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Old 10-25-2010, 06:13 PM   #1
tomtom84
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Default Built motor, burned oil, tore it down. Input requested

Herein lies the tale of my built motor that has taken 10 months, and been pulled from my car 3 times.

Cracked a ringland, and decided to go with a built motor. CP pistons, manley rods, arp head studs, stock gaskets, acl bearings, ngk iridium plugs, light hone on the cylinders. Rings gapped at CP's recommened gaps, p/w clearance was within tolerance.

Upon assembly it burned oil at 1qt/ 100 miles. This was after a good breakin period of only wg boost, and engine braking equal to throttle input. It only smoked on decel/engine braking, and would start to smoke worse and worse when I would rev in neutral [FOG machine oil smoke]. I changed the breather setup, added crawford aos, and it made no change. The turbo was also inspected by FP.

Upon motor removal I noticed wet oil streaking out the exhaust port for one exhause valve. That valve's piston is also gold due to the oil burning (I assume), and all of the other pistons have mild carbon on them (the gold piston is something abnormal)
Oil had also slightly pooled behind the intake valves, but I had the entire intake blocked from any breather hose.

The car ran AWESOME this entire time, and drove great. It never had problems building boost (19psi) and a compression/leakdown test were decent. I drove it 1200 miles the first time, and 1800 the next time. The shortblock has 3000 miles on it. Oil consumption has remained constant, but if I don't engine brake it decreases the rate of burning the oil.

I currently have the heads off and am going to get a valve job, and the guides checked. The only thing I can think of is that my guides are so worn that they are causing oil to be sucked in odd places.

[disclaimer]I didn't put together the short block so I don't know exact ring gaps.



CLIFFS:
Built motor smokes on engine braking.
Broke in correctly
rings gapped correctly (assumption)
turbo is ok
wet oil dripping out of one exhaust guide and the piston was gold when the head was removed.



could this be rings? could this be the guides?
could it be some crazy turbo issue? bad valve stem seals?


thanks.


**Resolved** Bad install on oil rings.
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Last edited by tomtom84; 03-18-2011 at 10:56 AM.
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Old 10-25-2010, 07:10 PM   #2
john 1badSTI
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how many miles were on the heads?It sounds like you built a new shortblock but reused the old heads without having them gone thru,so your guides are probaly worn especially the one in the suspect cylinder.A good machine shop should catch any issues on the heads and make them like new. good luck
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Old 10-25-2010, 07:11 PM   #3
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^^^ That was part of the issue with my old motor. ^^^

It burned TONS of oil. Most of that problem ended up being worn valves guides.
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Old 10-25-2010, 07:15 PM   #4
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I recently went through two failed builds where the main symptom was extreme oil consumption. The first one didn't make it close to being broke in, the second one made 1200 miles and we had to tear it down. Finally brought it back a year later to get another block in there and when my mechanic took one of the heads apart, he noticed the valve rocked in place in the guide. Turns out the valve stems were all worn down pretty bad. We're rebuilding the heads with new valves now, I should be breaking in the new block a week from today. I'll let ya know if it fixed it. Good luck.
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Old 10-25-2010, 07:19 PM   #5
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sounds like you
A: Assembled the rings wrong, Although this sounds more severe.

or
B: The machine shop screwed up one of the new valve guides on that cylinder
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Old 10-25-2010, 08:47 PM   #6
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It's very possible the oil gaps were facing down. This allows oil to drain past and pool up. Hence burning it
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Old 10-25-2010, 10:43 PM   #7
tomtom84
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I know the possible issue about the oil rings, but that would make me think that all cylinders would have the same issue (not just one).
I also don't know if that would cause it to smoke on only engine braking. I would think it would be burning/smoking all the time.

The heads have 90k ish on them.I did have the person that built the motor break
down the heads, media blast/clean them, and check the tolerances. I was told they were fine.....

They are going to a machine shop asap and thanks for confirming that others have had head issues.
My car has had soot on the bumper for quite a while before this... makes me wonder if the guides/stems/head wear has
been an issue for many miles...


Do you all think they need a valve job and guides, or just the guides?
I'm going to have them 100 %checked out and possibly ported/polished.
I'll report back with what I find.


I appreciate the input!!!!!

Last edited by tomtom84; 10-25-2010 at 10:48 PM.
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Old 10-26-2010, 04:20 AM   #8
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Smoking on engine braking usually is worn valve seals or guides... Although not very common on Subaru engines (but man look at those old Beemer straight sixes!)...
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Old 10-28-2010, 10:47 AM   #9
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dropped the head off last night. The guy could tell at least 4 guides/valves were leaking just by a visual inspection.

thanks for the input.
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Old 10-28-2010, 10:59 AM   #10
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poor installation of valve guide SEALS??? a little angle to them and they will not seal.
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Old 10-30-2010, 04:18 PM   #11
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I was assured they were installed correctly. We shall see...
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Old 10-30-2010, 09:54 PM   #12
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How were the oil rings??
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Old 10-31-2010, 09:58 PM   #13
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Had the same issue , turned out to be bad rings
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Old 11-01-2010, 03:04 AM   #14
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by rings wrong it wouldnt be the gaps, they are so minimal it would cause oil loss by the quarts. sounds like to me you have 1 or 2 issues..

