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Thread: What brings RPM limits...

  1. #21
    Member
    Join Date
    Jun 2016
    Location
    Canada
    Posts
    42
    Aaah what a read!

    I wonder if things changed over the last 10 years.

  2. #22
    Junior Member
    Join Date
    Sep 2017
    Location
    New Zealand
    Posts
    17
    And 5 years further on, what a treasure trove for the enthusiast engine builder! Sad that Grady Clay, Chris Seven and Steve Weiner are all no longer with us. Please PELICAN don't lose this information trove!

  3. #23
    Member kent olsen's Avatar
    Join Date
    Sep 2010
    Location
    McMinnville, Ore
    Posts
    69
    Well I've had my 72T for over 20 years. Since I'm a road racing nut, I started out autoxing, well before I got my Porsche. Then I got into driving at the "track" days. With the help of 'Mike Bruns' in Florida we came up with a 'bullet proof' engine. I had found a 1981 3.0L before I left the west coast for Florida. Mike helped me build this engine, twin plugs and webers and able to turn 8500rpm. However, driving on a race track I found it's torque that pulls you out of the turns, sooo. With the help of another friend with a 72 track car, I contacted Dougherty racing. He had a cam, I think it was a 902-102, that had a lower torque peak, about 4600rpm and 230 ft/lbs and max Hp at 6900rpm. Now when I'd downshift my 915 transmission I'm at 4-4500rpm and it will pull like crazy out of the turn up to the redline, I use, of 7200rpm. I've run this engine for over 10,000 miles and all I have to do it adjust the valves and change the oil once a year.
    Kent Olsen
    McMinnville, OR
    72 911 upgraded 3.0L
    RGRUPPE # 104

  4. #24
    Senior Member
    Join Date
    Oct 2010
    Location
    Southern Ca.
    Posts
    1,166
    I like these old posts . I do know that the 70.4 RSR crankshafts have a bigger radius on the main journals , not the rod journals .

  5. #25
    Senior Member
    Join Date
    Feb 2011
    Location
    Northern VA
    Posts
    567
    Boy, some real heros of these motors posted on this great thread; some no longer with us. Long live the kings!

    That said there are limits to these motors that are not just mechanical. It's a 2 valve overhead cam motor; most will reach reach peak HP below 8k. You might be able to turn them faster and survive with remedies to valve train, crank and oiling; however, horsepower will likely be dropping off. There is a reason why porsche has tried to live within these limits on 2 valve motors.

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