My engine has been making unflattering noises, and having gotten back my oil report, I think my fears are confirmed: bad bearings.

Here are the problem wear metals. The order of the numbers is: this last oil test at 115k, second last oil test at 96k, average from previous tests.

Al 47, 7, 7
Pb 23, 29, 9
Sn 6, 0, 0
Mg 840, 620, 15
Fe 55, 35, 35
Cr 5, 2, 2
Ni 5, 3, 3
Cu 61, 65, 82 - lower

I'm assuming the top 3-4 are bearing metals? As you can see, lead and magnesium were up even on the second last test. Everything else came up on this last test. Any other assessment based on those specific metals?

I noticed the problem about two months ago, and it hasn't worsened at a very quick pace, even ran an autocross in the meantime (I might regret that at some point).

The symptoms are that under medium load there is a quite distinct knocking sensation and sound, though not overly loud. Not detonation, but physical knocking, like journal hitting bearing. Cruising on the highway at 2k rpm with no load is quiet. Same at idle. This points me to main bearings, as I would think loose rod bearings would be knocking like hell constantly.

There is a very slight oil seep from the rear main area (hard to tell, but not enough to drip down). I've been getting a right catalyst efficiency below threshold code. Probably unrelated.

I must admit I did run the engine for a few minutes without oil about a year and a half - two years ago. I'm an idiot, I was working on something else while changing the oil, wasn't thinking, and ran the engine for a few minutes to test something. If that's what started this, I consider myself lucky for dodging the bullet this long.

Any different diagnosis than main bearings based on all this?

Anyways, my plan now is to not pull the engine, just drop the oil pan and replace the main and rod bearings. From what I've been reading, this should be doable by slightly dropping the k member, or pulling it completely. I know I might have nontrivial journal wear, but I'd like to see how long a new set of bearings would last without turning the crank. I might attempt hand-polishing the journals in place. Tips?

1. can I replace the rear main seal with the bell housing in place? Probably not a two-piece, right?

2. where can I get Calico coated bearings in stock? This is a daily driven street car, not babied, autocrossed a few times a year. I know I don't NEED the coating, but I figure it can't hurt longevity with imperfect journals. Liked them before on a turbo 4 engine build.

3. If not Calico, where can I quickly source good bearings from? I'd like to get this done next weekend.

4. Are bearing sets the same on the LS3 as previous small blocks? I haven't been able to find anything LS3 specific. The catalogs I've seen suck hard. Any suggestions for a good online catalog or specific part numbers? Just go with dealer?

4. What else do I need to have on hand for the job other than:
-main and rod bearing sets
-oil pan gasket
-oil pan rtv
-rear main seal? (probably not)
-plastigage
-torque wrench (any funky sockets?)

5. Can I reuse all the bolts I remove, especially rod bolts, or do I need some fresh ones?

6. What am I missing?

I know that's a lot of questions, but please answer as many as you can. I'm a bit pressed for time with the holidays approaching.

Thanks a lot!

Steve

 

IIWY I'd call Katech for the right bearings (rods are like GEN I but mains
are different size) You may even want to pick up their rod bolts just to
upgrade the quality. I wouldn't think yours are bad but would be very
specific to put each bolt back where it came from...thread footprint...
I don't feel you need coated bearings unless the journal wear is excess
ive but since you are not micrometer measuring...I'd just get a quality
hardened race bearing like a Federal Mogul or Clevite.
The rear main seal will probably work much better after reducing the
clearances.(crank won't be jumping around in the mains)...rod bearing
clearances are standard .002"-.003...but room temp clearances on an
aluminum block are about half that since the expansion rate of the block
when at operating temp opens things up. Lastly, oil control on a wet
sump design has issues during autocrossing/road racing. A friend of mine
Kaboomed an 08 coupe after camming it w/headers and roadracing it on
some real sticky tires....it only had 38,000 miles. He now runs a stick GS
which has a dry-sump system and his oil temps are much cooler now.

 

Al is aluminum, and I wouldn't expect that to increase from a bearing problem. Magnesium is also jumping and I don't know why.

Pb (lead) and Cu (copper) are what I would expect from bearings; your lead has jumped up but copper hasn't.

Can you call the lab that did your report and get their take on it?

 

The guy at Blackstone Labs thinks the aluminum and chrome point to piston/ring wear or detonation. I'm still hoping it's just extra scuffing from things moving around while the bearings have too much play.

I will do a compression test tomorrow and check inside the cylinders with my bore scope. Hopefully the cylinders look acceptable...

Any other tips for this job? Especially any parts I need to order?

 

Any mods on your car?

I wouldn't think that running without oil in the past, would suddenly produce the metals you are getting.

The borescope should be interesting.

