318 Port match heads to Performer RPM Intake
If you really do some digging, there are examples out there where this type of mismatch....... where the intake is bigger than the heads........ and after being corrected........ has actually resulted in a loss of power(before and after test on the dyno).
And some of the mismatches are way more extreme than what you get with 318 heads and a 360 manifold.
Like...... oval port BBC heads with a rectangle port intake(about a 3/4” mismatch).......or a BB ford cobra jet intake on std port heads.
MP used to sell an iron 2bbl intake manifold for w2 heads.
It was nothing but a non-egr 360 manifold with relocated bolt holes.
The ports were still std 360....... which is a horrible mismatch with w2 heads.
The instructions stated to not bother trying to match the intake to the heads, as it would make no difference in power.
It “seems” like blending makes sense, but a lot of what goes on there isn’t intuitively clear.