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I built and tuned this LS3 for my buddies 70 Cutlass.
Was supposed to be a cruiser. It had a TH400, 2400 stall and 2.73 gears.
Well, it ran fine, but he wanted 11's. So in went a 3.55 12 bolt and he bought a cheezy $275 Jegs 3000 stall converter. Stalled closer to 3800.
After it went 11.60's.......then the oil pressure dropped. All the time he isn't mentioning this until it was idling hot at 10psi.
So cut the filter, completely plugged. To the point it collapsed internally and wasn't filtering at all.
Pressure came back mostly with oil and filter change. But still not right.
So I had him do two things. Compression check, it was all good. Then check for crank movement......oops! nearly 1/8" Thunk, thunk when prying the crank back and forth.
There was brass and aluminum in the filter.
I set this up with .007" of end play. King bearings.
Anyway, my best guess is there was no pump mod in the TH400, and that cheap converter ballooned and took out the thrust.
I just hope the damage isn't too bad.......
Dangit Ron. Your certainly no stranger to this mess. For what it’s worth, and I might have mentioned it to you in a thrust thread a year/two ago, I have went .015 on LS thrust for big power auto builds. Worked great, but as said above, and you know yourself all too well, converter quality is king.
I feel that the LS thrust is trickier to get right vs a sbc, is because of priority main oiling. The SBC’s had better oiling at the mains than our LS stuff, and it’s a learning curve for us all, still 25 years later. 100% agree with you on ballooning in this case.
I built and tuned this LS3 for my buddies 70 Cutlass.
Was supposed to be a cruiser. It had a TH400, 2400 stall and 2.73 gears.
Well, it ran fine, but he wanted 11's. So in went a 3.55 12 bolt and he bought a cheezy $275 Jegs 3000 stall converter. Stalled closer to 3800.
After it went 11.60's.......then the oil pressure dropped. All the time he isn't mentioning this until it was idling hot at 10psi.
So cut the filter, completely plugged. To the point it collapsed internally and wasn't filtering at all.
Pressure came back mostly with oil and filter change. But still not right.
So I had him do two things. Compression check, it was all good. Then check for crank movement......oops! nearly 1/8" Thunk, thunk when prying the crank back and forth.
There was brass and aluminum in the filter.
I set this up with .007" of end play. King bearings.
Anyway, my best guess is there was no pump mod in the TH400, and that cheap converter ballooned and took out the thrust.
I just hope the damage isn't too bad.......
Sigh
Ron
Ron,
You may want to try and tighten up the clearance.....that number is on the large side even for thick conventional oil (20W - 50 kind of thing).
Assuming your running a thinner synthetic you should look to target .004 - .0045 (that's a couple of thou per side which is plenty)
You just want enough clearance there to make room for a film of oil on both sides of the thrust bearing.
Less clearance actually gives you more thrust capacity. At .007 you probably have some of the crank moving and driving into the thrust time and time again.
With just enough room for oil (and nothing more) the crank never moves......it just spins freely in place.
There is a technical term for this hydraulic wedge and once you open up the clearance too much that goes away. Google it and you will read what Im referring to.
Could it be the converter? Certainly it could and that's the next logical place to look but I would suggest tightening the thrust gap a touch assuming your running a thinner weight synthetic oil which is common in most LS applications.
Im sure if you asked 10 builders you would get 6 different opinions but my thinking is you don't want the crank moving fore and aft at all.
Tightening up the clearance leaves just enough room for oil on both sides so the crank spins freely but you eliminate any hammering action (even if it starts at just a few thou) that can start working on the bearing.
That's the way its always made sense to me when I have spent far too much time sweating clearances on the motors I have built.....but as they say, your mileage may vary.....LOL
Well, it’s apart and it’s not good. It blued the crank. Thrust destroyed of course. Unfortunately the thrust bearing spun in the block. Maybe a turn or two.
My guess here is that the converter hub to crank spacer that is typically used was bound up from the get go, constantly pushing on the thrust. That’s a tricky area if you aren’t familiar with the required spacing.
Hey, Ron. You may remember my situation, where the entire drivetrain got really hot, cruising over 750 miles in one day at 120° ambient temps, which wiped out the thrust bearing? Anyway, and I don't know if this fixture is still available, but at one time, Kurt Urban Performance had some sort of jig or fixture that allowed precision drilling into the main oil galley from the thrust main saddle. This allowed pressurized oil to feed directly to the thrust bearing. I'm going to look into it, if I live long enough to pull my motor out again, LOL!! If you want to look him up, last I knew Kurt was at Scoggin Dickey, building motors, of course. Converter sounds like it ballooned, I agree. I've had a Yank in my A4 since 2005, 70,000 miles, all good. A shame this happened. Could modern tig or mig welding, and remachining, possibly save the crank? Or is a thicker than stock thrust bearing available? Hope you get him straightened out.......
Hey Grinder,
Corvettes are just way different with the trans in the back. Correct on the procedure for the pinch bolt, getting everything hot before tightening that.
Pit a TH400 on the back of the block, adapters, cheap converter and the whimpy LS thrust, you get issues.
On the turbo stuff I help with, we add a bevel to the thrust mating surfaces that feeds a little extra oil to that surface. Old school trick. Not quite as fancy as what you mentioned.
I was told never use the metal sleeve type adapter which I was pretty sure was junk before I asked. I seen where a guy used one and it was a little long, the converter slipped in it fine but it didn't allow for enough clearance between the converter and flywheel and it wiped out the thrust, guy didn't check clearance. I bought a new sfi flex plate with the bolt on spacer for mine.
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Another Thrust bites the Dust 
know exactly what you mean, I have to remind myself not everyone is working on a 3rd or 4th Gen LS1 or LSx Camaro or Trans Am. 