the runners smaller. And, the new valve rules will make the runners bigger. Should one balance the other, maybe. But when your runner cc's aproach 10%-15% over the published SS spec, maybe they are just a little to big.
Yes, I do see your point. But do we really know that NHRA does not have spec's? Spec's that they aquired from virgin heads? They have spec's for wheelbase, for example. They are not published, but they have spec's.
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I know for a fact that NHRA does not have all the cylinder head volume specs from virgin heads. As a matter of fact, many of the volumes in the SS list are from cylinder heads that were already ported when they did not even have a spec available for a stock virgin head and when it was still illegal to port heads in SS. By the way, at one time, I used to be an SFI NHRA Tech. Terry Bell who goes under the X-Tech-Man in this forum also knows about this issue and has made very valid points on this issue before.