[RodKnock]

Originally Posted by Excaliber

Rodknock says,,,


That would seem logical, considering the porkupine valve train layout, large oval style ports, etc. So I did just a quick and brief cfm flow check for various GM heads, including after market such as AFR. I like to compare flow data at 500 lift, so anytime I speak of cfm flow, thats my base line.

Surprisingly, GM heads are not all that great compared to the High Riser, not even the Tunnel ports, of Ford. In general it appears they flow about the same or LESS than stock High Riser heads, again, at 500 lift. I would have agreed with Rodknock initially on this, I would have assumed the big block Chev heads would easily outflow the big block Ford heads. Doesn't seem to be the case.

Also, it appears that making in excess of 500 horse with flow well below 300 cfm is certainly do-able. In fact, by the time you get to 300 cfm, or near it, those are some bad ass heads!

The reason I like to use 500 lift, maybe 600 lift, is because I have a "hunch" that is representative of a more typical street type application. Few street cars have a lift that exceeds 600, again, just a hunch. Flow data is a lot like dyno numbers, so many variables you do have to take it with a grain of salt, not hard data. Unless those variables are carefully spelled out.

Sorry, I don't believe you. Please specify which GM heads you flowed. First, most HP solid lifter cams from GM had more than .500 lift. Second, the square port (not the weaker oval port) heads are the high performance heads in the GM lineup. Third, there's no way a Ford high rise or tunnelport head outflowed a modern BBC AFR head (they have many from small to large cc's).

I would need to see data all the way through the lift range to believe you.