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Join Date: Jan 2003
Location: Atlanta, GA
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Low compression numbers due to valve, why?
Looking at a turbo, maybe.
Lower compression in one cyl. due to an intake valve... what would cause this, would it need immediate replacement?
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Brad Tompkins Current: '86 951 Sunroof Delete - '89 951 - '83 944 Spec - '08 Cayenne Turbo Past: '88 924S Track - '86 944 16v - '87 951 - '87 951 - '88 951S - '08 Cayman S - '87 944 Track - '93 968 |
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07-14-2003, 03:01 PM
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What test was done to clearly indicate an intake valve as a problem?
Could be a scored cylinder/bad rings.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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07-14-2003, 03:12 PM
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Location: Cordova, TN
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Burnt, cracked, or bent valve could cause compression to leak. I am not sure about the 944 valve train but a broken, collasped, or cracked valve spring could also cause this problem. Alot of carbon build up can also prevent a valve from sealing properly.
SoCal has a good point though it could be the cylinder/rings. I would also suggest a bad head gasket. Head gaskets seem to be a common problem on these cars.
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Roger Hall 81 924 N/A Some people are like Slinkies. Not really good for anything, but you still can't help but smile when you see one tumble down the stairs. |
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07-14-2003, 05:07 PM
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It was a PPI so I'd assume the results were from a leakdown...
What exactly is a burnt valve? The car still runs fine, so I doubt it to be a bent valve... And wouldn't a bad spring cause real problems at high revs?
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Brad Tompkins Current: '86 951 Sunroof Delete - '89 951 - '83 944 Spec - '08 Cayenne Turbo Past: '88 924S Track - '86 944 16v - '87 951 - '87 951 - '88 951S - '08 Cayman S - '87 944 Track - '93 968 |
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07-14-2003, 05:14 PM
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Location: Cordova, TN
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I have never had either problem so I am not sure, but here is my understanding.
A burnt valve is caused when the valve becomes too hot, and the heat causes the valve to deform. Bad springs should affect an engine at any RPM.
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Roger Hall 81 924 N/A Some people are like Slinkies. Not really good for anything, but you still can't help but smile when you see one tumble down the stairs. |
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07-14-2003, 05:29 PM
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Only the exhaust gets "burnt". This is where there is a small bypass at the valve (cracked valve seat or a bit of debris like a lost washer) and the exhaust gases scours a bit of the seat and/or valve. this grows till there is almost no compression on the cylinder.
A leak down will tell you real quick if it's the valves or the rings/cylinder wall. Having an intake leak is very rare unless there is something stuck in the seat. Then there could be a bit of burning but most likely predetonation of the intake gasses resulting in some serious damage.
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Hugh - So Cal 83 944 Driver Person NOT a 'real' Porsche -- Its Better!!!! When was the last time you changed your timing and balance belts and/or cam chain and tensioner? New Users please add your car's year and model to your signature line! Never break more than you fix! |
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07-14-2003, 06:33 PM
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1983 Porsche 944 2.5 liter
