BoostedD15B7

I pulled the plugs out of my del sol today to do a compression check and all them were saturated with oil. It was just dripping off the threads. I have 200 to 215 compression on all the cylinders. What would cause this? Way too much fuel maybe? Thinning the oil out real bad?

shawnhayes

Boosted/high vacuuming the PCV system.

This is what oil catch cans are for.

Under boost, the PCV system can be "sucked" by the intake, sucking nearly pure oil into the intake stream. This can cause wet plugs. Check the intake manifold. Find oil in there, you know this is the problem.

Bad valve seals can also cause this problem. Oil can leak down the valvestems into the piston chamber. Also, too much fuel on a wet plug can look like oil. Fuel dilution of oil might cause this too.

Do some tests:
compression
leakdown
exhaust emissions

If these are in spec, I'd really not worry about it. Whatever problem you have will have to get worse to be a significant difficulty.

Shawn

GreenBean

When you said the oil was coming off the threads, was the oil on the plug hole,
like maybe the seals under your valve cover was letting some in, or inside the
combustion chamber?
Was there any oil on the sparg plug wire ends?
Just curious...

shawnhayes

Good question. Maybe just valve cover leakage, eh? never thought of that.

Shawn

BoostedD15B7

i had a little bit of oil on the end of my wires and on the top of the plug, but i dont know why the seals would leak. They were pretty new and last time i changed the plugs it was fine. If that was the problem, could the oil leak down through the spark plug washer gasket and onto the threads?

I took the valvecover off today and put brand new spark plug tube seals on and put a little sealer on them. I'll see what happens in a day or two.

DragII

if oil was on top, it's definatly the seals.

BoostedD15B7

Shawn...........
How does the oil catch can work? Do you have to empty it? Does it fill up or what?

shawnhayes

You do have to empty it because it can fill up.

The oil catch can goes inbetween the PCV system and the intake manifold (vacuum). Some people propose a catch can between the valve cover breather and intake hose, but this seems to be overkill. Some links for you:

A picture:


A detail:


A diagram:


A company called Cusco fabricates these now, both universal and specific for different systems.

That help?

Shawn

Briman2021

after reading the part that said it helps stop detenation, and that the engine could handle about 3 psi more, does that mean that it could also handle more compression on an N/A motor, and if so, about how many points??

shawnhayes

No, it won't help detonation on an N/A motor. I don't believe N/A motors produce higher vacuums at WOT. Supercharged/Turbocharged motors can produce very high vacuums pre-compressor. Some setups place the PCV inlet before the compressor, subjecting it to a turbine or screw generated vacuum.

N/A motors go to almost zero vacuum at WOT (if the intake is manufactured properly), and then suck LESS oil than when they are at idle. So, the answer is no, as best as I know.

Shawn

Addendum: I thought this was an interesting question. I posed it to my other friends. They think it might help detonation even on N/A motors, although the stock PCV valve and oil separator should do the trick. They said that the residual oil vapors in the intake could theoretically reduce the effective octane of the fuel, even if the PCV valve is successfully closed, but they aren't sure. Can't give you a definitive answer, sorry.



[Modified by shawnhayes, 2:17 AM 6/10/2002]

BoostedD15B7

Thanks for the info shawn. Helped out alot. I found the cusco ones custom fit for a del sol at options auto. Thanks again.