Edrummr

iTrader: (1)

Specifically: PRC 220cc 5.3L Stage 2.5 CNC Ported Heads

How does the exhaust port on these heads match up with the ports on the stock '01 fbody exhaust manifolds? I'm just considering the port shape and alignment.
Would port matching be possible/worth while by removing material from the manifold ports?

Thanks!

Edrummr

iTrader: (1)

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PREDATOR-Z

You do not "port match" exhaust manifold to exhaust runners. Exhaust manifold primaries have to be larger than runner ports on heads. Reason is to minimise reversion, that extra "lip" formed would act as a barrier (instead of allowing reversing gases to straightly flow back in heads).

Edrummr

iTrader: (1)

Thanks for the response pred. I'll be minimizing IV/EV overlap to minimize reversion, but I guess I can see how flow in the "correct" direction might be more efficient than reversion flow due to a lip between exhaust runner port cross section being smaller than the manifold primary at their interface. I guess I do have a bit of difficulty imagining this as an effective check valve.
Since I am looking at ported heads, my main concern is that the exhaust runner ports in the heads may have been enlarged to the point that the lip may take the form of an "upward step" from the perspective of exhaust gasses attempting to exit the head.
Could you or any other experienced members speak specifically to that concern. Thanks again for all information.

PREDATOR-Z

1>1.5 mm lip is desired, so if the exhaust ports have been enlarged to the point that the manifold primaries are not in that range, enlarging the manifold primaries would be benificial (as well as deburring and smoothing out inside manifold runners especialy in the throat/collector area)

Edrummr

iTrader: (1)

Got it. Thanks for your help. I'll trace the exhust ports when I get the heads and modify the gaskets and manifold ports as necessary.

Cheers