Did you gasket match the manifolds ? the last set I worked on the openings were almost an 1/8" smaller than the gasket which is what the heads were matched to.
I have a manifold that Dwayne worked on for a low deck ... and an acid ported 70 383 intake ... plus a set of extrude honed, jet hot coated A body 383 Exh manifolds ...
my FAST builds never materialized ...
I did do a little gasket matching and cleaned up the casting flash on the exhaust manifolds but, I did not go crazy.
Around the time I was grinding on them I read some stories of people's manifolds cracking from being thin so; I pretty much stopped where I was at (kind of worried me). It is primarily a street car and I figured the extra material for strength in my situation is probably better than the few HP's I would gain.
