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Location: San Antonio, TX
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964 compression test results
Cylinder psi leakdown
1 190 5% 2 195 8% 3 190 5% 4 195 8% 5 198 8% 6 195 5% Are these numbers good, or are they the beginning of the end of this 964? It is a 93 with 107,000+ miles.
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Paul 1980 911SC Targa - Sold 1972 914 - Sold |
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12-18-2007, 07:20 PM
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12-18-2007, 07:30 PM
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It's not even the beginning of the beginning for your engine.
-Andy
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72 Carrera RS replica, Spec 911 racer |
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12-18-2007, 09:30 PM
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If you are really worried about this, don't! These numbers are fine - actually a little better than fine. The most important factor in a compression test is consistency between cylinders. A good rule of thumb is to have no more than 10% variance between the cylinders. You are looking great in this regard with about a max of 4% between 1 and 5. Good cylinder leakdown readings should be below 8%. You are on the high end here but that is by no means "the beginning of the end". You've got many, many miles before you'll need a rebuild. If I were you I'd just drive and not worry about it. After all, what else is there to do in Del Rio! I spent a summer there in 1983 doing an Air Force training program. It was a pretty sleepy place back then. Merry Christmas.
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Please help the MFI community keep the Ultimate MFI resources thread and the Mechanical fuel injection resource index up to date. Send me a PM and I'll add your materials and suggestions.  1973 911E Targa (MFI) Last edited by David E. Clark; 12-19-2007 at 06:48 AM.. |
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12-19-2007, 06:44 AM
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I think 1% to 3% hot leakdown is ideal. These numbers, especially bundled with compression results are acceptable.
Oil consumption rate would tell you more about necessity for top end rebuild. Is that info available? I would not assume because you have acceptable compression and leak down that you are not in need of valve guides. Not trying to scare you, but I bought a non running 3.6, which was supposedly rebuilt. I had to pay for a complete rebuild again. Proceed with caution. Doug
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12-19-2007, 07:30 AM
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After that many miles, producing those numbers means they were well maintained miles. This would indicate proper driving, oil changes, and warm up cycles. I would say its unreasonable to find any better numbers on a 110,000 mile engine.
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12-19-2007, 08:33 AM
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The car is immaculate. These numbers are from a car I'm considering buying.
I'm moving to CA this summer so I know I'll have more choices out there. I don't know if this is the best time to buy though. Have you seen house prices in CA!
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Paul 1980 911SC Targa - Sold 1972 914 - Sold |
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12-20-2007, 07:01 PM
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The compression numbers look darn good. The leakdown isn't spectacular, but certainly not anywhere near a deal-breaker situation. They are consistent, that's the main thing, and you don't know how accurate the testers gauge was either. Higher than 8% and I'd start to do some more homework....
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Chris ---------------------------------------------- 1996 993 RS Replica 2023 KTM 890 Adventure R 1971 Norton 750 Commando Alcon Brake Kits |
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12-20-2007, 08:53 PM
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The leakdown numbers are fine. I would concern myself more with where the leak is occuring.
Also, was the motor warm, hot, cold? This also plays into the equation. If you pay for a leakdown, and the shop/mechanic does not tell you where the leaking is occuring, kindly ask for your money back..... Cheers
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Turn3 Autosport- Full Service and Race Prep www.turn3autosport.com 997 S 4.0, Cayman S 3.8, Cayenne Turbo, Macan Turbo, 69 911, Mini R53 JCW , RADICAL SR3 |
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12-20-2007, 09:49 PM
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Compression and leak-down tests
I had a friend help me doing compression-tests on my old 2.7. The compression on all cylinders was 9:1 and it came straight up, it didn't need the engine to turn several times to get there... My friend was wery impressed by this, but this is by no means a leak-down test, what is the difference?
And if the compression on all cylinders is even and good, can there still be problems? |
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12-21-2007, 05:53 AM
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1970 Porsche 911 S 
