stealth1281

I just swapped intakes and my engine builder said my car has some major blow-by since he found oil in my intake and my rings are about shot and my engine will only live for another 2 years before I'll need a new one or rebuild it for 7-8 grand.

Guys at the track say I'm blowing out blue or white smoke out the exhaust. My bulder said that's a common issue in an LS7, but that is the first I ever heard of blow-by issues.

My car is a 2009 with ~34,000 miles and a h/c/i car making 570rwhp/526rwtq. Is there anything I can do besides tearing my engine apart? Thanks in advance!

Unreal

Some simple diagnostics will tell you what the issue is. Start with a compression/leak down test.

Lawdogg

I've had two LS7s in my Z06 with lots of track use. Neither had any blow-by. No blue smoke, didn't use oil. I've seen many Z06s at the track and never saw one with that problem. Have seen several blow up though, including mine.

stealth1281

Thanks for the replies. What could be causing this?

Lawdogg

Oil in the intake is usually taken care of by installation of a catch can. Could be your rings are fine.

Dan_the_C5_Man

And make sure you set the oil level carefully - running it up to (or past) the top hole can exacerbate the issue.

Michael_D

Have you made any modifications to the vent system? That's usually the culprit....

The leak down test will validate or dispute your builder's claim that the rings are shot.

You can install an Aviad reservoir insert to help, and a catch can is a good thing to install as well.

stealth1281

Thanks for the tips, but I already have a catch can on my car.

MyLS1Hauls

Some catch cans don't catch much of anything, and are basically ineffective. Check inside your TB and intake manifold, to see if they are covered in oil. If so, oil is making it past your catch can. Sometimes, the oil can also come in on the "fresh air inlet" side of the PCV, which sometimes necessitates a second "good" catch can on that side.

As mentioned already, I'd do a compression test first (since it is easier), and then a leak down if need be. Also, look at your spark plugs...do any have oily deposits? These 3 things should give you a pretty good indication of the integrity of the ring seal to the cylinder.

smitty1966

My 2008 started huffing a little blue cloud on startup at about 35,000 miles. I was nervous about the valve guide issue since I have a supercharger and there is more heat in the engine. Went ahead and checked valves, I had a couple that were too loose in the guides. Did the heads. Got the old exhaust valves back and one showed significant black scoring where the valve seal was failing, I believe that caused the smoke. No smoke now.

redbird555

Sounds like your engine guy may not be that great of an engine guy. Oil in the intake really sounds like a pcv issue even with a catch can you can have issues....

i would do a compression test cold and a leak down test. My bet is that engine is just fine. Ls7 aren't known for blow by and with your mods there's no reason you should have bad rings

MTPZ06

Not discrediting your mechanic, but unless he's an engine whisperer, how can he possibly know this without a leak down test? Blow-by isn't all that common on LS7's. I recall it being an issue with early LS6 engines (C5Z) but revisions were made by GM to the pistons and rings. What is common in oil getting into the manifold through the PCV system as others have stated. Not sure what catch can you're running, but if it isn't a Mighty Mouse, I would take a look at one of those. The avaid insert is another great idea.

Unreal

I would say the opposite, LS motors all have a good ammount of blow by, enough to cause an issue varies, but if you measured at WOT on a dyno the ammount of air coming out of the PCV system, it is amazing how much it is.

If leak down shows rings are good, next step would be to double check guides. Excessive guide wear will cause what you are talking about.

Also make sure you have a quality catchcan hooked up correctly. If you are pressurizing the crank case at WOT it will push oil out.

STANG KILLA SS

oil in the intake is very common on LS motors.

i bet your rings are fine.

1. start with compresion test

2. you need to know if the smoke is blue or white, the diagnosis is very different for each (coolant vs oil)

3. if you have a cam, valve seals are usually done at the same time as the upgraded springs. i had a set improperly installed once(seals). (not slide all the way down and seated) the springs essentially crushed them and they were ineffective.

4. have valve guide/wiggle test done. your due at 34k

all 3 tests are very easy to do. you could replace the valve seals and do the wiggle test at the same time for very little cost. quite simple. so is the compression test.

but again, just about every LS motor has oil film in the intake. i bet your fine. but the smoke is uncommon.

rio95

Could be from a few different things, but regardless of what some people say, GM tends to setup rings a little loose and high RPM fun only makes things way worse. Unless it's real bad, just keep an eye on the oil level and run it if you already have a catch can and guides and valve seals are decent.

AzDave47

OP has an 09 with 10 1/2 qt system. So do I. I find if I set the oil level at 175* at the middle hold on the dip stick it will be at the top hole at 265*. I have a catch can in the PCV system. I collects virtually nothing - unless I run road course events, then in 60 miles I collect 3-4 ounces running the engine up and down 4-7K rpm repeatedly. Doing 1/2 mile events - nothing. Running 90 miles in 5th at a steady 4800 rpm, virtually nothing, so it is the full throttle/off throttle in the high rpm range that has oil going into the intake thru the PCV system.

1L1keWaffles

My Vette had massive oil consumption when I bought it, I immediately did the heads. When I did the heads, I noted a lot of accumulated oil in the intake. 4 of the intake valves where out of spec, so oil could creep down the valve stem and splash back into the intake from the valve.

With the new heads the intake has stayed dry (for 2 months now, 3k miles), the blue smoke stopped, and I have not noticed any oil consumption over this timeframe. Before it would consume approx. halve a quart per 1k miles according to the previous owner.

stealth1281

I had both heads replaced under warranty. Then I sent them to WCCH only 2 years ago to be "fixed."

MTPZ06

Have you done your leak down or diagnosed your issue yet?

stealth1281

I need to find the time and a shop that will do it.