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

[efficient]

damn im worried about doing this now. but i cant turn back cus i already bought the parts.

[Raxe]

I know how you feel. Depends on your personality, but maybe it's better if you can wait a bit and take a break before tearing right back into it. These projects are supposed to be enjoyable; if it feels like a chore and you're dreading it you'll just wind up hating the car in the end, or worse yet you'll plow through it and risk making more mistakes and blowing more money.

Either way good luck with the next round.

[brianao34]

Thanks man. It's hard to laugh now.
After I got back from the test drive I just laid on the concrete on the verge of tears. I miss my creaky old car.

[butters]

No, I don't, but from the looks of things I'll be tearing this one down so I'll snap one then if I remember...

I don't remember the price but it was $150 or so.

Not bad.

I feel your pain in terms of post-rebuild struggles... it sucks now but once you get to the other side it will be well worth it and you will have learned alot. Good luck on the re- rebuild.

[brianao34]

Interesting, I wouldn't have guessed that sleeving is cost effective on these blocks. Have any pics? Just out of curiosity.

No, I don't, but from the looks of things I'll be tearing this one down so I'll snap one then if I remember...

I don't remember the price but it was $150 or so.

[butters]

The block according to the previous owner was recently rebuilt and R3v-shifted and cracked #4 cyl. I had the cyl resleeved and after some research and inspecting it it looked like he did a great job.

Interesting, I wouldn't have guessed that sleeving is cost effective on these blocks. Have any pics? Just out of curiosity.

[brianao34]

What I'd want to have known is what the piston to cylinder clearance was. I don't have any data at hand for an S50, but I'd guess it would not be all that different from an M20. Which from memory is something like .004 to .0015. It doesn't take much wear to get beyond that range.

That was my first mistake on my first build. I didn't get any hard numbers from the machinist, just, "standard size is good." As far as the bearings, I plastigage'd each one and they were all well within spec. I assume that after checking the ring end gap that would tell me that the cylinders were within spec.

Another factor could the condition of the ring grooves in the pistons. If there's wear there the rings aren't going to work right. And then there is a possibility that the rings might not be "right" for the engine. I only use OE/OEM rings and don't know anything about the various aftermarket ring sets.

What was the mileage on this engine?

Mileage was unknown. The engine was pieced together. The block according to the previous owner was recently rebuilt and R3v-shifted and cracked #4 cyl. I had the cyl resleeved and after some research and inspecting it it looked like he did a great job.

Engine work isn't "rocket science". It is really just a matter of having the data to know what the tolerance & wear limit is and having the tools to make those measurements. When it comes to having engine work done, even at a top notch shop, my philosophy is trust but verify.

One can get away with quite a bit on a street engine and have an okay result, but if you are building a race engine there is no wiggle room. BMW's engines are built pretty close to race standards and if you want to have a good result you need to equal or exceed that level of perfection.

Yea, it's not rocket science at all, but then again as a first time builder you run into things like, is the piston skirt too scored? Or, this piston ringland has a slight imperfection, can I just file it smooth or is that something that shouldn't be done? That's my problem, I have no one close to me that has done it to ask simple questions that I end up searching for hours on the internet before I see that one guy says, "it worked for me."

I've learned a lot plenty from this build to use on my next one for sure.

[jlevie]

Well I was informed from the machinist (a competent guy referenced from my buddy) that I could use standard pistons and rings because he barely had to hone the cylinders to get them round. And I rechecked the ring end gap when assembling to confirm that the standard size rings were usable.

What I'd want to have known is what the piston to cylinder clearance was. I don't have any data at hand for an S50, but I'd guess it would not be all that different from an M20. Which from memory is something like .004 to .0015. It doesn't take much wear to get beyond that range.

Another factor could the condition of the ring grooves in the pistons. If there's wear there the rings aren't going to work right. And then there is a possibility that the rings might not be "right" for the engine. I only use OE/OEM rings and don't know anything about the various aftermarket ring sets.

What was the mileage on this engine?

