Head porting question

[menlatin]

Ok, this isn't particularly a buick question, its a question about head porting for turbo motors. I've got a turbo 388 stroker in the works, and i'm getting ready to start porting the heads. They are pro action 235cc runner with 2.08/1.60 valves. Current as cast flow is:

Intake Port Test Data @28" of water
.100 .200 .300 .400 .500 .600 .700
73.43 138.35 195.66 243.12 274.02 292.11 312.38

Exhaust Port Test Data @28" of water
.100 .200 .300 .400 .500 .600 .700
60.22 114.27 151.72 177.80 192.02 194.13 197.24

Our cam is a custom solid roller cam from comp, specs being:
280/273 advertised, 242/236 @ .050, .608"/.602", 114 lobe sep.

Now, i was told that smaller exhaust dur. was to provide for exhaust gas speed to help spool the turbo fast, but I think that if we have a turbo with, say, a .96 or closer to a 1.2 AR, then the sheer large displacment of the motor would be able to spool a turbo of that size, quite quickly even with a large exhuast lobe, but i don't really know. So, i dont know if i should port the hell out of the exhuast to get crazy flow numbers (230cfm @ .600) or just leave it moslty as is? I also plan on getting the intake to a little over 300cfm @ .600.

Oh yea, our power goal is 900hp @ ~ 15 psi with water injection and pump gas.

 

[KendallF]

Hog them out. The short exhaust duration is more about preventing reversion than anything else. The S2 heads have huge exhaust ports and the better they flow, the faster the car goes. The turbine A/R will have a lot more to do with spool characteristics than exhaust port size, IMO.

Sounds like a cool project, by the way.

 

[The Radius Kid]

I'm with Kendall on this.
I'd be looking for 80-85% exhaust to intake flow ratio.
What RPM range you gonna run this engine in?

 

[menlatin]

well Desktop dyno is giving me figures of peak power @ ~6000 which i think kinda sucks, but tahts just what it says. I mean i dont know how accurate it is, but thats all i have to work with. I guess the 6k peak hp is becuase of the longer stroke, but it seems like to me if you keep the boost going and its got straight through exhuast it should be be able to atleast 6500. Any one have a similar motor that wraps out higher? our's is 3.75 stroke, 4.06 bore. Or do you think maybe our cam is a little small to wrap that far?

 

[G-Racer]

Shape is more imoprtant than size and velocity is more important than flow particularly on the exhaust. Keep that in mind. If you are looking for a professional job give me a call.