How long before rebuilt engine rings seat? EDIT. Help a 1st time engine builder.

[brianao34]

5% or less on a fresh rebuild is what you should see. 10-15% is what you should see on a used engine that doesn't have excessive wear and would be barely acceptable on fresh rebuild. The 30% number means something is seriously wrong.

Great, thanks.

[jlevie]

So, I did a leakdown test last night and:

1:5%
2:10%
3:10%
4:30%
5:15%
6:10%

Should I be seeing single digit numbers on a fresh rebuild? or is 10-15% good?
I'm going to re test it tonight when I get home, I think the cylinders had a little oil in them I believe.

5% or less on a fresh rebuild is what you should see. 10-15% is what you should see on a used engine that doesn't have excessive wear and would be barely acceptable on fresh rebuild. The 30% number means something is seriously wrong.

[brianao34]

Just talked to Frank at Deve's Piston rings (where I got the rings)
He said because my compression numbers were so high and consistent and that it doesn't smoke at idle that he'd bet its the valve guides/seals.

Going to re-leak test and go from there.

There's hope yet!

Also asked him about using the Marvel Mystery Oil and he said that shouldn't have been a problem.

I'm really thinking it's something in the head considering the car pulls HARD, just smokes.

[brianao34]

So, I did a leakdown test last night and:

1:5%
2:10%
3:10%
4:30%
5:15%
6:10%

Should I be seeing single digit numbers on a fresh rebuild? or is 10-15% good?
I'm going to re test it tonight when I get home, I think the cylinders had a little oil in them I believe.

[nando]

...and I'm a big fan of the 'warm it up, and get on it' method.

Done 5 or 6 engines that way, and they always seal well. Better than the constant idle...
...and the cam doesn't mind, as long as it doesn't idle below Jim's 2500 or so.

If yours is still burning oil at 120 miles, warm it up and do a series of 6k pulls
at wide- open throttle, with a 'lift and coast' with closed throttle.

What I've found, on everything from M20's to G72's...

t

this is what I do as well. warm it up, then drive it like you stole it. the only real no-no is extended time at high RPM (like trying to top out a car powered by an M20).

[TobyB]

Burned 5 quarts of oil today driving hard for around 75 miles.

You have a more serious problem, then. Even a poorly- seated set of rings
won't burn THAT much.

Sorry.

And every set of rings I've used have said to use motor oil as an assembly lube.

Yep, no synthetic first load. But DO use a break- in oil from a reputable distillery...er....

t

[BlackbirdM3]

It took me a good 300 miles on my Datsun engine the first time I rebuilt it. I was also using Deves rings at the time. I knew exactly when the rings seated because the sound of the motor changed slightly and it started pulling like a freight train. If I remember correctly, the oil consumption was a bit on the high side till that point. I was also keeping the revs below 4k rpm, and didn't go above that till 500 miles, adding 1000 rpm for every 100 miles after that. I thrashed on that motor and never had an issue. I think that build was better than the current one I did 2 years ago.

Never use a synthetic oil for the first 3000 miles. I've been told that by various machinists and engine builders who know far more than I do.

Will

[tinkerputzer]

The one peice oil control ring is pretty hard to screw up (unless it is gapped wrong) vs the three peice which has an expander ring that can easily be screwed up.

[brianao34]

Oil control ring probably isn't the problem then.

Do you mind explaining your train of thought for that?

[tinkerputzer]

Oil control ring probably isn't the problem then.

[brianao34]

I think you are correct in that the mystery oil added in the cylinders is the reason. Most BMW engines require the rings to be installed dry into a dry cylinder wall.

FUUUUUUUUUUUUU

:(

Yea, it's little facts like that that you never know about until afterwards. Ha...

That kind of oil consumption is not from a rings failing to seat but most likely oil contol ring installation problems. What kind of oil control ring set did you use?

It was a one piece design from Deve's.

[tinkerputzer]

That kind of oil consumption is not from a rings failing to seat but most likely oil contol ring installation problems. What kind of oil control ring set did you use?

[Dj Buttchug]

I think you are correct in that the mystery oil added in the cylinders is the reason. Most BMW engines require the rings to be installed dry into a dry cylinder wall.

FUUUUUUUUUUUUU

:(

[brianao34]

a new engine built correctly shouldnt smoke at all... OP who did the work? You? Post your measurements maybe?

I did the build, it's my first build so I expected something to go wrong, hated that it had to be the rings though...
I don't have measurements anymore, but I followed the TIS religiously. Made sure I clocked the rings, triple checked the ring gap, made sure they weren't upside down, etc.
I used WD-40 during assembly to keep rust off the cylinder walls. And at some point I put a little Marvel Mystery Oil in the spark plugs holes when the engine was complete because it sat for 4-5 months before I could put it in. That may have done me in.

I'd like to hear more on this comet thing if that might actually work on a modern engine. Burned 5 quarts of oil today driving hard for around 75 miles.

I'll be doing a leak down test tomorrow.

Compression tested today and it was 200-210 across the board, but I don't know how accurate that is considering each piston looked like it might be a little wet from oil. Smh

[Dj Buttchug]

a new engine built correctly shouldnt smoke at all... OP who did the work? You? Post your measurements maybe?