RCSB build
02-20-2012, 08:57 PM
#276
I've been trying to get a good diagnosis of the issue before I take the 4.8 plunge and put the 6.0 on a stand... If I could just put the engine back together how it was I would be pleased. But I won't do that until I get a firm reason for why this happened in the first place. So, here's some pictures of the bearings:
Pretty clear the crank and main bearings had some issues playing nicely. Rod bearings on the other hand, they look perfect. I've heard and had several theories of my own, and I've been able to debunk just about all of them.
1) Pickup tube o-ring pinched/old: would make sense except that oil pressure slowly fell off over the month or so that the truck was up and running. If that thing was trashed my oil pressure would have been garbage from the start. And the installation is pretty hard to mess up, at least I think so, especially with the engine on a stand. The o ring was used, but I have re used them I don't know how many times before and never had an issue. The rod bearings looking fine makes it difficult to condemn the o ring. Not enough evidence for this one...
2) Dirty oil galleys: I paid to have the machine work done on it, and also paid for the inspection and cleaning of it as well. I admit I was naive and probably should have checked the guy's work over a little more thoroughly than I did, but when you pay someone to do a job....
He wasn't one of the cheap guys, either. I can't blame this because out of the 3 main bearings I have pulled and inspected so far, they all look equally beaten. I find it hard to believe that the same exact amount of dirt got into each of the bearings and tore them up the same exact way. Not to mention, none of the dirt that may have been in there made it to the rods. I've got a hard time pointing the finger at dirt causing the issue.
3) Torque value/sequence: As per LS1 How-to and a half dozen other sources, the mains were torqued in a spiral sequence to their respective values, 15lbft>80° inner, 18lbft>53°, 18lbft side. I considered that the LS1 is an aluminum block and looked for iron block values, but found the same ones.
4) Bad oil pump: This was my first guess, but upon removing it I found nothing conclusive. I compared it to another known good 5.3 oil pump. I'm no pump expert, but the internals looked about as similar as any two separate parts could look. So that got ruled out...
5) Bent crank: When I had the crank polished, I also had the runout checked. It was about .0005" too much, around .0025, so it was straightened and the final runout was .0005" total, so well within the .002" max spec. Unless the crank bent putting down around 600rwtq, then that can be ruled out too. FWIW, my LY6 dynoed at 895tq and not a complaint from the bearings at all.
6) Bearing coating: I had a friend who is a more experienced engine builder than myself help with the build, and his practice was always to run a scotch brite pad over the bearing surface prior to installation. After doing more research I found that this is a technique used primarily on older engines like SBC, and isn't necessary on the LSx stuff. I thought that was the cause of my problem until finding the rod bearings looking great, having received the same treatment.
7) Improper oil clearance: the machinist who did the work on my block recommended that the crank be polished down to the low side of factory spec for journal diameter. The tolerance for rod and main journal diameters is +- .0005, so it was polished to the bottom of that spec...about .0005 was taken off. After blueprinting the engine, all specs were perfect. If the oil clearance was too great, I can only assume the rod journals would have suffered the same fate that the main journals did. Its also worth mentioning that my oil pressure from the beginning did seem to be a little bit low, cold idle was around 40psi and hot idle was around 30. But after seeing the TSB for 6.0 oil pressure that came out a few years back saying that pressure as low as 6psi at 1000rpm was acceptable, I was anything but worried at 30psi.
I've beaten this thing constantly for several days now and still have nothing to really put the blame on for the main bearings taking a ****. So at this point, I welcome any and all theories on it...
Pretty clear the crank and main bearings had some issues playing nicely. Rod bearings on the other hand, they look perfect. I've heard and had several theories of my own, and I've been able to debunk just about all of them.
1) Pickup tube o-ring pinched/old: would make sense except that oil pressure slowly fell off over the month or so that the truck was up and running. If that thing was trashed my oil pressure would have been garbage from the start. And the installation is pretty hard to mess up, at least I think so, especially with the engine on a stand. The o ring was used, but I have re used them I don't know how many times before and never had an issue. The rod bearings looking fine makes it difficult to condemn the o ring. Not enough evidence for this one...
2) Dirty oil galleys: I paid to have the machine work done on it, and also paid for the inspection and cleaning of it as well. I admit I was naive and probably should have checked the guy's work over a little more thoroughly than I did, but when you pay someone to do a job....
He wasn't one of the cheap guys, either. I can't blame this because out of the 3 main bearings I have pulled and inspected so far, they all look equally beaten. I find it hard to believe that the same exact amount of dirt got into each of the bearings and tore them up the same exact way. Not to mention, none of the dirt that may have been in there made it to the rods. I've got a hard time pointing the finger at dirt causing the issue.3) Torque value/sequence: As per LS1 How-to and a half dozen other sources, the mains were torqued in a spiral sequence to their respective values, 15lbft>80° inner, 18lbft>53°, 18lbft side. I considered that the LS1 is an aluminum block and looked for iron block values, but found the same ones.
4) Bad oil pump: This was my first guess, but upon removing it I found nothing conclusive. I compared it to another known good 5.3 oil pump. I'm no pump expert, but the internals looked about as similar as any two separate parts could look. So that got ruled out...
5) Bent crank: When I had the crank polished, I also had the runout checked. It was about .0005" too much, around .0025, so it was straightened and the final runout was .0005" total, so well within the .002" max spec. Unless the crank bent putting down around 600rwtq, then that can be ruled out too. FWIW, my LY6 dynoed at 895tq and not a complaint from the bearings at all.
6) Bearing coating: I had a friend who is a more experienced engine builder than myself help with the build, and his practice was always to run a scotch brite pad over the bearing surface prior to installation. After doing more research I found that this is a technique used primarily on older engines like SBC, and isn't necessary on the LSx stuff. I thought that was the cause of my problem until finding the rod bearings looking great, having received the same treatment.
7) Improper oil clearance: the machinist who did the work on my block recommended that the crank be polished down to the low side of factory spec for journal diameter. The tolerance for rod and main journal diameters is +- .0005, so it was polished to the bottom of that spec...about .0005 was taken off. After blueprinting the engine, all specs were perfect. If the oil clearance was too great, I can only assume the rod journals would have suffered the same fate that the main journals did. Its also worth mentioning that my oil pressure from the beginning did seem to be a little bit low, cold idle was around 40psi and hot idle was around 30. But after seeing the TSB for 6.0 oil pressure that came out a few years back saying that pressure as low as 6psi at 1000rpm was acceptable, I was anything but worried at 30psi.
I've beaten this thing constantly for several days now and still have nothing to really put the blame on for the main bearings taking a ****. So at this point, I welcome any and all theories on it...
02-20-2012, 11:39 PM
#279
How much clearance between converter and flexplate when installed?Did you spin converter to check if it was to tight before installing converter bolts?Looks like thrust side of main thrust bearing was showing wear which would lead me to think crank was thrusting back and forth.Just throwing it out there to help you rule out everything you can.Good luck getting it figured out.