Burning oil w/ good compression?! wtf?

[0range_240]

My cars been burning oil for a while, and I always thought I needed to replace the rings.. so yesterday I bought a compression tester, and disconnected my injectors, and all that stuff.. and then cranked it over.. these are the numbers I got

Cyl 1: 167Cyl 2: 167Cyl 3: 165Cyl 4: 169

No correct me if im wrong, but thats far from being low compression, and I did the test twice with similar results... So what gives? why is my car still burning oil?

It only seems to burn oil when its been idling for a few minutes and then I take off and I can see the plume of blue smoke, or when ive got the car at high rpm, and blue smoke comes out along with black crap. Any help?

[DAEDALUS]

First guess (assuming no leaks) is you have worn out valve stem seals. Perhaps also your compression rings are fine but your oil rings aren't?

[0range_240]

Whats involved in changing the seals? Ive changed head gaskets, and all kinds of stuff like that so I am confident I can do it myself, just need a little guidance

[yellow_jacket]

Not the easiest job to do with the head still on. You have to pressurize the cylinder, remove the retainers and springs, replace the seals, then reassemble. All w/o knocking the valve into the cylinder. Then you still have to worry about worn out guides. If the guide is worn out they really like to wear out the seals. It is easiest just to pull the head and fix it right usually.

[0range_240]

Any idea how much the seals are? and I have a device for pressurizing cylinders, and im meticulous with my work so Im not worried about dropping a valve...

[DAEDALUS]

Seals can't be that much...I'd guess maybe a few bucks each? I believe they're made of viton. Pressurizing the cylinder is 1 option. The other option is to raise each piston to TDC to do the seals on each. Probably a good idea even with the compressed air to ensure you don't drop a valve. A good rebuilder could tell just by wiggling the valves whether you need new guides or not. Or use a dial gauge to check them.

[yellow_jacket]

They're usually viton. That is a really good idea about the piston being at the top of it's stroke. Seals are pretty cheap. If you were in GA I would give you the seals for free. I have a set sitting it my garage from having a head done.

[C-Kwik]

The exhaust valve stem seals are cheap(under $5.00 a piece). And you can do the work with the head on. Essenitally, you remove the valve cover, and exhaust cam. You should then be able to pull out the cam buckets. I'd do one at a time to make sure not to mix them up. You'll need a special valve spring compressor. It's about $70 or so. There are a few different ones, but I found one that hooks underneath the intake cam as a fulcrum and pushes down on the spring with an arm. I had to grind down the arm a bit as it wouldn't fit inside the bucket. But once you compress the spring, you remove the retainers. Then the spring. Then you can access the seal. I suppose there might be a special tool to do this, but I don't have it and a good set uf needle-nose with some careful handling did it for me.

And you will definitely want to do something to keep the valves from falling in. Compressed air through a compression or leak-down tester attachement is a good option. Even better is to actually remove both cams so all the valves are shut, so that you don't have to rotate the crank as you move from one cylinder to the next. But then you will need to make sure you have the appropriate sping compressor (one that bolts down to something on the engine as the fulcrum). Keep in mind, compressed air can move the piston making it want to turn the crank. You should make sure to set the parking brake and stick the car in 5th gear. You might as well chock the tires as well. And don't use too much air pressure. My Chiltons manual say to use 71 psi.

Another trick you can use to keep vlaves from falling is to use a soft, but think nylon rope. Feed it into the combustion chamber through the spark plug hole. Then move the cylinder to TDC. This should push the rope up agains the valves and hold it there. Make sure you leave the end out so you can pull the rope when you are done.

Install is reverse of revomval. But you'll want to use something to push the seal down around the base. A deep socket and hammer worked well for me.

[Ambivalent]

Hey there,

My cousin the mechanic told me that if you put an aftermarket intake etc, on you car that it will burn oil for some reason....... I dont know if this true but his training is fairly current and he knows performance stuff ... so maybe its just something that we have to live with..... I havent put an intake on my 240 yet but my previous car had one and it burned oil too.... and the blue cloud and crap.......

cheers

J

[SHIEF]

I wouldn't go to your brother's shop then. I dunno what intake he is talking about, regardless that doesn't matter. No doubt you have valve stem seals leaking. When you first start it up after it sets for a few hours do you get more smoke then usual? That's an easy way to tell usually.

[C-Kwik]

I've NEVER seen burning oil because of adding an aftermarket on ANY car. I'd love to hear his explanation of why this occurs as there is really little difference between a stock and aftermarket intake in terms of function.