There was a thread here from maybe 2-3 years ago where the build was some sort of 500” stroker with TF240 heads and a 6-bbl intake with a hyd roller cam designed to supposedly be ex manifold friendly......... and as I recall the power difference between the headers and manifolds was in the neighborhood of 90hp.
....and, if I remember correctly, the cam choice, although believed to be a good choice, really was not that great of a choice.
I think when they bolted the manifolds on and the motor lost 90hp........ that’s when it became pretty apparent the overall combo may not have been fully “optimized” for exhaust manifold use.
I think the slow hydraulic roller ramps and pretty big seat timing hurt that motor's manifold potential. It had like 83° overlap at the seat. I target 55° or less depending on the motor. Bracket guys successfully live and die buy a cam's 0.050" numbers. Manifold motors seem to care about actual seat timing.
And certainly you cannot argue with the header advantage in that example. I just don't think you're going to get 680 HP out of any manifold motor with any cam and a bunch of Summit Racing parts slapped together like you could do with a header motor.
