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Join Date: Oct 2004
Posts: 41
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searched but no luck on compression numbers
I'm considering taking my 82 911 (62K original miles) for a compression test. What numbers should I expect to get? I looked all over the web and even on this board and haven't found anything deffinitive. My car runs strong and smooth, with no oil consumption, thogh there is a minor leak -quarter size after sitting for several weeks in my garage.
thanx |
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04-03-2007, 09:26 AM
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Friend of Warren
Join Date: Oct 2000
Location: Lincoln, NE
Posts: 16,493
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What you are looking for is the percentage of difference between cylinders. No more than a 10% difference between the highest cylinder and the lowest.
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Kurt V No more Porsches, but a revolving number of motorcycles. |
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04-03-2007, 09:29 AM
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quick response, thanx Kurt V
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______________ 2002 996 C4 Cabrio --currently engineless  1992 Carrera -Sold 1982 911SC Targa -Sold 1977 911 -Sold |
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04-03-2007, 09:36 AM
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I vaguely remember seeing about 140 to 160 psi on good running SC's.
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2014 Cayman S (track rat w/GT4 suspension) 1979 930 (475 rwhp at 0.95 bar) |
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04-03-2007, 10:26 AM
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Location: Rio Rancho, New Mexico
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I get 155/160# from my '85 Carrera and about the same from my '76 2.7 with 9.5 JE pistons.
This at 5200 foot elevation. I'd expect another 10 or 15 pounds at sea level. Unless you are way up in the mountains, I would expect no lower than 150# with a low mileage SC. Lower than 150# I would run a leakdown to see where it was losing compression. Good luck,
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DOUG '76 911S 2.7, webers, solex cams, JE pistons, '74 exhaust, 23 & 28 torsion bars, 930 calipers & rotors, Hoosiers on 8's & 9's. '85 911 Carrera, stock, just painted, Orient Red |
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04-03-2007, 11:26 AM
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WOW, does this seem right, or my mechanic didn't actually did the test? 35,45,45,45,40,45 respectively.
these numbers are way too low basing it on what you -good people of this board- are getting. I believe the test was conducted with the engine cold. The car runs absolutely great and no oil consumption or leaks -major- detected. plase advice, and tank you in advanced
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______________ 2002 996 C4 Cabrio --currently engineless 1992 Carrera -Sold 1982 911SC Targa -Sold 1977 911 -Sold |
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04-05-2007, 04:28 PM
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those will be other unit numbers probably
my mech told me that it is best to measure compression with more or less warm engine, 100% batteries, all spark plugs removed, and with the pedal pressed down fully.
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before: '69 Porsche 911T bahama yellow now: 1981 911 SC Targa winered |
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04-05-2007, 11:55 PM
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Location: Capistrano Beach, Ca.
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Jan is probably correct--other unit numbers. The key is the difference between cylinders as Kurt mentioned. Retest at optimum conditions as mentioned by jan, and note differences. As shown, the #1 cylinder (35) is out of spec.
Larry
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L.J. Recovering Porsche-holic Gave up trying to stay clean Stabilized on a Pelican I.V. drip |
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04-06-2007, 08:05 AM
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correction -and less alarmed- the numbers are 130, 140, 140, 130, 130, 135. Are these more or less within acceptance? Since they were going to remove the plugs, I had them replace the spark plugs, and wires (expensive!!!), air filter and oil change. Nice! -for me, not for my wallet.
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______________ 2002 996 C4 Cabrio --currently engineless 1992 Carrera -Sold 1982 911SC Targa -Sold 1977 911 -Sold |
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04-06-2007, 02:24 PM
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1979 Porsche 930 3.4
1969 Porsche 911T 2.0L T
