[Half-Inch Stud]

Jim, Gach,
I read this thread for the first time tonight - intrigued.

Some quick hits: I tried Fowmasters for about 1 hour on my 455/[Ultradyne 255/263 with 104/104 Lobe centers]: Sounded like a Chinook on takeoff! Had the fella weld on the Walker Sup-Dyn-Turb's and then the sound was manageable.

Jim, The exhaust config we discussed earlier this year was built-out and sent to Kauffmans. Dyno said better than manifolds, not quite as good as 4:1 headers, on a 300HP motor. Early feedback from Jeff was that my 1-5/8" piping was probably too small. I agreed, as it was all I could find. Still looking for the evalation on a 550HP motor. Glad to see you are equally discerning on the exhaust requirements for 500-700HP ponchos.

I need some 2" early-Bird headers to continue the development. I think it will bear fruit.

The X-cross ought to be better than the H-cross, as long as the system needs it. Probably good for equal 4:1 headers. My guess; not show benefit for Early 421-SD manifold, Tr-Y configs, or even the Long-Branch manifolds...My header config should NOT need it as I've timed the pulses as equally as practical.
My simulations showed that the Heads' exhaust crossovers are a real problem for Big-time charge contamination; Cyl 4 contaminates cyl 6 and Cyl 3 contaminated cyl5. Need to block cyl 6 and cyl 3 and run a straight-pipe under-Intake crossover. Practically speaking we'd all fully-block the heads crossovers for cooler running heads/engines.

How many of you'z guys are running low 12's or better, with open exhaust crossovers [worse-yet with sheet metal plates blocking it?


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"his peg-leg got woodworm , and broke into three"--G. Baker