Hey folks,

I had a machine that I trust that has done multiple engines for me put together my bottom end for my turbo setup. Hot start the car had 65-70psi or so of idle oil pressure and did for a while. I brought the car to the dyno, and I noticed that my hot idle oil pressure dropped to 55-60 after the day on the dyno of tuning and making adjustments, no big deal that was still a great number. I drove the car all summer at 750whp and the car ran great. Hot oil pressure never came down. Then I went back to the dyno to try to break 800 mostly because I'm an idiot and THEN the oil pressure hot at idle dropped to 40 psi. Once I got home, I made 1 pass down the drag strip and the pressure dropped to 20psi. I loaded the car right on the trailer and took it home to pull it apart.

Engine setup:
Forged K2 rods
Wisco pistons
King HP rod bearings
I THINK the main bearings were a standard 2 layer bearing, but they may have been the King HP as well. I can't remember.
Stock crank
High volume oil pump (10296)
15degrees of timing at 14psi on 93 pump.

So at first, I was thinking it was going to be detonation and it had wiped a rod bearing as I am running pump gas, but it never gave me an issue on the street for a whole season, and I definitely put it through the ropes. I drained the oil and ran it through a paint filter with nothing in the oil. I cut the oil filter apart and at first glance there was nothing in that either! But as I really started spreading the element out, I started to find some evidence of bearing material, but barely. But when I've killed rod bearings before there was tons of material right in the pickup tube screen never mind the filter. Then as I was disassembling the engine, all the rod bearings looked great, but one of the rods had bearing material on the rod itself, soo then I knew it was a main bearing.

Looking at the pictures bellow, could timing have done this if the rod bearings were upgraded and the crank bearings weren't? I kind of find it hard to believe all the rod bearings are alright if it was from detonation, but they're curled in like rod bearing detonation. Maybe the high-volume oil pump is draining the bottom end during big pulls like on the dyno etc and that is what wiped the mains because the oil couldn't get back down to the pan fast enough? I was going to try a 10295 high pressure standard volume pump this time around. The first 2 pictures the bearings had fallen out of the caps when I lifted them off, so I set them back in for place holding. They're obviously backwards there but they weren't when they were installed lol. The trust bearing is just how I pulled it though. It was starting to spin!

What do you guys think?

 

Pull a bearing shell on the mains and rods. The bearing will be stamped on the back side with the manufacturer and type.
Rod bearings don't look like HP.
Lots of heat in the mains. Do you know what clearance they were set to?
And how do you know it wasn't detonating? Are you running knock sensors?
And what engine management?

 

Ahh maybe the rods aren't the HP! I just thought I remembered the machine shop saying that they went that route. It could have been something else and I don't remember though as it was a while ago. I'll see if I can find the receipt.

It certainly could have been detonation! I have no knock sensors and running the Holley HP system. Seems like most guys don't run the knock sensors with anything that's not a stock setup anymore because of tuning them. Have you seen detonation kill mains and not rods?

Lots of heat in the mains would point more to oiling than detonation anyways correct? As far as clearances I don't know, within whatever the GM spec would have been.

 

Detonation would be evident on spark plugs and piston domes…maybe even chamber if bad enough. If you never heard anything, look closely at plugs. They will not hide detonation.
But detonation usually takes out rods first as you state, and they look ok from the pictures anyway. Regarding the mains, what were the clearances set at? Do you know your oil temps? The blackening on the bearings shows that the oil was very hot. This was not a product of an oil starvation issue. If that were the case, the rods would have went away first, because they oil last. Keep the pump you have if it’s not damaged. Of course it will need a good cleaning. I’d suspect a clearance issue ALONG with an oil temp issue, being as how this is a boosted engine. An oil temp gauge is your best friend in the performance engine world.

 

Some questions to help me address your bearings:

• Was the stock crank cut, polished, or both?
• Did the machine shop note the oil clearances for the mains?
• Was the stock crank the original to the block?
• Was the block line honed on the mains?
• Did the machine shop note your crank end play?

I see evidence of a main journal that's barreled (i.e. surface is not flat, tapered from the middle to the edges) based on the wear pattern in your first photo. The #3 main certainly did get hot, and I'm unsure if that heat damaged the thrust surfaces, but it's likely. Finally, since the other mains don't show journal barrel, I can only assume either line hone wasn't done or they boogered up a cut or polish of the crank. If you can. post more photos of the bearings, front and back, and the journals on the crank.

 

I've been running a Melling 10296 since 2005, 70,000 miles. No issues. I have to believe you can rule that out. Besides, mains in the LS get oiled before the rods, and the rods are better than mains. I'm going with wrong main bearings/wrong clearances, or both..

 

Hey Grinder, it isn't helpful to quote the whole original post......

 

It does seem like its pointing towards a combination of the bearing tolerance and the thicker oil I was running being the root cause here. The machine shop who is setting up the new engine is aiming for .0025 for the rods and mains. And I'm going to go with a 10-30 oil. Now the question is to run the 296 or the 295 pump since I have both of them.

 

 

I guess I should bold this part

 

Damnit!!! I'm usually better about reading more thoroughly

 

I read where a guy smoked his motor when he purchased a plate from eBay, the one that goes above the oil filter.
The pipe thread was too deep and the fitting extended into the channel and plugged the through port for the oil.

 

Interesting! I'll have to look at this to make sure that's not happening. But I'd imagine he would have had visually low oil pressure?

 

Sorry.

 

That couldn't have happened here, or the rods would have been smoked, too. Frankly, I'm amazed the rods are in as good of condition as they are.

 

Which leads me to believe the oil pump was fine and it didnt suck the pan dry pointing to the rod tolerances being loose enough and the main tolerances being too tight for my application and the oil I was running (15-40 Rotella)

 

I'm sure the pump was fine, too. I was kinda referring to the fact that with that much trash on the mains, it would seem some of it would've gotten to the rods, but apparently not.

 

What trans and converter?

 

T56 magnum and dual disc clutch