1977 360 compession test need help

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fitchett

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i tested the compression today in a 1977 360 i bought couple days ago.i tested it out of vehicle on ground using battery and jumpers this is what i got i cant decide 2 just run it or pay $3000.00 for rebuild this the first engine i have ever tested any help would be appreciated.are these numbers bad or good.

passenger side rear to front looking from front
5o
135
70
140
driver side rear to front
115
140
140
115
im going to check again tommorow to be sure
 
The compression in #'s 4 and 8 are not good. Probably leaky valves but if it hasn't been run in a while, it could be a piece of crud trapped between valve and seat also. Even bad rings is not out of the question. If you're able to start it up on the ground, I'd do that and retest the compression after you've revved it a few times. If the compression is still bad, you're looking at pulling it apart to find out why. You might get away with just a valve job but since it's already out of the vehicle, I'd at least freshen the engine with new rings and bearing too if everything else looks good once you're inside.
 
Since it is adjacent cylinders, it might be a blown head gasket.
 
cudamark said:
#4 and #8 are next to each other??
Click to expand...

lol

I say do a leak down test, or even squirt a lil oil into the cylinders and see they go up a lot, if they do...its usually the rings.

those are low enough to be a burnt valve issue fo sho, ive even seen chipped exhaust valves in a slant one time give around 40psi crancking, so...
 
since im new to building engines i think im just gonna get it rebuilt and put a nice cam in it.
 
fitchett said:
since im new to building engines i think im just gonna get it rebuilt and put a nice cam in it.
Click to expand...

since ur new to engines, u better learn before you burn... 'money' that is...

find out if the heads are shot, cause if they are...then u can simply rebuild them and save lots of coin and time buy using the bottom end u have now.

Dont just throw money at it, thats for dummies.
 
So if I read this right??

passenger side rear to front looking from front
5o 8
135 6
70 4
140 2
driver side rear to front
115 7
140 5
140 3
115 1

Pull valve covers, crank engine, examine valve gear for operation

Run check again with a squirt or two of engine oil in cylinders

Jack the carb OPEN when you run the tests

You SURE your gauge is OK? Not leaking? It's not one, I dearly hope, of these?

compression_tester.jpg
 
im gonna do another test 2day after work with a squirt of oil in plug holes ill get back with results.
 
New test results

no oil with couple squirts
8/75 7/125 100 140
6/140 5/135 150 150
4/100 3/145 110 165
2/140 1/120 150 130

i see compression did go up on all cylinders would this be a decent engine to run if everything else is good.
 
A range of 100 to 165 is not very good in my book. You might luck out and have everything stablize after it's run a while but I wouldn't count on it. If it was me doing it, I'd pull it apart and freshed everything at the least and maybe rebuild it depending on what everything looks like once it's apart.
 
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