1fast97gsx

First off the car has an LSX 454 crate motor in it, but from a diagnosis aspect it should be no different. The car uses about 1/2-1 quart of oil every 500 miles or so. It doesn't get driven hard really and I don't ever see smoke out the exhaust. There are no external leaks whatsoever and I've tried switching to 20/50 oil also just for testing which made no difference. The car runs and drives fine, leakdown was under 15% on all cylinders and there are no other issues. I just have to keep putting oil in it so I'm afraid to even push it / take it to a track event. I drove it kind of hard yesterday, noticed oil dropped just a hair but spark plugs all look clean with no signs of oil either. I'm out of ideas at this point. PCV is done the way GM says to do it in the installation manual for this engine. Engine has about 25k miles on it I believe. Any help would be appreciated!

nuke61

Take off the intake and look there. 1-1/2 quarts in 500 miles *seems* like you'd see smoke out the exhaust, since there are no leaks, so that's weird that you don't.

0HP RESEARCH

More than likely it is a oil ring issue. Might not show on a compression or leak down since the top two rings are going to be the main focus on a test like that.

Assuming valve seals are all in place and in working order?

1fast97gsx

I pulled the throttle off and inspected the intake. The inside of the intake is coated with oil, it's even pooling in some spots. I read somewhere there are some orfices / restrictors for the valve cover breather line but I don't see anything in there. Are the restrictors removable? I'm thinking maybe the shop that built the car removed it to let it breathe better but it's causing it to push oil. If it were an oil ring issue wouldn't it smoke quite a bit? Also I replaced the valve seals, didn't seem to make a difference.

nuke61

Normally I'd say get a catch can, but your motor's oil consumption is very high, so you need to find out what isn't right. My guess is that the valve cover isn't shielding the outlet from oil splash from the rockers.

1fast97gsx

when I bought the car it actually did have a catch can installed and had this issue already. I removed it and rerouted all the pcv stuff the way gm says to do it to see if it makes a difference but it didn't. The catch can however barely collected any oil, very small amount compared to how much I keep putting in the car. It's being burned somehow ... I can smell burning oil after driving the car for a while and shutting it off also.

nuke61

Are your valve covers stock GM stuff? My boosted C5 used a quart every 1500 miles, and I thought that was high. I suggest taking it to a reputable shop, explain what's happening, and what you've checked.

1fast97gsx

theyre the stock lsx454 covers. I'm a tech at a dealership ( not gm ) so I'm more than capable of doing the repairs. I was considering just doing rings and sending the heads out but I just want to cover my bases before doing all that work. Do gm valve covers have built in restrictors or are they inline with the breather lines? Thanks for your help!

colanut

I would say its drafting from your venting into the intake. Are you taped full vacuum on venting.

nuke61

I don't know if the GM covers have restrictors, but they have a bit of baffling so there isn't a direct shot out the cover. As a diagnostic tool, consider doing the following:
1) unhook the valve cover to intake line and on the valve cover side, put a small air filter on it and secure it in place where if it blows oil, it won't go everywhere. You might use that catch can that you have, but put a filter on it.
2) plug the vacuum source on the intake.

Drive like that, keeping an eye on the oil level and what, if anything, is coming out of the valve cover line. If the problem seems to have gotten much better, the solution is in the PCV system. If, however, there's little or no change, it's the rings, as HP Research thought.

0HP RESEARCH

If the vent system wasn't routed right, or the baffles in the covers were gone that would show some oil use possibly, but not nearly at the rate he is claiming the engine is using. That being said, popping off the covers and adding a catch can is vastly quicker and cheaper than pulling the engine and wouldn't hurt to go over everything to make sure it is correct as it should be right, good rings or not.

nuke61

Agreed, just want to rule out the easy stuff first.

1fast97gsx

I'll take a look at it more tonight when I get home. The passenger side valve cover is hooked up before the throttle, the drivers side is Teed with the tube coming from the valley cover area and going to the intake manifold after the throttle. That line appears to have far more oil in it than the passenger side valve cover line. Is there a chance its a valve guide wear issue that may only be pushing oil at higher rpm and burning it in the manifolds, hence the reason I never really see any smoke but can smell it after shutting the car off?

pcguy2u

The no smoke fact could be just an illusion. If there are no leaks, the oil is being burned. I'd say it's just constant and not like bad valve stem seals where you occasionally see clouds of smoke.


Likely just burning a little oil all the time???


Nick

1fast97gsx

I think so too, it does however seem to use more when doing a lot of higher rpm highway type driving with getting on it once in a while. Still no obvious smoke, but definitely more oil burning.

Michael_D

The cover vents should both be routed to the tank's rearward line. The forward tank line gets routed to the CAI. The tank itself will act as a catch can to some degree. If your covers do not have adequate baffles and orifices in the vent tubes, and are routed directly to intake manifold vacuum, then you will pull oil entrained vent into the manifold. The valley vent also has baffles and an orifice. If either has been removed, you will see oil in the intake manifold. And yes, I have personally conducted a fair amount of testing and experiments with the LS7 crank case vent system. Both the valley and valve covers see a hell of a lot more mist / venting than one would think. Unless you add a solidly performing catch can to either vent point after removing the restrictions, you will see oil in the intake manifold.

And also, you said leak down was less than 15%?? 15% is not what I would consider healthy for this engine. You should be under 5% with the piston at BDC.

1fast97gsx

Thanks for the reply, I will recheck leakdown with engine hot and pistons at bdc. Pistons were in random locations when I checked it since I used a leakdown tester to do my valve seals and basically just pulled the rockers and took note of numbers the tester was showing but I didn't turn the crank at all during the whole job ... also engine was cold. I'm not familiar with factory ls7 routing of pcv but my lsx454 is not set up for a dry sump and does not have any extra tanks or catch cans or anything. I suppose I can run the valve covers and the valley pan line to an externally vented catch can and block off the intake fittings to see if the can fills up in which case it would have to be a ring issue correct?

Michael_D

In your case, I suggest you give Dave at Mighty Mouse a holler and see what he can build/supply you. His catch can set ups are the best thing going for modified vent systems.

When you do the leak down, and you see what appears to be high leak by rate, rock the piston back and forth to get the rings to square up to the cylinder. I don't bother doing it hot, because the engine will be cool before your done.

David@MMS

lets see some pictures of the set up

pcv is one of 3 places you can internally lose oil, it sounds like it is contributing to your loss at a minimum.

meanjoe

Curious how this ends up.