Exhaust Manifolds

My engine has been fully re-built with lots of extras such as 4 BBL Carb, Edelbrock Performer Intake, larger valves in the heads, 30 thousandths over on the pistons etc.

The BARR marine exhausts were reconditioned and being used, but I've read on this Board where the "old style" put a lot of restriction on the performance.

Can they be Ported with any success?

What's a better performance exhaust manifold?

64'
Not knowing what which Barr exhausts you have and whether they're the older smaller +/- 2-1/4" or the 2-7/8 to 3" hose size, it may not make a lot of difference for you to move to something less restrictive. On a significantly modified engine, I gained about 100 rpm going from small to large exhaust hose dia., and about the same gain again when swapping to the larger exhaust manifolds. I'm using the ones that John provided the thread on above (but not on the boat shown below). You can port your existing manifolds at the ports to make sure they're at least as large as your head exh ports. In my opinion it really depends on how bad/small your current ones are and your degree of modifications to the engine.