actually compression ratio and cylinder compression dont really have anything to do with each other. just like tinman was saying, you can have a really high compression ratio and no cylinder compression. it just shows how well the cylinder can hold the pressure (rings and so on). with a high horsepower engine built to a race type of spec, they use low friction rings. they can get away with using this because they end up tearing down the engines so often anyway. one of my teachers (hot rod teacher actually) is part of the chicago-wise-guys and has lots of toys. he was telling us that one of his cars was lucky to hold about 80 psi in it. not sure what the compression was on it though, but i can tell you that it was a 6 sec car.

 

You wouldn't have to rebuild it with that compression. I mean that isnt great but it would still probably last at least a year. Stock compression is supposed to be 8.5:1, and in the cylinders a new 5 liter engine is supposed have around 175. Probably a little lower than that. Although on a 83 i wouldnt be suprised if the ratio is 8:1 and in the cylinder it is 150 new. My numbers are off 87-95. Either way you should be fine.

 

I did a compression test on my 82 and it was 130-135.

 

Well we are going to rebuild it anyways, we dont want a motor that will last a year, we want one that will last for years.