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Compression testing my '89


fun car guy

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I'm thinking of replacing all the brake and fuel lines on my '89 which is a lot of work and there's no sense doing it if the engine is burning oil even though I don't see the oil level going down, the oil pressure averages 45 psi and there's no smoke coming from the exhaust.

I need to know what the correct cylinder compression (psi) should be on a car with 1,160 miles and can't seem to find that in my factory manual.  The new plugs I installed seem to carbon up a little but then I haven't been able to drive it much because of leaking brakes, it's been mostly just idleing.

Maybe it just needs to be driven as it's been basically idle for about 4 years now?

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You can compression test at any time. I don’t remember any specific number but in almost all cases, balance between cylinders is most important.

Aside from that, driving it as it is intended should give a good indication if further investigation is needed. 

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Thanks, 2 seater but I was after an idea as to the compression on a healthy engine.  During the one time I drove the car it seemed to excellerate fine, no smoke or hesitation but now that the brake line has sprung a leak, I can't drive it at all.  Replacing all the lines should make it so I can actually give it a good run exposing more gremlins.

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Someone else may need to answer the specific question if you are looking for actual numbers. Only from memory because my build sheets only include the physical specs of the mechanical assembly of the engine. My three engines are all different compression ratios, so I cannot even venture a guess. I do believe my 9.5:1 one tested at ~205psi, but this is definitely not a stock engine. Too high is not always a good thing either. It may be caused by lots of carbon buildup. Consistency is most important.

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I bought a used engine from a salvage yard and their testing was all the cylinders were in the 175 range. I am in the belief that to be about where you want to be.

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4 hours ago, DAVES89 said:

I bought a used engine from a salvage yard and their testing was all the cylinders were in the 175 range. I am in the belief that to be about where you want to be.

175 psi, huh?  Thanks for the info., I'll report my finding when I have them but I'd hste to do the cylinders next to the firewall, damn hard to get at them!

 

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Thanks guys for your helpful information. 

I went out to the garage and fired the old girl up only to be greeted by gas leaking from the pressure relief valve on the forward fuel rail.  It has never done this before so it's yet another thing to deal with. Anyway, I was going to do a compression test with the set l I bought online (fool, me!) only to discover the plug holes have recessed holes and the tool I bought has threads too short to thread it on. 

I was Hoping to find out what kind of shape the engine is in to see if it warrented replacing all the lines.  Maybe I'll borrow another kit from one of the four auto parts stores near me.  She starts and runs fine, has a steady oil pressure of 50 but I need more info.

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