Unreal

Agreed with CI GS. The bearings would have to be sooooo loose it would be crazy. Its probably oil pick up or pump.

outhouse

He is only 20lbs down at idle, and there was no reason not to build this to spec so I'm suspicious of the builder and it very well may be a combination of items involved.


As far as bearings how loose are we really talking? Looser tolerance could mean quite a few things. There is no reason at all on this motor.


If it was me I would have had it apart last week, but I do understand he has a third party involved.

AFTRBRNR

Agreed, if I weren't pulling 12+ hour shifts at the hospital I would have already been elbow deep in this thing. I consulted everyone's wisdom prior to blowing what little free time I have to narrow down my focus. The builder said "looser than stock but barely" he isn't convinced this would have been the issue. Still, the problem may be multi-factorial. So, when I find time (probably next month) I will pull this thing apart myself. If they goofed the o ring they could easily conceal it.

For peace of mind to all, the car is grounded until repairs are made.

AFTRBRNR

I finally got some time off from work.

I pulled the front cover and dropped the oil pan. The o-ring condition was fine but the black o-ring was installed. Just for fun, I lubed up the thicker green o-ring and it also fit into the oil pump.

For good measure, I removed the pump and inspected the valve-relief. I cleaned out the assembly and the relief valve is, and was, able to move freely (provided it has enough force to compress the spring).

Oil pan separated into both pieces and thoroughly cleaned. No sign of damage noticed.

pmwinc

if you are replacing the o-ring, add the Melling HV, HP pump as well M296/10296 as well, just for insurance

AFTRBRNR

Switching from Melling 10295 to 10296 pump tomorrow. Using red high pressure spring. I should have new pressures posted by this weekend I hope.

AFTRBRNR

New conditions:
Melling high VOLUME pump with high pressure spring
Mobil 1 5w30 oil with AC Delco filter (for baseline stats)

New pressures observed:
Cold Idle 60 psi
190 degree oil, 40 psi at idle
230 degree oil, 12 psi at idle

Operating pressures 30-40 psi while driving.

No visible or audible signs of insufficient oil pressure.

Oil pump o-rings were not the cause. No visible leaks in the front and rear covers. Oil pan gaskets were tight. Galley plugs appear fine. The only thing that leaves is looser bearing tolerances as hypothesized. Next oil change I will put in heavier weight oil to check performance with the 10296 pump and report back.

Incredibly enough, none of the engines the builder has made with this exact spec have failed (that I'm aware of) and the engine was built just the same as many others.

BTW, the car drives completely normal.

pmwinc

I have a stock bottom end, and the 10296 give me 40lbs at idle, 50-
60 driving around

rabrooks

How often do you see 230 degree oil temps. Every pressure looks ok except the 230 pressure. If you see that temp often, its time for an oil cooler. Under spirited driving my Z never got above 205, 210. On the track it would get to 275 on a hot day.

Food for thought. The low pressure doesn't bother many mechanics because they prefer high flow over pressure, hence the extra clearance. So if your new pump is pumping a good volume, the pressure is probably ok. The normal temp pressures are fine anyway. Just try to find away to get the oil temp down. I run a 10w 40 Mobil 1 on the track.

AFTRBRNR

I never remember seeing oil temps above 210 degrees with my old engine. Currently I run a stock temp management system with fans set to run sooner. This new engine will go up to ~230 degree oil temp on a warm day. The oil temperatures will remain within 10 degrees of the coolant temps. I have plans for a bigger radiator with oil cooling lines when I add a supercharger.

CI GS

Wow, that's a big swing in oil pressure at idle from cold to hot. 230 is getting a little bit high, but probably nothing to worry about. I don't think I've seen engine oil temps higher than 215 or so on my car, but I don't run it at WOT for very long either. To me, an engine oil temp of ~215* is ideal, because it's just high enough to boil any moisture out of the oil.
I would've suggested that you try the 0-40W Mobil 1, but you may end up with even higher cold idle pressures then. I don't think you have to worry though. What does the oil pressure go to at high rpm/WOT with the oil hot?

AFTRBRNR

35-40 psi when hot at WOT. Cruising is a very consistent 30#.