If Blackstone is correct and you are suddenly getting high metals from wear or detonation, you may be looking at a complete rebuild or engine swap in the near future.
Ouch!

 

I think that running without oil in the past would have EVERYTHING to do with what you are experiencing. That episode "stressed" friction surfaces - bearings, rings, cylinder bore. Now it is declaring itself. My experience with bearing failure says it's usually either an assembly mistake or a lubrication problem. I think you may be looking at a major overhaul / short block on the horizon. Cam bearings, connecting rod bearings, and main bearings could all be affected.

 

any video/audio? Your description sounds similar to a noise I hear under medium/full throttle, yet I've been told it's the exhaust but the exhaust doesn't appear to be hitting anything. Noise just sounds like a flutter at 2k to 3k rpm under full acceleration.

 

Yup, sounds a bit like a flutter, and if you pay attention, you can probably feel it as well. Not sure if it would be distinct enough to hear on a video, but i can try to take one. If you suspect bearings, an oil test should be your first step. Try Blackstone labs. They're very knowledgeable and helpful.

If you're not due yet for an oil change, just take a sample and plug the drain back up, refill what you lost.

 

No mods really on the car. It's my daily driver with 115k. Seen its fair share of track days and autocross events. Don't baby it on the street either. But still, i would've expected this engine to last to 200k. I'm guessing the dry run didn't help.

At this point i feel like i don't have much to lose by changing main and rod bearings, and see how long i can stretch the life on this thing. If it turns out i have to do a full rebuild anyway, the cost and effort will be roughly the same whether i do it now or wait till it gets really bad. Minus this little bearing job. It's worth the risk, unless i see bad stuff in the cylinders. We'll know tomorrow.

 

well crap, my warranty runs out on 12/17. No other issues except that noise from 2-3k rpm at full throttle. No low oil pressure or anything. Thanks for the response, I'll try to get this looked at ASAP

 

Get an oil sample right away, in any small, clean, sealable container (glass jar?). If you don't get an oil sample kit in time from blackstone, try to send it to them in some other container. Definitely talk to them on the phone and see how you can get a quick enough turnaround time. My turnaround was only a few days with usps priority, but I already had the kit (container).

You might also want to talk to the dealer and see how strict they're gonna be on the 12/17 date, especially if you're bringing this to their attention ahead of time.

If the oil test comes back clean, it'll be a stone off your chest.

 

So I have bigger problems. Two cylinders have low compression - 4 and 5. 100-120psi vs 180 on all the others.

I didn't see much with the bore scope, because the spark plug angle really sucks (much easier on DOHC heads). Except #4 did show scuffing. And strangely not on the thrust side, but the only side I could see - the front, parallel to the crank.

My theory there is that as the bearings started to go, the pison/rod moved around in strange ways side to side and caused this wear (note: I had no piston wear signs in the previous oil test, only bearing wear, so pistons were presumably ok before the bearing went).

Long story short, I think in addition to the bearing sets I want to buy two sets of pistons, rings and connecting rods (I think the bushings in the rods might be shot from the weird angled loads). Take the oil pan and the heads off *without pulling the engine*. I'll hone the bad cylinders to smooth out any major gouging. Install the new parts.

If while in there I see irreparable damage, gouged journals, badly gouged cylinder walls, at that point I'll pull it and do a full rebuild. But I'd rather not. If I can, I'd like to just extend the life of this engine without serious down time. I'd like to get this done over the next two weekends.

Sound doable? Any tips? Things to not forget? Never had anything apart on this engine, so I'm not familiar with the details. I've built a turbo 4 race engine before though, so I'm not a complete newb.

Here's my list of parts, let me know if I'm forgetting any small bits that can derail the job:

-main bearing set
-main bearing cap side bolts
-rod bearing set
-plastigage
-2x stock pistons, rings, rods (wrist pins come with the pistons I hope?)
-oil pan gasket
-head gaskets
-intake manifold gaskets
-all bolts I will be taking off are reusable?(other than bearing cap side bolts)
-any gaskets I'm missing?

Thanks a lot.

 

Head bolts are not reusable.

 

sorry to hear. I got a compression test months ago when I first heard the noise and all my results were 185 with one 180. still gonna try and get the sample done. Good luck with everything.

 

If the engine has major ($$$) expensive problems, GM will want the dealer to send them a copy of the current tune/tune history, and may send a rep to actually look at it. The dealer will not be making the decisions, GM will do that. But...

If you have taken the car into the dealer with a symptom they can notice and document, then GM may pay for all/most of the repairs if it blows up next month. If you can bring in the results of the oil sample (if they show anything amiss) when you see the dealer, that's even better.

But talk to the dealer and verify your "In Service" date and warranty expiration date, get in there while still under warranty. Opening the discussion after you are out of warranty is a very long shot.