LS1 Autopsy

Hey guys,

So some of you may remember my last post documenting what appeared to be my newly rebuilt LS1 oil starving and throwing three rods at Putnam Park in Sept. Well, I finally got time to pull the bottom end completely apart and now I'm not so sure it was oil starved.

From what I understand, if it oil starved I should see lots of "rainbowing" color on the bearings, or even bearing welded to the rods/crank. Oddly though, the bearings all came apart just fine and didn't seem too bad. A few were obviously spun, but they don't look nearly as gnarly as I thought they would. A few are bronze colored but I think that's the coating from the rebuild with new bearings.

My current theory is perhaps the timing got out of whack and my knock sensors didn't do the job, causing detonation. What do you guys think?

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those bearings look terrible. the mains have worn right through the babbit layer and into the copper. the mains are a little weird, some are worn a lot more than others, its possible the block had line bore issues, were you by chance running main studs or aftermarket bolts? this could also be from how the oil is fed to the main bearings, i cant say ive ever looked at an oil circuit diagram so im not familiar with it.

im doubting detonation caused the issue, to have detonation bad to throw the rods out it would have been audible and you would feel the power loss. if your running a stock computer and it wasnt setting knock sensor circuit codes i highly doubt it was detonation. a couple ways to tell, for one, read the spark plugs. if the porcelain has small black spots (looks like pepper), thats detonation. another way it to measure the width of the upper rod bearing (the one in the rod, not the cap). detonation hammers the rod bearings flat, and as they get flat they get wider. compare the width of the bearing near each end and the middle, if the middle is more than 0.001-0.0015" wider than the ends its been hammered from detonation.

the connecting rod end thats still attached to the crank, is it floating freely or is it welded or stuck?

what im seeing i would suspect oil starvation. with road racing oil control is a big thing. some ls heads are known for holding oil in the top end, i think its the rectangle ports, but its something to be aware of. im not familiar with the swap oil pan for these cars, is there any baffling or trap doors in the pan? did the pan pickup height get checked when it was being installed? what engine oil do you run? are you running an oil cooler, and if so do you have a thermostat on it?

if the car is going to see heavy track use you may consider a dry sump, although not completely necessary. an accusump is something else to consider, they can save the day without you even knowing it.

Thanks, Sharkey. I had no idea that bronzing was also a layer underneath the top layer of bearing. In that case, this is very clearly oil starvation. Appreciate the reply. I'm still learning a lot about engine internals and building, as you can see!

JP