lucxy

I have a built motor with Mahle forged pistons (2618 alloy), stock rods, stock crank, ARE dry sump (stage 2), PCV to atmosphere (catch can).
Piston to wall clearance is set at .0050.

I use Redline 10-40 oil, oil temps are normal (170-180 street, 200 traffic), 220-230 track. Motor makes around 600 whp, with around 7K miles on it
and has been consuming oil from day 1.

The car consumes 1 qrt every 400-500 street miles and ~1 qrt every track day. This seems like a lot to me.

There is no blue smoke at any point (startup, acceleration), no leaks.
Where is the oil going?? Is this normal or do I have a problem?

Michael_D

That is not normal. A leak down test should tell you what you need to know.

blkbrd69

A qt. per roadcourse track day can be normal depending on driver and track.

1 qt. in 400 street miles is very high?

Does it have intake valve seals like a street motor or none like a race motor? Cats will prevent lots of smoke till they die.

lucxy

The motor has valve seals. I have high flow cats and in the begining had straight pipes -- still no smoke. There is no smoke at any point at any time. I am a bit confused. I called Mahle and they said that I should have blue smoke if so much oil was burning up in the combustion chamber. Very puzzling. The car runs great and there is no detectable power, there are no misfires.

I just came back from track (roll on racing) and ran similar powered Z06s and my car performed well within the expectations.

lucxy

I get that the only way oil can "evaporate" is either by burning up or leaking out. I am assuming it most likely burning up, but where and why and how without any noticable symptoms such as blue smoke, misfires, foul plugs, power loss? Unless this is normal.

Quicker

Curious how your catch can and PCV line/s are routed.

lucxy

Dunno specifics, but it is ARE dry sump, catch can and breather, connected to the top of the ARE tank. I think it is stage 2 setup.

I am thinking my oil issue is related to ring gap clearances:

Ring gap top: 0.017
Ring gap second: 0.024

Thoughts?

rjacobs

Just doing a quick google an LS1tech thread comes up that Mahle recommends bore x .0045 for the top ring and bore x 0035 for the second ring. I cant find an oil ring gap spec except the factory spec(which may or may not mean anything with your pistons) is .0098-.0299.

So if you followed that your top would be .018 and the second would be .014.

Although in that same thread its quoted from Mahle as saying that a wider bottom gap will increase performance a bit at the expense of oil control.

What is your oil control ring gap?

lucxy

Dont have this in specs.

Michael_D

Again, not normal. Not acceptable. Not the engines I build anyway, which are mostly purpose built race engines.

One more time.....a leak down test will tell you what you need to know. If you don't understand why, ask.

lucxy

Scheduled to do a leak down test in a week. I guess the test is supposed to test intake, exhaust vlaves and piston rings. I don't get how valvle leaks can cause oil consumption, which only leaves piston rings as the only option anyway. Am I correct? And if that's the case then the only outcome is rering the pistons?

And if so much oil does get past the rings why don't I see smoke, misfires and loss of power? Shouldn't I see that with so much oil burning up?

Michael_D

The part about consumption starting at day one is troubling to me. Could be that the rings did not seat. Wouldn't be the first time I've seen that. The leak down test will tell you if there is a ring seal problem. If they test good, then you can sleep better and check stem seals. No where else for the oil to go, but the PCV system, and you said you have a catch can. No oil there, so that leaves the rings and stem seals. You must not have a leak, or you would have seen all that oil, somewhere. If it's rings, you can always try Bon Amy as a last ditch effort prior to yanking the engine. Sometimes it works, sometimes not. But if the engine is coming out, it's worth a shot.

Suns_PSD

What the hay is Bon Amy? Fine sand you drop down the spark plug hole or something to try and get the glaze off and get better ring seal?

Thanks

lucxy

I guess the question is how can so much oil burn without any smoke anywhere? Shouldn't I see smoke, assuming rings or valvle seals are leaking??

Unreal

My forged LSX uses no noticeable oil. No smoke, no change in oil level at 3-4k oil changes.

Michael_D

Not necessarily. You are not going through that much oil, in comparison to an old beater that leaves a cloud behind it. Bad or missing stem seals will generally cause a puff of smoke at start up, after the engine is off for several hours. Exh seals, hard to ever notice.

Do you have a bore scope? If you do, pull a few plugs and take a look. You can buy a cheap one for under $50 at Costco. (Just saw one)

Michael_D

It's a powder. Mildly abrasive. You dust the air intake with the engine running. It should only be tried when the only remaining option is pulling the engine. At that point, there's nothing really to loose.

lucxy

So assuming I have a problem with rings, is it even worth fixing it at this point? Given the fact that motor is running strong, no smoke, no power loss and just oil consumption. Seems like fixing will be expensive. What's the downside of just leaving it as is until some other symptoms comes up and then rebuild?

Also is it still worth checking PCV? I posted a forum question about it as well with how my PCV is routed.

Michael_D

I would figure out what is going on first, then consider options. PCV is important. You want crankcase vacuum. It helps with ring seal, and if pressure builds, you can get blow by. I do not like vented systems, and prefer to have intake vacuum pull on the system. Or even better, a vac pump.

lucxy

So do you recommend connecting valley pcv back to the intake as stock? Currently have both terminated and valve covers PCV running to the top of the ARE dry sump tank.