How much is "normal" compression??

[1just4don]

That motor I was dealing with had a compression test --

INNER 2 cylinders (3&4) were about 88

Next two cylinders next on each end from the centers(like 2 and 5) were 90 and 95.

Outside no. 1 and 6 were 100 plus.

My first question is how much is 'normal' and how much at what pressure is it time for an overhaul??

Second question --is it 'normal for the center cylinders to be 15#s or so less than the outside cylinders and that pattern?? Almost seems maybe the head isnt torqued right in the middle OR am I imagining things again??

The 'story' is this motor was overhauled and then only run 100-200 miles before being removed to get the V8 treatment. Does that sound 'plausible' as to this motor based on compression tests??

Guess I am wondering which way to 'lean' and I have to let this poor guy know what I am thinking,,,what AM I thinking??? --don--

[55 Fargo]

Those numbers are indicative of an engine with some time on her. Having a variation of I believe 15 % is okay, so your in that now. My concern would be, the inner or #3 and 4, are quite low as compared to the rest, then 2 and 5 at 95, then 1 and 6 are 100. 100 on all cyls would be good, mine were after not being run for several years, 100 to 110, with cyl #5 at 98, but the rest were from 100 to 110.

Did you do the test on a cold engine, or a warm engine, do you also do a wet test, by squirting some oil inot each cyl and observing the difference if any.

You probably alreay know this, if the test numbers come up on a wet test, it's likely rings, if not,it is poorly sealing valves.

With these numbers, you may have a leaking head gasket also.........Fred

[1just4don]

The motor is in Georgia,,I am in Nebraska. The guy selling it is doing the test. Thats the one on the HAMB that was posted here the other day. I am ONLY guessing but for sure it was on the shop floor,not in a car,,,so assuming cold. Also assume he didnt squirt oil in it, just dry cranked her and read the gauge. I will ask him to squirt some skunk pee in there and try tommorrow. Also try the oil deal,thanks. I am NOT sure how long its been out, on the floor and NOT run either,,,I will check. Thanks, -don-

[Don Coatney]

This might help