Head porting question, One for the engine experts :-) Options

[Bob Wolcott]

I have a dilemma. I am in the precess of rebuilding my mechanical injection throttle bodies

http://oregonstate.edu/~wolcottr/Porsche/Intake/

and the bores are not matching up well with the intake ports, and it is not due to machining error. The ports are not coincentric with the TBs and the ports appears to be a bit larger than the throttle body bores. These heads have been ported though not much has been done toward the entrance of the port, mostly by the valve guides.

My question is... would it be best to bore the throttle bodies out even larger (37mm, maybe 38mm) and then contour the port for a perfect fit to the throttle body, or should I leave the throttle bodies as is (36.5mm) and do the best I can with the ports, or just leave things as-is and not touch anything?

The coincentricity error is ~.025 or so and the engine is out of the car and the heads will be coming off anyways. The motor is built to RS specs.

Thanks,
Bob

[ChrisFoley]

Would it be possible to slot the mounting screw holes in the TBs to improve the concentricity? If so, I wouldn't worry about a small mismatch in bore size as long as the intake air doesn't run into a step at the transition. (ie. undercut - ok, shelf - ng)