I built a new engine for my truck and have had it running for about 4 weeks now. This is the first engine I have built entirely by myself. Its probably got around 500 miles on it. Specs: LY6 based, stock crank, Eagle H-beam rods, Wiseco pistons, P-series Clevite bearings, stock oil pump. While having the machine work done (hone, clean, balance, etc) the machinist recommended I have the crank turned/polished to the low side of the crank journal spec. I don't remember exactly what the diameter numbers are, but I'm sure somebody here knows them. I verified myself that all the journals were perfect, and no hourglass-effect was going on. Me and a buddy blueprinted the whole thing to make sure it was going to be a quality piece.

After some careful break in time, I changed the oil, probably around 100 miles or so. I ran ZDDP break in oil (I know its debatable using high zinc oil being a roller cam engine) and some GM EOS. After that went to Mobil 1 synthetic. This weekend at the track I noticed oil pressure dipping a lot lower than I was used to. It would sit between 15 and 10psi at idle, with a little fluctuation. I let it cool down for about 2 hours before I went home. Starting it up to go home oil pressure was around 30 at idle which seemed normal. I talked to a few F-body friends of mine who said their stock LS1s idled in the 50psi range and went between 70-80 when they turned the motor pretty quick. This 6.0 has never gone that high, even when it was a stock LY6. After leaving the track, oil pressure started dipping down again just as it did before. Once I got home I changed the oil out to VR1 20w50 to see if the thicker oil would do anything for it. Overall it seems to have gained about 5psi.

I got a video today of what the pressure looks like...

http://s271.photobucket.com/albums/j...t=MVI_1575.mp4
(disregard ECT, as that gauge is not currently connected)

Pictures of the contents of the oil filter before I changed the oil to the VR1.





Again, asking around, some engine builders have said this amount of debris in the oil is normal from a new engine. Seeing as the oil pressure is low, I am still concerned. I think it is worth noting that I am running a piggyback wiring harness/ECM setup, and my cluster is driven by a separate ECM than the one that I get data from in HP Tuners. They report very close to the same pressure, however they are both connected to the same signal wire from the oil pressure sensor. I'm not sure if the extra load there from the additional wire would have any effect on the sensor itself. I have considered a bad sensor/sending unit.

Any suggestions/opinions?

 

It appears you have some bearings going south either main, rod or cam bearings that fluctuating oil pressure is a good indicator of that. That material you have on the rag indicates a bearing failure and in no way is that amount of metal in the oil normal. You should have none at all or any that is visible to the naked eye.

 

What is fluctuating oil pressure an indicator of physically? As in, what actually happens to cause movement in the needle?

 

It is usually an indication of a bearing or oil pump or sending unit that is failing, with what you found in the oil pan, you have a bearing failing, the pressure will fluctuate with the viscosity and temperature of the oil. I have included a link that can give you some insight on your problem.

http://www.machinerylubrication.com/...e-bearing-wear

 

Here is another picture to get an idea of the size of the stuff on the towel

 

Did you cut open the filter when you changed the oil? If your bearings were going south there would be a lot of metal in it.

 

Yes, that is what came out of the filter.

 

Interesting thing I found yesterday... Oil pressure drops with a rise in manifold pressure, and vice versa. RPM remains the same. That leads me to believe it is a main bearing problem. Here's an HPT snapshot of it happening:

 

Bump...any ideas on this? I'd kind of like to get an idea of whats going on before I take anything apart

 

still trying to figure out why the builder wanted to turn the crank to the low side of spec and didnt foresee this happening. i would be talking to him about that to see if there was a logical reason.

 

I'm not sure, is it just more of an old school small block thing? He seemed very knowledgeable, albeit extremely opinionated, but he may have bit off more than he could chew. It got me curious about his knowledge with LS engines when he was surprised at how much the block weighed, as if he hadn't dealt with an iron block LS-series engine before. I hope it was a simple mistake of my own... I will certainly be talking to him about it if I discover a problem with the machining.

Another thing I thought I'd mention... He recommended replacing the cam bearings because there was copper showing, so I agreed and brought him the new bearings he requested. They were narrower than the stock bearings, but he said that was acceptable. They were narrow enough that they don't cover the entire cam journal. Is this correct?

 

Off topic, but here's a video of the first time to the track...

http://youtu.be/u7UElh1LKb0

Shortly after this, I noticed the pressure dropping off to the 10psi range

 

I had an experience about two years ago, with a GM head gasket wish let go of lots of the coating and formed a fur ball around the oil pick up tube screen, causing the kind of problem you have, i didn't have that size Babbitt pieces in the oil tho..

 

" the pressure will fluctuate with the viscosity and temperature of the oil."

I can vouch for this statement, in regardds to bearing failure. For some reason, my bearing appeared to be worn, but not turn. I suspect for some reason it didn't get oil like it should. It happened one day at the track after multiple instances of the car not shifting at the shift point programmed ... over revs. That got to be an expensive night for me.

Idling cold, about 40-45 PSI. Cruising with the oil hot, about 25 PSI. Idle, 8-10 PSI. Pressure varied with acceleration. No bearing noise. Engine still sounded great.

 

Pulled bearing caps 2, 3, 4...all are demolished. Haven't looked at 1 or 5 yet. None of them spun, but were certainly beaten to death.







Either there was a severe lack of lubrication or I forgot to torque -all- of the main bolts... Anyway, just updating the thread "for the record". I may end up joining the 4.8L craze while I rebuild this engine.

 

Good god man..that really sucks. Sorry to hear this, hope shes up and running soon?

 

I resisted opening up the engine since I heard no bearing noise. But, there it was: a bearing issue; not spun, but otherwise worn to the point oil leaked right past. At least now you know ... the mystery is over.

 

Mystery is somewhat over. Still trying to figure out why it happened. Here's a question for the engine builders...when you assemble an LS engine, do you scotch brite the bearing surfaces prior to installation? I had a friend help me with the build who has done many builds before, albeit old school motors, but he has used the scotch brite method on all of them and never had a problem. I ran across info today that said specifically not to do that because it will take the electroplated overlay off. Could that, coupled with an already loose bearing clearance, be the cause of the bearing failure?

 

Scotch brite the bearings? Wtf. Not trying to be a dick but u are better off buying a book on how to build ls based motors and building ur motors urself.

 

Scotchbrite. There is your answer. As you use the pad, bits and pieces break off. These will get in EVERYWHERE and act like grit and just grind everything apart. If you have the oil analyzed, they will find Scotchbrite grit in there.
I never use a scotchbrite pad anywhere close to an engine.
I'm in the plastic injection molding business and every once in a while I hear of someone "polishing" a mold face with the stuff and causing thousands of dollars worth of damages from all the scratches!
Expensive lesson. Maybe others will learn from this.