Yea, I would say majority of people here, if they have any experience with building engines, would only have first hand experience with the few engines they've personally built. I need someone with lots of hands, and brains

Engine work isn't "rocket science". It is really just a matter of having the data to know what the tolerance & wear limit is and having the tools to make those measurements. When it comes to having engine work done, even at a top notch shop, my philosophy is trust but verify.

One can get away with quite a bit on a street engine and have an okay result, but if you are building a race engine there is no wiggle room. BMW's engines are built pretty close to race standards and if you want to have a good result you need to equal or exceed that level of perfection.

[brianao34]

That sure does sound like rings. Were the cylinders gauged to make sure they weren't worn past the limit? Was the block cross-hatch honed?

Well I was informed from the machinist (a competent guy referenced from my buddy) that I could use standard pistons and rings because he barely had to hone the cylinders to get them round. And I rechecked the ring end gap when assembling to confirm that the standard size rings were usable.

That is probably a fair statement, but there are some folks around that more than a passing knowledge of this subject.

Yea, I would say majority of people here, if they have any experience with building engines, would only have first hand experience with the few engines they've personally built. I need someone with lots of hands, and brains

[jlevie]

- Barely smokes at idle, smokes like a train under full throttle

That sure does sound like rings. Were the cylinders gauged to make sure they weren't worn past the limit? Was the block cross-hatch honed?

I guess the people that rebuild engines all day and master mechanics aren't usually forum-goers. :/

That is probably a fair statement, but there are some folks around that more than a passing knowledge of this subject.

[brianao34]

I think the next plan of action is to pull the exhaust manifold back and see if it's all 6 cylinders burning. Spark plugs say yes.

I'm also mentally preparing myself to tear it apart again to get at the rings. The engine has 350 miles on it, will I need to take the block back to the machine shop to get it rehoned? Or can I just get one of these "glaze busters"?

[brianao34]

You must of missed my post ;)

I was ignoring all the "ring" posts. I was in denial.

So why might the rings have not seated? It seems to be warlock magic that no one really can explain.

[whodwho]

Unless I missed it, when do you notice it smokes?

You should be able to narrow it down by:
on accel - rings
on decel - stem seals
when leaving a light after idling - stem seals

5 qts of oil in 75 mi it should be smoking like a freight train if it is burning it!

Somebody put me out of my misery.

Finally finished up replacing the valve seals (my last ditch effort before tearing the pistons out)

- Barely smokes at idle, smokes like a train under full throttle
:/

You must of missed my post ;)

[brianao34]

Somebody put me out of my misery.

Finally finished up replacing the valve seals (my last ditch effort before tearing the pistons out)
And took it for a test drive last night, still smokes...
I'm not good with failure, especially when it comes to cars.

Here are the Cliffs for those not following:
- Completely rebuilt S50B30US
- Consumes approximately a quart every 10 miles
- No oil in coolant or vice versa
- Absolutely no leaks
- Compression tests good (don't remember numbers)
- Leakdown tests good (All cylinders 3-5%)
- Just replaced valve stem seals
- Barely smokes at idle, smokes like a train under full throttle
- Car pulls HARD


And here's my theories:
- There is so much oil left in the cylinders from burning so much oil that the compression and leakdown tests are skewed and the rings are really not seated
- Maybe just maybe the oil control rings are upside down. Haven't confirmed with Deve's Piston Rings yet, but I assume they have a right-side up

But it's looking like the pistons have to come out...
Sucks, hard. I just want to drive my car again (been almost a year since I pulled the M20) and I'm stuck driving my little brother's Sentra...

Any help is appreciated, usually all the east stuff like installing air filters and changing your oil is documented left and right, but the more technical stuff is hard to find. I guess the people that rebuild engines all day and master mechanics aren't usually forum-goers. :/

[brianao34]

ANd Harbor Freight is for things like hammers and pry bars,

not leakdown testers and torque wrenches!

t

Agreed, i bought that thing a long time ago while in college, the HF tester tests at 15psi...what a joke.