possible bad oil ring, improperly installed, could, and i say could sparingly.. lead to possible increased blow by. but when you tell us that its under no load and engine breaking it sounds like you have bad valves.

under decel the engine isnt acting as a "air pump"..which essentially an engine is. i would preform a leak down test on the heads and come back with some results for us. its never easy to diagnose cars on the net..we can only help.

personally, i would check the valve seats. and also i can tell you if you hooked up your AOS wrong, you could be sucking oil through the turbo and out your exhaust. i did this once and the smoke screen was of epic proportions.

just remember, fix one thing at a time.
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Old 11-01-2010, 12:08 PM   #15
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I have been doing the "fix one thing at a time" and that is how I have narrowed it down to the heads. My main reason for this thread is the amount of time that I spent searching rewarded me with very little information.

The cylinders look fine (no gashes) and I highly doubt the rings are letting me burn 1qt/100 miles. I'm calling my head guy today, but I suspect the issue will be in the heads. The engine braking is what made me lean towards the heads/valve stem seals/valve guides, as the motor is fine under throttle.

I had a catch can before the AOS, and the AOS was added to help with my issue.

I can't wait to get it done and dynoed!
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Old 11-01-2010, 12:23 PM   #16
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One possibility that merits checking is the location of the tang on the bottom oil rail. Verify that it was located on the bottom of the piston (towards the oil pan) and not facing up (towards the head). If it is facing up the oil ring will un-settle and it will cause oil control to be compromised.

I learned this first hand by making the mistake myself. One bank was perfect, the other bank was not.

Valve guides were in spec, and seals were brand new. Literally spun the oil ring around and the problem stopped. It would also explain the oil getting by the ring package on that one cylinder.

Check it out, it can't hurt.
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Old 11-09-2010, 02:22 PM   #17
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The guides seemed worn, but were not at the "replace" limit according to the manual. I went ahead and ordered supertech ones to replace them, I also ordered new valve stem seals just to make sure they weren't a problem.

They should be here soon.
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Old 11-10-2010, 01:21 PM   #18
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curious for your fix as mines burns under decel as well, keep us updated.
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Old 12-30-2010, 12:08 PM   #19
tomtom84
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Motor is back in the car.

I replaced the guides, stem seals with supertech parts and had a full valve job done. While the heads were apart I also had them ported.

So far the car still seems to be burning oil at the same rate, and it is randomly giving a cylinder 1 misfire CEL under very light load.

This random CEL and my oil cloud/consumption under engine braking are the only problems I have had with the motor. The car makes great power and pulls like a bat out of hell. While the motor was down I upgraded the turbo to a 3" green with an 8cm exhaust. By changing the turbo I removed any chance of the issue being with the old turbo. A Crawford AOS v2 is being used for crankcase pressure.

I'm going to drive it for a little while longer as it only has 100 miles on it so far, but I anticipate pulling it and checking out the rings within a few weeks.
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Old 12-30-2010, 12:11 PM   #20
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Quote:
Originally Posted by Uthinkso View Post
One possibility that merits checking is the location of the tang on the bottom oil rail. Verify that it was located on the bottom of the piston (towards the oil pan) and not facing up (towards the head). If it is facing up the oil ring will un-settle and it will cause oil control to be compromised.

I learned this first hand by making the mistake myself. One bank was perfect, the other bank was not.

Valve guides were in spec, and seals were brand new. Literally spun the oil ring around and the problem stopped. It would also explain the oil getting by the ring package on that one cylinder.

Check it out, it can't hurt.
Did you pull the piston.. discover this and just re-install it?

Does anyone reuse headgaskets after 200 miles... I know they are crush gaskets.. I just hate eating my $ everytime I split the block.
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Old 12-30-2010, 12:19 PM   #21
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Did you remove the PCV as per Crawford's instructions?

I have seen folks having consumption issues routing the AOS as per Crawford's instructions, with no PCV.
Ie: A couple guys plumbed the PCV back in and the oil consumption was gone.
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Old 12-30-2010, 04:16 PM   #22
tomtom84
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Yes I pulled the PCV. I bought a new one initially before I had the crawford AOS and rebuilt the heads.
I may try and stick it back in there before I pull the motor again.

thanks!
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Old 12-30-2010, 05:31 PM   #23
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After my first built my car was a SMOG machine and it ended upo been the piston rings. Since you already did the heads and that didn't fix the oil consumption i will lean tours the rings. I have been getting a missfire in cylinder one but i think that's due to a faulty injector, weak coil or even a vacuum leak. If it was the rings like it was in mine the haeder will be cover in oil.


Wil
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Old 12-30-2010, 07:40 PM   #24
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Check the ring gaps, also make sure your oil rings and scrapers are all setup right. Also make sure the rings are staggered.
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Old 12-31-2010, 10:18 AM   #25
tomtom84
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can I re-use the c clips on the wrist pins when I remove the pistons?
Will I need to re hone the block if I use the same rings, but change their orientation?

I will do whatever needs to be done to make sure it's correct.. I just don't want to miss something.
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