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Alright, I've been confused over this, and asking "experts" for the last week. I just finished building an LQ4 with z06 cam and gen 4 pistons and rods. It was a whole fresh rebuild. The machine shop hot tanked the block, line honed the mains, and cylinders, polished and balanced the crank for the heavier rods. They also installed ARP rod bolts, and honed the rods .001 or whatever it took to make sure the bolts didn't affect the bore. I got everything back and they gave me STD Clevite bearings for everything.
I assembled the bottom end, and verified clearances with plastigage. Rod bearings and main bearings were around .0015 to .002, pretty middle of the road service specs. I used plenty of the cheap gray lithium based moly graphite assembly lube. Once the mains were torqued to spec, the crank still spun super free. I then installed the rods and torqued to 40 ft lb. It gained a little resistance from the rings, but it definitely didn't bind or anything when spinning.
I assembled the rest of the motor, and installed it in the car, then filled with cheap conventional 5w-30 (I tried to buy straight 30w but the autoparts only had 1 qt). I disconnected the coils and cranked for a few seconds and it built 40 psi of oil pressure, then I plugged the coils back in and it fired right up and ran great, it made 55-60psi on the cold start, and then settled around 50 or so. The motor sounded and felt great as I let it warm up a couple times still on jack stands. A couple days later when I had a spare minute from homework, I dropped it down, and took it for the first drive around the block to adjust the tune for the new setup. I had noticed oil pressure was down a little but I didn't think it was an issue, it was around 35 idle, and then would come up to 45 or 50 with a little rpm. I got everything dialed in pretty good on gentle driving, and checked afrs with a little boost (like 8psi) and only like 8 degrees timing, and everything seemed great. Then I parked the car and took it out again 15 or so minutes later, then whenever I got to any reasonable rpm it would pick up knock and pull all of the timing out. I looked down and the oil pressure was down to 15 or 20psi so I parked it, and checked the oil and it was full of bearing material.
I pulled it back apart after only 20 or 30 minutes and less than 10 miles on the engine, and I find mains #2,3,4 all severely damaged and cracked. They also shrunk from the heat. The rear thrust face of bearing 3 was also pretty scored up but didn't look nearly as bad as 2 and 4. Rod bearings 2,3 and 7 also took a lot of damage and shrunk down.
I have been searching, and talking to several people about this, and I keep hearing different suggestions, none of which make a lot of sense to me. One of my initial speculations was that the th400 I built had excessively high converter charge pressure, It was the first automatic I had ever built by myself, and I was like 17 when I built it, but I ran it on a trans dyno and checked all the pressures as it went through all the gears and everything was about where I expected it (typically high pressure from the stiffer reg spring that came with the transgo shift kit), I don't remember how much exactly, it was a few years ago. I also considered potential issues with the jegs HD converter I have, but it isn't ballooned, and I just struggle to believe that it could have pushed hard enough to wipe out the thrust bearing and burn the hell out of the other mains. The damage really looks to me like oil starvation, but I just spent an hour and a half inspecting all of the oil passages and there absolutely is no restriction anywhere. My other thoughts include possibly bent crank, but I'll be pretty disappointed if my machinist polished and balanced my crank and didn't catch that it was bent. (and it definitely wasn't far off if it is bent because it spun really free). But I plan to take the crank and block back to have those rechecked.
A couple other things to note, and things I've checked. There was clearance between pickup and oil pan bottom. The front oil plug is there, and the rear barbell was there and sealing well. The oil pickup oring was definitely not pinched, the pump is a new melling OE replacement. and this might be unrelated, but the new front crank seal was leaking a little, but it was a stupid pro comp seal, so it could just be because the was junk, or from torching the crank pulley to install it, haha.
I am just posting a ton of pictures, unfortunately I don't have many good pictures of the mains because my dad took them to show the machinist who builds his motors. rear thrust face forward thrust face rod #2 rod 7 I believe a better rod rod journals 3 and 4 main #4 main #4, #2 looks about the same
Main journal 3 and scarred thrust face rod #3 I think
Did you fill the pump with oil and spin it by hand before install?
Bypass valve and spring in place?
Nothing left in side the motor right? <wink> Who could do that? (Shop rags.. happens way too often.. )
Oil Filter boss correct? I had a guy install a dry sump boss once on a regular V8 turns out it didn't let any oil through with you use a filter..
Main Bearings all in with holes matching?
