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Thread: RPMs and road speed

  1. 02-14-2021, 02:47 PM #1
    David 23
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    RPMs and road speed

    Our 1972 911T has a RS Spec 2.7 engine built from the original 2.4. I am not certain of how stock the transmission is. At 80 mph (not speedo, but GPS indicated) in 5th gear the car turns 4k rpm. Does this seem to be normal RPM/speed?
    1972 2.7 RS spec 911T, Aubergine
    1979 911SC backdate 3.2SS hot rod
    1974 914-6 2.2
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  2. 02-14-2021, 03:39 PM #2
    kentf14
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    Seems about right, but take a look at the chart in the back of your ‘72 manual. Depends on whether you have the stock R&P and stock gears. Here’s the page from my ‘73 owners manual.
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  3. 02-14-2021, 04:59 PM #3
    Arne
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    Seems a little on the high side to me, both from memory and by the gear charts. But the gear charts assume stock tire size. What size rear tires are you running? If they are shorter than stock, 4000@80 could be accurate.
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  4. 02-14-2021, 06:11 PM #4
    David 23
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    I'm running CN36, 185/70/15. I should probably triple check my tire pressures and do some more accurate readings. It could be my tach is off a bit too. It just seems that 4K at freeway speeds seems a bit high. Of course the up side is it sounds great, and terrific passing response!
    1972 2.7 RS spec 911T, Aubergine
    1979 911SC backdate 3.2SS hot rod
    1974 914-6 2.2
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  5. 02-15-2021, 06:11 AM #5
    gled49
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    Here is my 73, 7:31 R&P, 29:22 stock 5th, 185/70’s, very accurate odo. G
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  6. 02-15-2021, 06:20 AM #6
    gled49
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    Same car with 28:23 5th. G
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