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Motor is a Lq4 block with Ls2 crank, compstar rods, weisco pistons. Set up for boost. So I get it in the car and am driving around (no boost) just putting some miles on it to break it in and everything seems great untill i notice on the second day i was driving it, it drops oil pressure to 12.5psi or so while cruising. So I park it and go get the trailer and haul it back home. Drop the break in oil out of it into clean jugs and let it settle overnight. Then the next day I check the bottom quart of the old oil and sure enough its full of cooper colored metallic dust and flakes. So I cut the oil filter open and same thing. I take the motor back to the builder (who has been very cooperative and helpful thru this) thinking a cam bearing walked or something. He tears into it and finds the front side of the thrust bearing ground down to nothing. He says something had to be pushing the crank forward and asked about the converter and flex plate first thing. Well all that is perfect. Nothing was in a bind. Converter is spaced to where there's about 1/8th of an inch between it and the pump. It def wasn't putting any forward pressure on the crank snout. The rear side of the thrust looks great so it just the front side where the crank has walked forward. All the rods clearances on the rods and pistons look good, nothings in a bind. The engine guy said he's only seen one other motor that the crank moved forward like this on. And that was big block Chevy that someone had pit the flex plate on backwards or something like that. So the only thing I can think of left is the block is messed up in that area maybe? The crank that came out of it originally was messed on on the thrust area. I told the guy this before I decided to use this block and he said everything looked good. Any thoughts?

Old Geezer

iTrader: (3)

https://ls1tech.com/forums/generatio...l-bs-pics.html

You guys have the same machinist??

What trans do you have bolted to this engine??

KCS

iTrader: (20)

I've only seen two things kill the thrust, either the thrust wasn't "set" when the crank went in or the converter is pushing forward on the crank.

How much thrust clearance did he have in your engine when he built it?

Secs-10

I'm not sure. I remember him saying the thrust was a little tight or something when I picked it up from him. And like the dude in that other post in the link. That builder sounds just like mine. Lol. Old school guy has built a lot of bad *** dirt track and drag motors. Bit only a handful of Ls stuff. I have a th400 trans. Running the adapter that goes in to end of the crank snout. Had this same set up on the sbe 5.3 for 2 years and no issues.

RockinWs6

Good read here http://www.4secondsflat.com/Thrust_b..._failures.html I wouldn't be too quick to point fingers.

wildcamaro

iTrader: (15)

Nice article rockin, good info

Secs-10

I wasn't pointing fingers just trying to figure out what could be the cause or if anyone else had experienced this. And this fast. Like I said there was less than 50 miles if that on it and it was never over 4500rpm. that is a good read tho thanks for the share.

01ssreda4

iTrader: (96)

I too had a thrust failure but it was in a 100k engine. New converter had been in a couple thousand miles........but I didn't point fingers. Its so hard to nail down the exact cause.

LS1MCSS

iTrader: (18)

You say the other crank that came out of that same block had the thrust messed up in the same area! That tells me there is probably something wrong with the block. If the builder knew the thrust was a little tight, he should have checked into that before he let the motor go out.

A.R. Shale Targa

iTrader: (2)

Two things....
First has this engine block been line honed ???
Secondly I remember reading a build thread by Tony Mamo where he stated
that he almost always has to loosen up the thrust by lightly sanding both
sides of both bearing shells since for some reason they are usually .001"-
.0015" which if you think about it is tighter than the bearing clearances.
I usually set it at .005"-.007" and have only ever seen a problem if the
torque converter was pushing(not shimmed right), ballooning(nitrous hit), or
an overly aggressive clutch set up on a stock car....in which case I massage
additional oiling grooves into the sides of the shells for extra lubrication.

Secs-10

I'm not sure if he line bored it or not. I took him the bare block first for him to check it over before going ahead with the build. I assume he did but I don't know for sure. I've got a billet front converter with antibalooning plate and all the goodies I don't think it ballooned especially with no boost on it. I've spent hours reading possible causes on here and yellowbullet and excessive trans pressure seems to come up a lot. I have not checked the line pressure but am def going to now. But do you think even if there was pressure pushing the converter forward that it could cause that much destruction in only 40 some break in miles?

KCS

iTrader: (20)

Yes, easily. I built a engine once that ate the thrust on the dyno. They hadn't even made any pulls, just break in and generating a base map. They decided to change the oil before making any WOT pull and pieces of the thrust literally fell out of the drain plug.

I forgot exactly what the cause was, but somehow the input shaft of the manual trans was pushing the crank forward against the thrust. Luckily my boss had been looking over my shoulder when installed the crank and got .007" thrust when I checked it.

RockinWs6

This is tough because you don't know what you started with. I'd be dam sure to at least measure the clearance and I'd want to see the crank with a little Prussian blue to check the bearing to crank surface. Probably a good idea to mod the thrust bearing for extra insurance. I've seen a lot of thrust bearing troubles in LS1 engines that were run hard, even stock.

check out this thread and the video, might be something you can do to check to be sure the trans isn't adding to this. https://ls1tech.com/forums/generatio...ilure-2-a.html

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Thanks for the help guys. I'm gonna try to find out today what the clearances were set at. I'll post up when I find out more. Is there any way I can check the pressures on the trans and comverter without having a motor hooked up to it.? Maybe pull it and take it to a tranny shop that has a dyno I guess.?

Secs-10

No real updates. Still waiting on the word from the builder. He told me he didn't get it line bored because everything mic'd out good. So he's supposed to be getting it line bored to make sure and then getting back to me. I took to main cap off the old 5.3 that was in it before this motor to check the thrust bearing. Thinking if the trans was the problem then it would be destroyed on that motor as well. And to my surprise it looks great. Not abnormally worn at all. So does this rule out the tranny?

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Thanks. I bet thats the problem. I was thinking more trans pressure. The last glorious pull the 5.3 combo made was on 26psi and thats when the bottom end let go. If it the converter ballooned it did it then. Which would explain why the thrust still looks fine on that motor. Wish I could afford to get a new PTC or so but its not happening right now. Gonna call and see how much its gonna be to get this on gone thru and go from there. Thanks again. Hopefully this damn car will get back together one of these years. Lol

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Alright. Called converter company and talked to them. Measured the converter according to his specs and it is NOT ballooned. They are running the same converter i have on their 1500whp shop car running 5.0x @14x mph with no issues. I checked all the trans cooler lines while I was in the shop and everything flowed good wasn't stopped up or anything. No sign of contact with the trans from the converter. So now what.? Still yet to hear from the engine guy to see how the line bore checked out.

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Talked to the engine guy today. Block is no good. Said its too far out on #5 where the main bearing spun? Still don't know what exactly caused it. I'm guessing one of the journals were tapered causing it to to push everything forward. Anyway now I guess I'm out all that money for block and crank and bearings and machine work and back to square one. When I think it coudve been easily avoided if he would've had the block line bored to begin with. Which I thought he was doing. So I've found a 40k mile Ly6 for $1000. That close to me. 100% complete. I'm trying to decide if I should get that motor and just throw it in and run it with the stock internals. Or if I should tear it all the way down and start over. Or if I should keep looking for a bare block and crank and start from there. I'm kinda leaning torwards running it with the stock stuff till it bends a rod or breaks a ring land then putting the good stuff in it. What do y'all think?

RockinWs6

He's not standing behind this? I would have the trans tested and if it tests ok he owes you a engine, Simple as that.

ckpitt55

iTrader: (4)

Late to the party, but I had to lap mine as well. Out of the box gave me right around 0.0015", opened it up to 0.0035". These were Clevite H's

Sorry to hear about the block, OP.