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Thanks Snowman I didn't realize that. I had purchased an E MFI unit and was looking at modifying slightly. As I understand it my "T" heads have 32 mm intake/exhaust ports, while the valves on all 911s of this vintage are the same (~41/46 I think). I noticed that the "E" heads of this time (1972) use the same ports as the "T" and only the "S" uses 36 mm ports. I was thinking of going to the middle ground and porting the heads to 34 mm.
As far as the MFI unit is concerned I measured the plastic velocity stacks and throttle bodies last night. The throttle body is ~31 mm on the engine side and 34 mm on the velocity stack side (if my memory serves me well). The velocity stack is 31 mm on the throttle body side and 38 mm at the top. Therefore, it seems like some mis-match between these different flow areas. I know that the bore on both the stack and TB is not straight to create a venturi effect. I was considering opening up the TB on the head side to 34 mm (to match my head porting) and port matching the mating surface of the body and stacks.
Any thoughts?
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