I never use graphite or heavy grease in engines, just use real for purpose engine assembly lube.
- I like redline or lubrimoly or Victor or if I can find it Lycoming.. In a pinch I use 50Wt racing oil and soak all the bearings in it before assembling them.
I use a internal and external micrometer to check the Rod/Main/Cam bearings,
Plastigage works but I've had it over compress while torquing and it makes the tolerances look tighter than
they are. I rent the mike and snap gauge so I get a nice clean calibrated unit of rthe once in a while that I go that deep in the motor.
It's all so smoked that it's hard to tell what happened first.
Did a motor blow up in that block before you built it?
If so, did YOU PERSONALLY run a rifle brush through EVERY SINGLE oil passage along with plenty of hot soapy water and diesel fuel, to clear the metal chips out of it?
If not, then that's why it's like that now, and why it will most likely happen again if you don't do that.
The motor ran fine before I tore it down, and all the bearings looked great, before I assembled it, everything was hot tanked and clear. It had the correct o-ring. While the engine was upside down, I poured a little 30w in the pickup tube and turned it over to at least fill the pump. The oil filter boss is the same stock ls1 part that was on the 5.3 last week, so that was all good. And the lithium based assembly lube is specific assembly lube from the auto parts. I haven't taken apart the oil pump, but I figured it should be fine, because it made plenty of pressure initially, but I can pull it apart and see if anything seems off.
Also, I cleaned the hell out of the whole engine, everything was hot tanked and then the day I assembled it, I used like 6 cans of brake clean before assembly.
Sounds like a nickel part got you some where.. I hate it when that happens..
I remember back when forgetting the oil pump drive shaft was the big zinger,, but that wouldn't apply here..
I'd go ahead and tear the pump apart, since it will need it anyway with all the bearing shrapnel in the motor..
Make sure the bypass piston and spring are moving and springing..
I'll tear that down tonight, just to be sure, I am going to reinstall the crank on the outer mains with bearings and check for any bending in the crank, and I'll remount the flex-plate and bolt it to the converter and trans to make certain it wasn't pushing or anything. Thanks for the help! I'll update if I make any progress
I'm betting on something login sideways in the oiling system, and it has to be between the pump and the mains..
Hmm dogbone, relief plunger, or the oil pump gears are loose enough it may have needed a full pressure prime..
I have also seen a case where one main didn't lube, stuck, spun, jammed the crank and spun the rest, but that was on a OLD antique V8.. not sure a LS could even do that..
Also once saw a motor die like this because the builder put the wrong plug in an oil gallery hole and it acted like a valve shutting off oil flow to the crank, and the pressure looked fine because it was still pumping to the top end. Which was dripping just enough oil to keep the mains and rods alive for a few minutes at idle, under power everything borked..
Here are the mains in order, if that helps. I would also like to know if anyone would argue that this problem stemmed from the converter pushing the thrust bearing. My machinist is dead set that this is all secondary damage caused by the thrust bearing getting torn up. Even though the thrust face took minimal damage compared to the rest.
Thrust clearance was in spec when I started, I know I checked but I'm not remembering. Now I just measures .015 after all the damage. BUT I just checked my crank run out with the crank bolted with the 1 and 5 caps torqued. I measured a full .003" run out on mains 2 3 and 4. and measuring on the snout I got .005" and I put the bottom half of the thrust bearing in and put assembly lube on it, and I can watch the clearance close and open as it wiped the lube off the the crank. So I am searching for acceptable run out and I am finding people saying that a few thousands is ok. This doesn't make any sense to me though, because factory bearing clearance is .0008-.0025. Do they actually mean a few TEN thousandths? I am running stock clearances so my run out basically covers my entire bearing clearance. It is a little weird because the crank still spins smooth, but I can actually hear it barely scratch up against the center bearing as I rotate it slowly.
Am I confused, or is this definitely my issue? and if so, would you assume that the crank just got too hot while he was welding on the counterweights for balance?
Looks like the 3 middle lower mains took the biggest hit. And the thrust bearing IS the middle of the worst ones. Can't see the thrust faces, though.
These are the thrust faces again, I measured with calipers, and assuming my caliper is accurate and that the sides on a standard bearing start as the same thickness, then it took .005 off of the rear face.
Also, these are links to short videos of my crankshaft measurements, does anyone want to check them out to verify my readings are accurate?
To be clear, you are re-checking this on new bearings? Were the original bearings coated?
