allanlaw

No, I haven't had too much to drink. I was at Spring Mountain last weekend, and at the end of the last session on Saturday I noticed a puddle of oil under the nose on the driver side. I popped the hood and found lots of oil around the area where the intake and outlet lines enter the oil cooler. Not surprisingly, I assumed there was a leak in the intake fitting, or something else funky with the oil cooler. I cut the weekend short and returned to L.A. on Sunday (300+ miles at average 80mph on highways). There was no additional oil leakage, so I assumed it was a high pressure - high temp leak.

I left the car at the dealer this afternoon, and got a call at 8:30 this evening (they run two shifts in the service department). The diagnosis after mucho consultations with the GM service guys: if the oil pressure gets high (hot engine, high sustained rpm) the system will "vent" some oil into the air intake system, and it can exit through the air filter and end up just where I described above. The shop foreman at the dealer was incredulous, but the GM guys convinced him that this was how the system was designed to work on the Z06.

OK, I'm just reporting what I was told, and I'll see what else is on the report when I pick up the car tomorrow morning. I'm interested if anyone else who runs their Z hard (like at the track) has noticed any oil puddles on the driver side or oil moisture near the air filter inlet.

Damn, I just should have run it on Sunday like I was planning to . . .

A427MAN

Hey Allan,
I just read a post that said that the new Spring Mountain Z06 BLEW it's engine over the Vette Weekend!

Did you hear anything about it?

I'm glad I got to be the FIRST student to take her out!

Verrückt

It sounds like you may have excess blowby or have a problem with the PCV system.

How many miles on the clock? If everything is not fully broken in yet, the situation may improve on its own.

rockettc

So where does it vent the oil from? And why was this system designed to work this way? Make sure you get this explaination in writing from GM and then share it with us please. I'm not saying this is but...

Verrückt

Well, what he described is the proper operation of the PCV system. What he's not saying is that something is wrong with the engine if it has so much blowby that it's belching oil from the intake tract.

This was also a known problem with LS1/LS6/LS2 with Dana "coined" piston rings which would lose their twist over time. Some engines were re-ringed due to excess oil consumption or blowby.

I'm not saying that this is the problem in question, but it is a good idea to have it checked out at the dealer and keep an eye on the oil consumption.

m3corvette

Miaugi

fgordon

Thats pretty much of a stretch to tie the PCV system to ring blow-by isn't it? Allan did not report any excessive oil consumption. The blow-by would have to be significant to pressurize the crankcase sufficiently to vent oil thru the PCV valve in a normal system. (Maybe different in the dry sump, I don't know)

Seems to me that there would be some other cause/problem the most obvious being overfilling. I don't believe someone with a racers knowledge would overfill his engine but stranger things have happened. This also may be something peculiar to the dry sump system. Where is it vented? I'm starting to ramble here but for my 2 cents worth I would look for something other than a ring problem unless excessive oil consumption (seeing it at or out the tail pipe) is involved.

Verrückt

No, that's the entire purpose of the PCV system. Excess pressure in the crankcase is released back into the intake tract. Excess blowby is certainly a cause of excess crankcase pressure.

Under normal operation, you will get some oil and sludge build up in the intake tract. This is normal to see on the manifold and related parts.

At high RPM and load, there will always be an increase in blowby. When it becomes enough to bring enough oil into the intake that it actually drips out, that constitutes a more severe problem in my book.

You are also correct in saying it could be simply overfilled...but I really hope that is something the dealer checked considering the circumstance. If they didn't, I'd suggest you run away from that dealership and not look back.

vettemaster1

i over filled my oil and started to get lots of blue smoke out of the tailpipe when first started.....setting oil to proper level took care of the problem....

Verrückt

Be very careful. It doesn't take much oil to ruin a cat converter.

Halltech

http://www.corvettels7.com/forum/showthread.php?t=9

http://www.corvettels7.com/Z06_oil_change.PDF

Oil level was the culprit. You may have toasted your cats as well. I would dyno soon to be sure your engine is putting out max hp.

