[Chevy454]

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I have the 143 Crane made cam and it doesn't run worth a darn with the manifolds and the correct dual exhaust .But it sounds good .I need to try headers and a twin muffler set up and see what happens .

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I don't wanna sound like a *douche*, but I'll say there's a good chance it ain't the manifolds/exhaust that's hurting the performance...even if it's the original 2.5" exhaust [actually <2" in spots] it'll still let a BBC do it's thing.