New 331 burning oil

[Hilarius]

Hi Art and everyone else,
first of all I want to thank you all very much for your input concerning my rebuilt 331 burning oil.
I can by now exclude any compression losses via the valves or guides as I followed Arts advice and made up a device to run compressed air of about 120 PSI into the cylinders via the plug hole. There is a definite hiss in the oil pan indicating a loss between pistons and cylinder walls.
Compression, to make you remember, was 75 PSI and a bit over 100 with oil poured down the plug holes.
Now, what interests me is how long the compressed air of 120 PSI should stand, and in which time/seconds, to your experience the leakdown should take place to zero. Right now, it is down to zero in about 2 to 3 seconds meaning compression doesn't hold at all. Meaning also, that with the engine working, a lot of the burnt gases escape into the sump, fouling up the oil.
I now go with Arts opinion that there must be something wrong in all eight and that the pistons and cylinders might be mismatched rather than the walls glazed by extended idling.
Please: for how long should 120 Psi stand in a good cylinder and what would be an average leakdown rate in seconds?
Also, since I didn't disassemble and assemble the engine: can the crankshaft remain in the 331 engine when pulling the pistons and con rods for re-honing?
Thanks everyone.
Hilmar.

[Hilarius]

I want to thank all of you for the input concerning my newly overhauled oil burning 331 engine.
Most of my thanks go to G. Newcombe, 75-309, who wrote:
One of the worst things you can do to a freshly overhauled engine, it needs to be RUN.  Would not surprise me in the least if you find that your cylinder walls are glazed and will have to be honed and new rings installed.

When all other possibilities were exhausted this was exactly that what was found upon reopening the engine, glazed walls all the way down the ring travel.
A set of new rings and a re-hone eliminated the trouble and the engine now behaves as a newly overhauled one should.
A great lesson that not only I but several old car enthusiasts around me, and probably on this forum have learned.
Many thanks again Mr. Newcombe!!
Hilmar

[35-709]

Hilmar, you are most welcome.  It is most gratifying to me that I was able to help and that you took the time to write your very kind message above to me.
Geoff Newcombe

[Hilarius]

Certainly was a great pleasure writing the above!!
Hilmar.

[Jay Friedman]

Congratulations.  It's always gratifying to read of a success story in which advice from fellow participants in the forum helped to solve a major problem. 

Hilmar, how about a photo of your '52?

[Jeff Rosansky CLC #28373]

Glad you were able to get it fixed. I bet it was a hard decision to open up a fresh engine but in the end you did the right thing.
Also, thank you for the follow-up. Often times we are left hanging.
Jeff

[fishnjim]

Dilemma: deal with the guys who did the bad job, DIY, or find someone else?
Getting people that know old stuff is getting harder and will continue with time.
In the old days we'd do the bottom end on the car, but I don't know if that's possible on '52.   New rings and a hone job, check pistons.   I'm surprised it's so uniform, might well indicate a parts issue as noted.   
I'll add, if they smoke blue after sitting then clear up some, that usually indicates valve seats or guides seeping, but you're getting low compression and smoke all the time, that's bottom end.   
I'll repeat myself, it pays for the extra money to have them run on the dyno or test stand, before you pay or accept it.   

[novetti]

Was there any machining done to the bores?
Are the pistons oversized to match if machining was done?
Were the pistons and rings supplied together from the same supplier?

[Hilarius]

The cylinders of the 331 engine in question were re-bored, oversized pistons and rings installed, both from the same company.
The rebuilder is a reliable one, knowing his way about old cars and engines, and who rebuilt many engines for me in the past.
Everything worked well at the start, I just stretched the idle runs of the fresh engine to an extent when, what Geoff Newcombe wrote, happened, and "glazing" set in. Not the fault of the rebuilder but my own. Unknowing!!
A little honing to remove the glazing and a set of rings of the same size cured the problem. Good compression, no smoke, I am happy.
Thanks to everyone for the input.
Hilmar.

[3main]

Any newly rebuilt engine should have well over 100 psi of compression even if it has only been run once.. Seems like wrong rings.. upside down rings?  I doubt every single set of rings was clocked wrong, but maybe? My 331 has not been on the road yet and has 125 all the way across the board

[35-709]

The problem with this engine has been identified and solved.  Hilmar has pretty much covered what happened and why.

[Bob Hoffmann CLC#96]

Thank you Geoff!!! I think the horse is dead also. LOL!!!

[Scot Minesinger]

Hilmar,

Again, a shop that trusts the owner to break in a new engine is unwise.  They should have broken the engine in properly and then allowed you to drive it.  You blame yourself, but I do not agree.  I repair 1960-1970 Cadillacs and I would never rely on an owner to do anything that contributes to the full essential repair.  Usually I drive them a couple hundred miles to commission them properly for even ac work.  It is understood that it is all solved and your happy, just throwing my last 2 cents in.

[Hilarius]

Scot, you are right for the people who bring you their whole cars to have the engine redone.
I just hand in the old block and the necessary parts to rebuild it and my engine man always does as good a  job as I expect it to be. I do the rest myself.
He did many engines for me to date and none failed. I do consider this failure in question my own fault, even though I didn't know what might have happened, till after it had happened. I know now, and it won't happen, again. You live and learn.
By the bye, did you really know that extended idling can result in engine failure??
I know many old car buffs, and none had ever heard of that.
I am glad to have read what Mr. Newcombe had to offer, and he was dead right and, as stated before, we all, or at least many of us, have learned something.
And that should put a lid on the topic.
Hilmar.

[Scot Minesinger]

Hilmar,

We all know different things and I pull and install engines myself too.  Certainly you are right, cannot blame the re-builder for this failure.  I did know that you have to run these engines or they will fail when new and for rebuilds. 

Back in the 1970's I lived in an affluent area where many new cars were purchased by many of my friends parents every three years, or even every year.  Several suffered engine failures after 500 miles or less due to failure to break them in properly.  They have to be run at varying higher speeds, no extended idling and no constant speeds (like 55 mph on highway with cruise on level road). 

Last engine job I did heads were off for valve work in 2014 and all on a 472 and I ran the engine 2,500 rpm for half an hour no idling after completion.  Then followed standard 500 mile break in driving procedure and replaced break in oil.  No problems 10k miles later.   I have replaced a bunch of 429, 472, and 500 timing chains (1965 thru 1976 Caddys) and I do not break them in with that simple of work, but I do run them a couple hundred miles to be sure after each job.  Usually these cars come to me with multiple tasks and I do that first so the Cadillac is not in my possession only for commissioning.

This break in driving was well known to me anyway as a teenager and it carried forward into the 1990's until software protected the engine by shifting gears, increasing idle speed, and what not to avoid constant speed unbeknownst to the driver. 

[Hilarius]

Scot,
I also knew since my teens that a new engine had to be broken in. It was a gospel in my youth and was true for every new car and engine for decades to follow.
I behaved accordingly, as you did.
The car in question here, was in such bad condition, that every component, rebuilt or not rebuilt, had to be tested extensively so that extended idling for testing purposes seemed necessary, prior to the breaking-in period which was supposed to follow.
The devastating effect of extended idling was unknown to me, and, frankly, I don't understand the "glazing" process completely, to this day, and why it obviously cannot be reversed.
Hilmar

[Scot Minesinger]

Hilmar,

I don't understand why the glazing process happens either.  Many accuse me of being way too careful.  The time lost being careful may not have been worth the time saved by avoiding doing the work twice - have no idea, but I'm happy.