Exhaust port shape

[wilson1970]

Do i need to match exhaust port on Sportman 11 heads for 355 SBC to Fel Pro gasket. Currently port is .150 smaller than gasket.

[KnightEngines]

No, size the port to suit the motor, not the header.

[Ron E]

Its been a while on those, but my vote is no. The opening in the head is very unlikely to be a flow issue. And, making it bigger is just expanding/slowing the flow that hasn't had a chance to reorganize after getting around the valve, guide boss all while executing the turn. From the valve job to, and past the guide and short turn is where I'd concentrate my efforts. But, that's just me. Others may have different approaches.

[randy331]

Don't ever gasket match anything.

What does a gasket know about proper sizing of a port ??

Randy

[mag2555]

Your post is accutally about size, not shape!

That work is not needed ,as the main restriction is the Throat of the valve bowl which had far less area then what is at the flange.

Having that mismatch will also pick you up 3 to 4 % more exh flow above .300" lift and in the process cut back on reversion which will help to make the motor come on the Cam sonner , as in widen the power band!