camss2002

here are my set of clevite 77 upper and lower main bearing.... the bottom #1 and #5 seem to be ok but the lower #2,3,4 are done! the uppers dont seem to bad but are showing some copper on the sides and not so much on the top of the uppers. this engine has about 1500 miles forged ls1 with a 9.0:1 compression. im boosting about 12# with about 575 whp and 600 wtq and have gone thru 2 turbos due to this problem. i was loosing oil pressure after warm up and finally took the pan down and saw this! the oil pressure never dropped below 20psi at wot and my journal bearing turbo needed at least 40psi. now i have a ball bearing turbo and replaced all the main bearing. could it have been that the 5w30 oil got to hot, starved the bearings, and just a plain simple fix of putting an oil cooler, lower engine temps and the right oil??? the crankshaft was not bent and the only thing i can think of is the block being distored... any advise??

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incbed

If I were you I would have a engine shop line bore the mains , then have your crankshaft polished,, then let the engine shop measure everything so you can order the correct bearings.

427

iTrader: (3)

That probably has some type of alignment issue. If you put the caps on the block are they still tight to push into place and remove or are they easy to slide on and off?
Was the block align honed when assembled?
Is the assembly balanced?
What did you run for vertical main clearance?
What is the part number of the bearing you used?

Kurt

camss2002

No... the caps fit in nice. I put all of them by hand without any binding. The block was align honed by a place local who do a ton of performance ls1 all the time. I have hearned very good things and recommeded by lots of performance shops. The assembly was balanced but now tha I think about it... I did add a new clutch with a new flywheel. And never had it balanced. I used to have a mcleod twin disk billet aluminum flywheel and now moved to a centerforce steel flywheel with the 12 inch dual friction clutch but it has those weights on the clutch to help balance... not that they all ways work.... Maybe?? I had .001 to .0015 on all main caps this time. I dunno what it was the first time. I did notice the caps very tight when breaking them loose this time. Maybe the over torqued them?? The bearings were clevite 77 MP3591P. Same now going on again.

427

iTrader: (3)

That bearing is a stock replacement bearing and should not be used on a forged crank, the corner radius will contact the bearing. You might want to loosen up your clearance a bit if your hurting parts, try getting closer to .002 and make sure the oil is warm before you get aggressive with it.
Good luck!

Kurt

Syclone354

iTrader: (6)

Bringing back an old thread. My motor has wiped main bearings like this for the last two seasons. I was using MS2199H mains. Two different stock cranks. 370ci. One crank was fresh from machine shop 10 under on mains, the other standard size. Once with stock oil pump, once with aftermarket melling.

I do think i may have isolated an oil shortage issue, what is the chances of it being low on oil causing this?.