How to test compression on pulled motor (a few questions)

[Matt300ZXT]

So this guy has a 365hp 327 and th350 in his old C10 that he wants to sell, and I want a nasty small block to put in my 280Z. He wants $500 for it, says when he ran it, it never knocked or made any noises, smoked, leaked, nothing like that. Said it hasn't run in over a year and he's snagged the fuel pump and a few wires since then for another car. I'm not going to buy an older SBC like that w/o testing compression, so whether it's in or out, I want to test it.

Now if he still has a starter hooked to it and a good battery, I can test it that way, but in case his starter is toast or for whatever other reason, is there still a way to test it?

Also, will just a few drops down each cylinder from an oil squirter gun be enough to lube the cylinders so they won't get scratched up from being dry and then trying to be turned over?

Anyone have a clue on what sorta compression #s per cylinder I might be looking for on a 365hp factory motor? If I read correctly, they're supposed to be around 11:1 or something on compression. I don't know if there's some way to translate that to a psi number per cylinder or not.

[steveo]

you just have to be able to spin the crank, if a flywheel or crank hub is still attached, it's really easy.

should be able to turn it over by hand, especially if there's a flywheel on it.

pull all the plugs before doing the compression test to make it easier

i wouldn't worry about how much compression you get, what's important is that it's fairly even through all 8 cyls.

if there's a problem (burnt valve, screwed bore or ring, bad head gasket) you'll have a cylinder much lower on compression than the others

[Matt300ZXT]

Ok, didn't know if turning it over by hand would work as well since it was much slower. Thanks for the info.

[steveo]

as long as you can get it from the bottom of the compression stroke to the top with both valves closed, you're good

i personally wouldn't buy a used engine i couldn't see running (unless it's free/cheap) as compression tests don't tell you everything

it could have developed serious bearing issues, bent wrist pins, low oil pressure, de-lobed cam, and compression would still look OK

remember you can buy a rebuilt proven 350 longblock with a warranty for less than $2000 or a brand new GM longblock for not much more

[ShowNoMercy]

For 500 though, it would be pretty easy to rip it apart see if anything is shot and replace it if needed.

[steveo]

i guess now that i think of it, it's worth $500 just because a 327 that isn't cooked so bad you can't bore it out anymore is relatively rare

[Greg Norris]

are you getting the motor and trans for that price?

[Matt300ZXT]

Yep, motor and trans. Like I said he says it didn't smoke or leak when he used to drive it last, but who knows. I'd probably have to help pull it, but it shouldn't be too hard :)

[five7kid]

A compression test at anything less than cranking speed will give you inaccurate results.

Ideally, the engine should be at operating temperature when you do a compression test. If that isn't possible, cold cranking would give you a rough idea.

Turning the engine over by hand would only show an extremely bad cylinder at best.