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Low compression, should i rebuild?

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Old 03-15-17, 09:11 PM
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Low compression, should i rebuild?

Hey i recently aquired an 85 gsl and i was told it didnt run and wouldnt go over 10mph. Well i got it home and it runs snd drives just fine but i noticed the compression was low like 75psi on each rotor and 10psi per rotor face. Is it safe to drive this the way it is or doesnit require a rebuild?
Old 03-15-17, 09:12 PM
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do the test correctly, without the schraeder valve in the hose.
Old 03-15-17, 10:04 PM
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The engine my have a lot of carbon build up in it. If so it can cause low compression from Seals getting stuck. I have seen
a 85 13b 6 port get damage from this. But if you like the car why chance it? To me there is only one way to know it's good thats to rebuild it.
Old 03-17-17, 06:53 PM
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welcome to the board.

yes, i agree with post 2. make sure you conduct the test correctly. you mentioned that it ran and drove "just fine" when you got it home, so i am a tad bit skeptical until you have a test confirming low compression.
Old 03-17-17, 10:13 PM
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i wasn't saying it didn't have low compression though, it did come back with only a 75psi cumulative figure but it's good to know where you are starting from.
Old 03-19-17, 09:25 PM
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Hello just wanting to know how much it cost to rebuild a stock s4 engine. I am just wondering
Old 03-19-17, 09:40 PM
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~$1k if you do it yourself, $1500+ to have a shop do it for you.


really depends on the condition of your existing engine as well.




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