CI GS

35-40 psi at high RPMs (like 6000+) ??
That's a bit too low for me. I would at least put a thicker oil in it, since it seems to be built for that, and see what that does.

User Omega

I have read in another thread where a Mamo build (LS7 in that case) ran Johnson axle oiled short travels. The guy saw 20-25 psi at idle and 50 psi at high rpm and it was considered acceptable. My results are the same. For reference I was at 49psi at 210 and over 60psi at higher rpm with the stock pump and non axle oiled.

I am not sure about running a thicker oil. I was always under the impression that volume trumped pressure. I also thought that if you increased viscosity that you would see higher oil temps. Unsure if that is a good idea for a guy running 230.

Any input on that thinking?

extrapilot

The OP did replace the oil pump with a high volume style so maybe the pressures will not be as high as a trade off. He also said that the builder built the engine with looser clearances, but how loose are we talking here.
Changing to a heavier oil will only make the pump work harder and rob the engine some power doing so, probably something that I would not be doing. You want the oil to flow real good as the engine warms. Some of that oil may not get filtered either, as the bypass valves will allow oil to be diverted from the filter, especially when the engine is in it's warming phase.

NJ_phil

Idle = 50 cold, 30 hot
Cruise = 40-50

Stock LS3 bottom end, 3200 miles
Oil = 5-30w Might move to 10-40w for the summer if I see < 30

Had the pump apart when doing the cam and regret not putting in a High Pressure Mellings.

CI GS

Well, my thinking on this is pretty simple: If the engine is built with looser bearing clearances, then it will need thicker oil to retain an oil film on the bearing surfaces, where it's needed. We're not talking about pressure losses from pin-oiled lifters, etc. Such things simply require more volume to keep the pressure in the oil galley at optimum, because if you're bleeding that much more oil out of the system then you need to make up for it somehow. The stock LS pumps are spec'd for stock tolerances, lifters etc. Whenever you change things like bearing clearances, then the stock pump volume and pressure setting, as well as the specified oil viscosity, goes out the window.
The OP says that the engine was set up with looser tolerances. I've always operated on the rule of thumb that an engine needs around 10psi per 1000 rpm. He now has a high volume, high pressure pump (the same one that I'm running, BTW, and I see ~75psi at 6500+) so he doesn't need to address pump volume or pressure. He needs to figure out what oil viscosity he needs to ensure that his bearings don't get wiped at high rpm. I've also seen some testing on the Mobil 1 5W-30 that shows that it suffers from thermal breakdown much quicker than the "Euro spec" 0W-40, which is a slightly thicker oil to begin with. And 230 degrees is not an extreme oil temp in any event. 260+ is where you need to be careful.
Hence my recommendation that he try the 0W-40 Mobil 1, which, according to a recent test I've seen, has a higher film shear pressure than just about anything on the market. It's a really cheap option. Of course, he could always keep the "factory spec" 5W-30 and hope for the best. I wouldn't be turning my engine to ~7000 RPM if I only saw a max pressure of 30-40 psi. 60 psi would be acceptable, but not 30-40. But maybe I'm just paranoid.

BrownVette

I'm always up for learning something new, I've seen two posts about how lifters can affect the oil pressure. Can someone explain how?


To the O.P, did you ever put a mechanical gauge on the engine to see what the readings were? There may be some argument to this, but the readings may or may not be entirely accurate, from what I understand the reason some manufactures' only have a dummy light and dont show oil pressure numbers is bc some ppl see a lower number and start to worry when in fact all is well.

Unreal

Hydralic lifters are ran by oil/pressure. If you have axle oiling/etc that is extra oil they are using, basically holes for pressure to bleed out.

Also if lifter to bore clearance is too large, they will allow oil pressure to escape past them.

BrownVette

I understand that lifters are oiled/via oil and pressure, and different lifters have different pressures and bleed out, etc. But how would lifter affect the overall oil pressure, Isnt it measured via an oil passage after the bearings that travels up throught the heads, then to the lifters, meaning pressure would be read prior to the oiling of the lifters. I undertand that pressure = measure of restriction. So i guess i can see where a certain type of lifter could cause some degree of pressure variance..