Whitelightningws6

I bought my car in 2021 with what was told was an ls2. Pick it up and it’s very obvious it’s an iron block. No 2nd gear and some other things. About a year and 4600 miles later, oil pressure starts to steadily drop over 6 months until it’s idling at 8 psi hot. Replace motor with rebuilt lq9 with a cam. I kept the old motor and I’m just now going through it because I want it in my yukon. I get it apart and it still has cross-hatching in the cylinder bores, and marks from where it looks like they align-honed the crank bores. Every bearing from cam bearing to crank bearing is worn to hell except for 2 cam bearings. The other cam bearings or cracked by the look and feel. All standard sizes. Can someone give me some insight on what y’all think happened. Assembly errors, machining errors or just ***** bearings or bad luck. And what steps I need to take in order for this to be a reliable cam only motor

bthomas

iTrader: (1)

Measured the crank journals? What do they look like? Any polish left?

Whitelightningws6

There’s some visible spots but nothing I can feel with a fingernail, still a dull chrome color

Che70velle

iTrader: (6)

It’s tough to diagnose from just pictures on the internet. Knowing the bearing clearances when built, VS where they are now is a data point…cam bearings included. If I were tearing this down, I’d pay particular attention to the oil pump pickup side of the engine. Because it looks like the engine was starved for oil, I’d carefully inspect the pickup screen, pickup tube (clogs or cracks) and o-ring seal. I’d also disassemble the oil pump and inspect. I would have checked the pickup screen to pan clearance as it came apart, and taken notes. Disassembly is almost every bit as important as assembly when troubleshooting. It’s very difficult to get the engine completely apart and in a box, before figuring anything out about what went wrong.
My second thought process here is power level, and how was this used? An engine that’s used for high rpm, boost, nitrous, etc, must be designed and assembled for the intended usage. As an example here…my machinist works for Joe Gibbs as a consultant today, but previously worked in their engine shop as well. During Tony Stewart’s early years, he had a season where he lost several engines. Bearings looked a lot like yours here. It was determined that Tonys driving style required more RPM than the typical Cup driver at that time, to keep him up front. Long story short, they ended up having to set Tonys stuff…and ONLY Tonys stuff…up at .0045 mains and almost that on the rods to make it live 500 miles.
We built engines for an offshore race team in the early 90’s that ran supercharged Big Blocks. Offshore racing is one of the toughest firms of racing on parts…it’s extreme. We ended up setting the rod bearings in those engines at about .004 to make them live.
Now I’m not saying your racing this vehicle, but it’s simply a part of the equation that must be figured in, while disassembling an engine to determine failure. You’ve had an oil supply issue of some degree. I’ve seen bearings look like this also if an engine got really really hot, but it’s usually accompanied with “blackened” bearing faces from the oil super heating.

Whitelightningws6

Yeah I don’t think I was hard on it, maybe a few highway pulls a week, I’m with you though it being an oil supply issue, I’ve got a new rotating assembly I want to put in, hopefully everything on the block side is good and I can put new bearings in and check clearances with plastigauge. I’m holding that’s all it is, I’ve got a new Melling pump, pickup, and gasket set to hopefully rule out oil starvation

Che70velle

iTrader: (6)

Pickup to pan clearance needs checked, when you build back. Highway pulls are tough on a wet sump setup, especially with big power.
What Oil pan are you using?
What kind of power level are you seeing?

Whitelightningws6

Stock fbody oil pan and pickup. I’ve got no idea what power I’m at, but I’d guess 400ish at the crank. Ls3 top end and a cam that’s it. I’ll check oil pan to pickup clearance when I get to it.

SRB

I would have it line bored, but you could probably pick up another engine for what that would cost.

Old Buzzard

My first thought was what Scott said.
". If I were tearing this down, I’d pay particular attention to the oil pump pickup side of the engine".
It was run since installed with the issue.

grinder11

iTrader: (1)

I agree it looks like an oiling issue. It could be, as stated earlier, that clearances were set up on the tight side. But AFAIK, you can't choose cam bearing sizes, they're all standard. One other thing I'd like to add, and that I think you should check. It may be a long shot, but I'd carefully check the filter bypass. It's possible it could be stuck open, at least partially. Break in can produce a lot of small particles. If they're doing an end run around the filter, it certainly wont help matters. Out of curiosity, since the cam bearings are oiled before mains and rods, are the cam bearings marginally better? I agree with Scott that it's nearly impossible to diagnose from pics.