anyone ever flow test 383 A body manifolds say vs 383-440 hp manifolds

273 said

Highly doubt there would be much hp difference. There's been dyno comparison between hp and standard manifolds with no big differences. Same between 340/360/318 and magnum manifolds was like 5hp even shorty headers don't help much need long tube collector to make a decent difference especially once you start going with greater amounts of overlap.

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I think the old 300hp crate motor exhaust test is worthless. The cam in the stock Magnum 5.9 (which is the same in the 300hp crate motor) is so small that there were only minor differences in power between them all. But the cam was already limiting the motor so any difference the exhaust made was minor.

So I wouldn't use that test as the standard as to which exhaust manifold is the best on a 383.