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Some clarification
Ok, I have done some research on the 3 engines that I have access to and here are the findings:
1979 USA 3.0 w/case # 930/04 or 06
Intake runners = #911 110 169 4R(larger)
Fuel Distributor = unknown #
port size (from BA's book) = Intake
39mm, Exhaust 35mm (largest intake produced)
CR = 8.5:1
1983 USA 3.0 w/case # 930/16
Intake runners = #911 110 169 2R (smaller)
Fuel Distributor = Bosch #0 438 100 077
port size = Intake 34mm, Exhaust 35mm
CR = 9.3:1
1981 Euro 3.0 w/case #930/10
Intake runners = #911 110 169 4R (the big ones)
Fuel Distributor = Bosch # 0 438 100 097
port size = Intake 34mm, Exhaust 35mm
CR = 9.8:1
All engines have the same 49mm Intake and 41.5mm Exhaust valves
In summary, the 78-9 has big runners and big ports but the lowest compression. The 83 USA has smaller runners and ports and slightly higher compression. Both engines yield the same 180HP and 175ft. lbs or torque.
The Euro engine has big runners feeding the smaller ports. The magic must lie in the squeeze of 9.8. The wild card is the fuel distributor which I can't see making that much of a difference. The Euro produces 24 more HP and 14 more pounds of torque. You can time the cams and ignition all you want and not get that kind of increase from the USA versions.
Footnote: The ultimate "cheater motor" would presumably be to marry the biggers port to the large runners and Euro P/C's. The dyno would tell, but then why did Porsche abandon the larger ports after 78-9?
-Mike
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