Compression Test

[Guest sintid58]

I received the engine I purchased for my 55 yesterday and put it on an engine stand. I tried to do a compression test after pulling all the spark plugs out by turning the engine over with a large breaker bar. Is it possible to get a good compression reading doing this. If so the motor has pretty low readings. I did bring one up by putting some oil in the cylinder and I am wondering if the rings may be stuck. I supposed I will have to pull it apart and look at it maybe just take the parts from both motors and make one good one.

[Aaron65]

I don't think you'll get it spinning fast enough to get a good reading. You could probably just use a battery to get the starter spinning for 5 revolutions if there is a battery, making sure the engine is blocked up safely.

[Guest brh]

I don't think you'll get it spinning fast enough to get a good reading. You could probably just use a battery to get the starter spinning for 5 revolutions if there is a battery, making sure the engine is blocked up safely.

+1

Before tearing it down, since you are this far into it, why don't you do a leakdown test on it?? This will let you know exactly what kind of shape the valves, rings, and head gasket are in. Just a thought.

[Guest sintid58]

I put the starter on it and got it to spin. All cylinders are over 90 PSI. Drivers side front to rear 100-120-110-95 Passenger side front to rear 100-95-100-120. Last night I put some penetrating oil into each cylinder and after the initial time I checked I put a couple squirts of oil in each cylinder and spun the motor with the start for about 30 seconds and then I ran it again. The readings I got the last time are above and the improved some from the intitial test. I think that after it runs for awhile it should get better overall. I had thought about doing a leak down test and will probably do one. I just haven't had time to do much with it lately.

[old-tank]

Sid

Is that new engine a 264 or a 322? If a 264 the readings are excellent, but if it is a 322 the readings are low.

Willie

[MrEarl]

It's a 264 with about 50K miles that I turned him onto and have been holding my breath ever since, hoping I didn't turn him onto a POC. So sounds like it maybe a good one? Willy, what is a good compression reading on a 322. I thought 100 was OK.

[old-tank]

Lamar

The compression in my untouched original Century and the CVT engine that was rebuilt using original pistons is 150-170. My driver that was rebuilt with Egge pistons is ~120. Egge pistons are a compromise to work in 54-55-56...knowing that I would try to find nos or nors from the period. I have a set of nors sealed power pistons that when attached to the same wrist pin with a Egge piston has at least a 1/8 higher dome. The 264 in the truck is 120.

Willie

[Lapham3]

I also think compression will likely improve after some run time-that's what I have generally seen. When they are a bit low, but even, after sitting for some time, I wouldn't panic-good luck with it.

[Guest sintid58]

Yes it is a 264 and I thought the readings were pretty good, another big thank you to Mr Earl.