Crowhater

This is new one on me! This is a new ls3 427 that we just fired up for the first time Friday.

The bottom end of my new engine is a dry sleeve M2 from ERL and I have all the specs for it in my build sheet. The tolerances are pretty much factory spec, and the oil pump is a new high pressure Melling. For break in I am using 6qt of brad Penn 30wt break in oil. When the engine is cold my oil pressure at idle "875rpm" is 50psi but when the engine warms up and the oil temp gets around 180* + my oil pressure drops to 12-14psi at idle. The second you touch the gas pedal the oil pressure jumps to 40+ psi. If I am driving say 60mph with the rpm at 1600 my oil pressure will be like 22psi, but if I give it any gas the pressure comes right up. I know for a fact that the O-ring on the oil pump pick up tube did not get pinched. The shop wants me to try a 20-50 oil and see if there are any changes before I tear the engine down. The engine runs great, no strange noises, the computer reads the same as the gauge also. I know you only need 10psi for every 1000rpm but I do not like what I am seeing. My thoughts are that the new high pressure pump is some how set up wrong. I tell you if it was not for bad luck I would have no luck at all. Changing the oil pump is a major PIA so I would like to hear some thought on this before I tear this new engine apart again.

Could the strait 30wt Brad Penn brake in oil be the cause of this? If you give it any gas at all my oil pressure shoots right up. The oil plunger was installed in the back of the block correct and I have zero noises, everything is 5x5 except for the low oil pressure at idle when the oil is hot. The lowest it has dropped to was 11psi at 875rpm with an oil temp of 245*, but like I said when you give it some gas and leave idle it jumps right up like a rocket to keep pace with the RPMs.

realcanuk

Don't think the oil would cause this. If possible I would hook up a mechanical gauge to rule out the sending unit being bad before tearing out the engine.
I have the same pump in my engine and that thing makes tons of pressure. Lowest I see at hot idle is near 40 psi.

Crowhater

Were is an oil port on the block that I can hook up a manual gauge?

sammyv

I def would wait till I changed out the beak-in oil before I did anything else! Then recheck your press. Let us know.

Crowhater

I can change out the break in oil today. I bought 3 oil changes worth of the break in oil and filters.

What concerns me is the huge swing in oil pressure from cold to hot. you are talking about a 40psi difference.

I am thinking about checking the intake valley cover tonight to make sure the O-rings under it did not get damaged or fall out. It is the easiest thing to inspect first.

realcanuk

I don't think the break in oil is an issue. I am not sure for a gauge hook up. There is a port at front on the drivers side that I used to prime the engine before start up. I guess a gauge could be hooked up there.

Bill Dearborn

Straight oil may not cause that much of a drop in pressure but it definitely will change more than a mulitiviscosity oil will do as it heats up. It seems like the pump would compensate for that to some degree unless there is an issue with the pump or you have a leak in the oil system that starts flowing more as the oil warms (doesn't seem likely). The cheapest and easiest thing to do is to change the oil. I would do that first. If it doesn't change then start with the next easiest thing, etc, etc. Definitely, look at the pump before pulling and disassembling the engine.

Bill

realcanuk

The reason I doubt its the oil is because I just did my build, with a Melling high volume pump and the pressures with the break in oil (Joe Gibbs) were the same as the normal that I switched to after.
Still worth trying I suppose and it would be great if that's the issue.

timd38

I know another fellow with the same issue. He attached a mechanical gauge and the problem was the gauge.

gotjuice?

Check with ERL. Mine seem to be lower then what I would of expected. They say all is good if it moves up quickly when you increase the rpm. I was going to change to 15w-50 and see what that does. Have not had any time to do it lately.

cclive

This is the first one of these 'low oil pressure' threads where I think that it is actually too low. Many people have never had an oil pressure gauge before or have never cared about it until they bought a Corvette. Yours actually sounds like there is some sort of problem. I would not expect the kind of oil to make the kind of difference that you are seeing. Maybe contact the people at Melling and ask one of their engineers for an opinion..they certainly know oil pumps better than almost anyone else. Be sure to let us know what happens...

Crowhater

Well I changed to Quaker 20/50 like people suggested and it started up cold with 50+psi of oil pressure like the Brad Penn. by the 160* mark where the Brad Penn had dropped to 11-12psi the new oil was 22psi. I screwed around until the oil temps got to 220+* and the oil pressure with the new oil was 19-20psi at 875 idle. The biggest difference was driving around. The old oil would be in the 20 range while cruising with the RPMs at 1600. The new oil holds over 40psi doing the same thing. This is on par with what my factory engine did.

I can't believe a start 30 weight is that big of a difference. I wonder if they designed the oil to do that some how because it is a break in oil.


Do my new oil pressure numbers seem more on par with what they should be?

Bill Dearborn

Glad to see changing the oil had such a dramatic effect. It may not have been the oil but something that got drained when you drained the oil. I would check to to see if it meets GM's specs with oil temp at 212 degrees. At that oil temp the pressure should be above 18 psi at 2K rpm and above 24 psi at 4K rpm. I really can't think of what my pressure at those rpms since I mostly monitor oil temp when on the track. My oil temp hits 260 on track and once that hot I think the pressure sits somewhere in the low to mid 20s at idle and jumps to over 40 if I just hit the gas enough to take the rpms up to 1500. But, as I said I don't pay that much attention to it as long as it is good enough.

Bill

realcanuk

I would speak to your engine builder about this. Although the pressures you are getting now seem ok, They are still lower than what I get usling Joe Gibbs LS30 oil. I cant see any reason your should need to use a heavier wieght oil to get proper pressures.
One thing just came to mind. You said in your first post, "melling high pressure" oil pump, which is what I use. Are you sure it is not the "high volume" pump ? Many use that pump and that could explain the difference.

Meir David

Hai friend

I had read out your post twice but i cant get your Question clearly.so i am not having any ideas to post

Crowhater

The pump is suppose to be a high pressure.

This is not the oil I will run in the car, I only installed it for break-in. ERL told me to run a non synthetic oil for the break-in period and do not switch to synthetic until after 2k miles. I will switch to the Joe Gibbs.

pit-man

Did you use a brand new pick-up tube o-ring ?

I reused mine during a cam change because it still looked new and was low miles. My Oil pressure did the same as yours. I bought another one, and pressure went back up at idle and all good for 4 years now.

Crowhater

Everything is 100% new even the lifter buckets.

realcanuk

I guess every builder has their own system. I used break in oil on first start, changed it after the tuning and dyno. Used break in oil again for about 300 miles, and then changed it again to Joe Gibbs LS30. Pressure was the same each time. Check with your builder, or invoice if you bought the pump yourself to know if its high pressure or high volume. If it is high pressure, then something doesnt seem right.

zo6style

How is the engine working? Did you ever find out what was causing the pressure variations?