When I first flowed these heads, with std. magnum valves they went 247 cfm on my bench.
That was untouced seat and valve. Backcutting the intake valve did almost nothing!

I am surprised at how well they flow with just a 2.02 valve and valve job done, but I've tested 4 different heads so far and the worst was 264cfm @.500 lift and the best was 268cfm. At .550 lift the worst was 269 and the best was 272.
They all stall at the .565 mark.

When I do a flow test I always check for leaks so if I had any problems I would have known before doing any testing.
If you run the flow #'s from my bench with the dual plane intake on the RHS heads, and run the #'s we got from our dyno test through pipemax, they correlate? very well showing we needed approx. 230'ish cfm to make 485HP and they flowed 234cfm at .500 lift and 229 cfm at .460 lift.

Kind of funny because the flow bench said the bigger SV intake flowed so much more than the dual plane the engine should have made more power at some point...but it never did!