oldsmobum

So I finally did a compression test on the olds today... Its a 1955 324. I did the test at operating temperature with all the plugs out, dry and wet. Readings are listed dry, then wet.

1- 140, 170
3- 140, 160
5- 150, 165
7- 145, 165

2- 130, 140
4- 140, 155
6- 140, 160
8- 150, 155

Not sure what the optimal reading would be... There was no reference in the service manual that I could find. Do these readings look okay to you guys?

Rickman48

I seem to remember all cylinders within 20 - 30 PSI is acceptable.
Too many variables to publish 'optimal' numbers!

oldsmobum

If that is the case I won't worry about it... The numbers are more inconsistent than I was hoping for. By optimal I just meant within tolerance... Some service manuals give a spec for it... I was surprised not to find one in mine. Thank you for the reply

J-(Chicago)

I'm not sure if this helps you any, but my 86 305 chevy read 170-180 dry., and my olds reads around 190 dry. both are around 9-9.2:1 compression.

MDchanic

Your biggest spread dry was 130 to 150, which isn't bad, but is probably a bit more than ideal.

I'm a bit concerned that all of the cylinders came up as much as they did with oil, and that the amount they came up varied so much - 5 to 30 psi - I wonder whether your rings are a bit worn. If you know that they are already, then this just confirms it.

I'd say it looks like an engine you shouldn't worry about, but one that would gain a few HP from a set or rings and a hone, or an actual rebore.

How much oil does it use? If not much, then don't think about it again.

- Eric

rustyroger

I concur with Eric, your engine is worn, but not worn out.
If it runs ok and doesn't use excessive amounts of oil I'd leave it alone.

Dont forget engines of that vintage used to use oil even when new, back in the day when you filled up with gas the attendants would open the hood and check your oil and water levels, and the tires as well.

Roger.

Tedd Thompson

X2. Most of us with 324's would love to have those numbers. I would just run it unless it has other issues....Tedd

redoldsman

I agree with Tedd. I would add a can of Restore at the next oil change and keep driving it. I think the engine has lots of miles left in it.

oldsmobum

Thanks guys. I know it needs at least a valve job and some lifters... I'm sure it has not had new seats for unleaded gas and there is a lot of racket which sounds like valve train noise. There is also what sounds like a rod know occasionally but that is the most concerning thing about the bottom end right now. Is it a good idea to re-ring a worn in bore? I've heard mixed opinions about that as to the effectiveness/durability of the end result. Thank you for your input guys.

rustyroger

If you are easy on the gas pedal the valve seats will take some time to wear, there have been a few well written and comprehensive discussion threads about this subject on this forum.

I would worry abour a rod knock though, a light knocking can become a rod through the side of the block very quickly.

New rings are a waste of time and money in bores with any significant wear, bores wear unevenly leaving a slightly oval bore, it might even make matters worse plus the top ring would most likely get smashed by the wear ridge.

What kind of oil pressure have you got, especially when the engine is warm?.

Roger.

oldsmobum

It is something I want to do especially because rod bearings are easy to get (Same as most pontiac v8).

I know better than to install new rings without removing the ridge on the bore... I have a ridge reamer. However if its a useless pursuit I won't worry about it after all.

I get 30-40 psi cold at idle, but only about 15 at temperature... I've heard this is normal. I usually get about 30 psi cruising. The minimum spec at idle is only 5 psi according to the service manual... Yikes! I will definitely be tearing into it if the oil pressure starts to go below the 15, which i already don't like... Thanks for the input