Total stock intake, good valve seat and guide, ZERO modifications
.050" lift 27.3 cfm
.100" lift 52 cfm
.200" lift 103 cfm
.300" lift 149.5 cfm
.400" lift 164.6 cfm
.500" lift 168.5 cfm
same port with epoxy molded in and around head bolt boss
.050" lift 24.5 cfm
.100" lift 47.8 cfm
.200" lift 102 cfm
.300" lift 151 cfm
.400" lift 177 cfm
.500" lift 190.2 cfm
Just like you said Tom, it takes over .300" lift before you see any gains from the modifications. With a stock cam or even a slightly bigger one, the gains are minimal. These test were done with a stock diameter valve. I couldn't find the paper we were writing on for the exact number, but during the test we pulled the valve clear out of the hole to test just the port. It wasn't much more the 190 cfm we got at .500" lift. The seat area was the restriction on this head. Even with a stock 1 barrle intake bolted to the head, the flow numbers didn't change.