Running excess oil through the intake PCV, will cause ingestion of oil into the engine, which can cause oil-lock (similar to hydrolock) or cat roast. Both are very bad, the former being a broken motor.

The oil check procedure is critical on a dry sump motor, and must be followed explicitly. It is in your manual here:

http://www.corvettels7.com/forum/sho...?p=130#post130

Jim Hall

glass slipper

I have not heard of the "coined" piston ring problem on LS1/2/6 engines...got a link? I know about the 2001 LS6 excess oil consumption problem due to ring flutter (@high RPM/high vacuum) of the 2nd compression ring (which most people don't realize is more of an oil control ring than a compression ring)...but those rings were changed. I have a high mileage LS1 that requires no oil added during its 10k mile oil change interval, at what point in time should I expect the rings to lose their "twist"?

Verrückt

Nope, no link.

Usually, the twist in a piston ring is controlled by cutting a chamfer on the ID. This will cause the ring to twist slightly in the piston groove promoting better sealing during non combustion conditions. (see vacuum or overrun).

Under full combustion load, the ring flattens out and it isn't an issue.

The Dana supplied rings supplied in some engines (I can't give any info on how many numbers or what model years) in the LSx line had twist "coined" into them by pressing them into a twisted shape. Some of the rings lost this twist overtime, and as you know...some engines were re-ringed.

As far as I know, these problems were experienced fairly early on in the engine life and there were drastic symptoms like more than 1 qt per 1000 miles oil consumption.

If your LS1 is running fine with high mileage, I wouldn't worry about it in the least.

Halltech

The LS7 motor, does not have an oil consumption problem at all. I hope we do not revisit the LS6 ring problem, in this thread.

The oil puking into the intake is simply due to overfilling the dry sump reservior and that's it.

This is a blueprinted motor with tolerences you will not see in any street driven vehicle for under $500,000.

The block is a T6 hardened block with torque plate honed liners that have zero tolerences. In other words, all finished bores are EXACTLY 4.125".

The eutectic pistons are cast, but are hard anodized at the ring lands, and are slipper type, with moly coatings on the skirts. The tolerences are 4.124"-4.126" measured at the moly skirt area.

What that means is that the pistons must be cooler than the block to fit into the block when the engine is assembled. If a piston measures 4.126", it would be a interference fit piston. The engines are started at the factory and "run-in" on the dyno to assure proper skirt break-in.

There should never be a ring-flutter situation with this engine.

LTC Z06

Added to FAQ post# 16

Verrückt

It's a little naive to say "never".

There will always be a part delivered to the customer which is out of spec/material defect/machining defect, etc.

It happens with every engine ever built, including the Z06.

Jeepo

I was talking to the girl in reservations at Springmountain and she did say they just put a new engine in their new ZO6. They have 2 more Z's on the way.

cbgpe

I have designed and patented intake manifolds
This IS what is going on.... the oil mist in the engine is being carried over into the intake by the PVC system. Normally what falls out of entrainment in the intake air is stored in the intake manifold for drain back to the crank case at shut down. If you run long enough and hard enough and corner and brake hard you could exceed the capacity of the system to store the oil ... if it is really a problem add a air oil separator in the pvc line between the pvc and the intake

Halltech

Naive? I don't think so.

I'm am quite certain that GM's technicians have employed "Ring Gap Balancing" between the top ring and second ring to effectively eliminate any ring flutter, while still keeping the running end ring gap at around .3mm.

This technique was first utilized as a method of eliminating the oil burning problem of the original C5 oil burners.

There is also the issue of tolerences now used. Remember the zero tolerence rule. Blueprinting motors effectively prevents these types of issues most of the time.

Improper break-in, could lead to improper ring seal, however, and I may be nuts, but I have always thought that engines should be broken in on mineral based oils first, before synthetics are used. That's another discussion.