Horse power drop using early A 273 manifolds

pishta said
It may not be the 273 rear firing manifolds killing it, but the F'd Y-pipe they used off of them, that kinked 90 was nasty! Then you had this..and that. Although it worked pretty good for a 273. Pics courtesy of @cosgig

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Yikes! Lucky for me on my 318 in an early A with the 64-66 wrap around manifolds I have a dual 2-1/2” exhaust. So the manifold is the restriction.