This is a FI setup. Turbo?
That is rechecking on the old 1 and 5 bearings that took minimal visible damage. I recognize that this could alter my results slightly, and I won't make any final calls without having the machine shop verify my readings. And these are just standard uncoated clevite P bearings, I am not sure why my machinist ordered Ps and not Hs, but I'll be going H next time.
Yes single turbo in a 2000 z28. I guess I should have made that more clear. But I should be clear that I am quite confident it was losing bearings long before it ever saw any boost.
I agree with your builders. Looks like a converter/trans issue.
Thanks for the response! So if that .003 and .005 run out is accurate, you would say that isn't an issue? Would you suggest that the bearing could safely take that load and flex the crank back?
Also, last night I bolted everything back together and clearance was great, between the trans pump, and the converter, and the converter snout still has plenty of clearance to flex forward before touching the crank. So if it is a trans/converter issue it would have to be excessive converter charge pressure, and I know that there is no restriction in the cooler or lines, so the excessive charge pressure would have to be a result of the heavier regulator spring provided in the basic kit by transgo. I am planning to call them today and get some pressure information, then I can make a few calculations to see how hard it could possibly push (assuming). Because there is only a small amount of forward projected area that can actually turn the pressure into a net force.
And do you think that just the small amount of thrust bearing material in the oil would have been enough to destroy the nearby bearings, even worse that the trust bearing itself? And why would the 2 and 4 bearings have gotten so hot while 3 didn't (at least not enough to warp, crack, or melt it)? I was starting to think that the thrust bearing took damage primarily because it was the surface that was subject to the most material as the radial surface of the bearing was coming apart.
Thanks for the response! So if that .003 and .005 run out is accurate, you would say that isn't an issue? Would you suggest that the bearing could safely take that load and flex the crank back?
Also, last night I bolted everything back together and clearance was great, between the trans pump, and the converter, and the converter snout still has plenty of clearance to flex forward before touching the crank. So if it is a trans/converter issue it would have to be excessive converter charge pressure, and I know that there is no restriction in the cooler or lines, so the excessive charge pressure would have to be a result of the heavier regulator spring provided in the basic kit by transgo. I am planning to call them today and get some pressure information, then I can make a few calculations to see how hard it could possibly push (assuming). Because there is only a small amount of forward projected area that can actually turn the pressure into a net force.
And do you think that just the small amount of thrust bearing material in the oil would have been enough to destroy the nearby bearings, even worse that the trust bearing itself? And why would the 2 and 4 bearings have gotten so hot while 3 didn't (at least not enough to warp, crack, or melt it)? I was starting to think that the thrust bearing took damage primarily because it was the surface that was subject to the most material as the radial surface of the bearing was coming apart.
Was the runout measured before or after this happened? When I’ve seen the trust damaged like that, it will usually bend the crank a little, but nothing more than what a good crank grinder can straighten out. I’m probably not much help in diagnosing the problem, but on three separate cases I’ve seen this happen, the cause was always behind the flexplate or flywheel. After corrections were made, the problem went away.
it’s common, at least in my experience, that the two mains nearest to the thrust get torn up like that. I think it has to do with the crank flexing. The rest of the bearings certainly could have been damaged by the debris from the center mains. It’s like a chain reaction as a little bit of bearing material can damge the other bearings downstream in the oil supply and cause more debris.
Was the runout measured before or after this happened? When I’ve seen the trust damaged like that, it will usually bend the crank a little, but nothing more than what a good crank grinder can straighten out. I’m probably not much help in diagnosing the problem, but on three separate cases I’ve seen this happen, the cause was always behind the flexplate or flywheel. After corrections were made, the problem went away.
it’s common, at least in my experience, that the two mains nearest to the thrust get torn up like that. I think it has to do with the crank flexing. The rest of the bearings certainly could have been damaged by the debris from the center mains. It’s like a chain reaction as a little bit of bearing material can damge the other bearings downstream in the oil supply and cause more debris.
The measurements were taken after the damage. And I will put some more thought into that, I appreciate the help! I just really hope I can figure out the problem and fix it right, without wasting too much money replacing good parts. I have been very careful to build the car on a TIGHT budget, because I am a broke mechanical engineering student and the car it is built mostly with scholarship funds, haha, and I definitely can't afford to go through this again.
09-18-2018, 11:57 PM
Fresh Rebuilt Engine Destroyed Several Bearings?? 
