Oily Spark Plugs...ruh roh

[wrc3]

Hey I just pulled my plugs to put my headers on and they seem to have an oil residue on them. Could that be from the car sitting so long...like 7-8 months, or is it definitely time for a rebuild?

I only ran the engine once during those 7-8 months, but it ran great...

 

[Stallion]

If the spark plugs have oil on them, does that mean oil is leaking into the combustion chamber because you have excess wear on your engine? Does it look like you are burning oil? What's your exaust look/smell like?

 

[wrc3]

From what I understand if the plugs have oil on them they are leaking past the piston rings, which indicates a need for a rebuild. I don't smell like I am burning oil, and the exhaust smells like normal exhaust. I am just wondering if sitting around had anything to do with it, or if it really needs to be rebuilt.

B

 

[brusso]

I'm not sure about sitting too long causing this problem. I wouldn't think so but I'm sure that someone will chime in with an answer. I do know that a lot of wide open throttle and or poor pcv operation will cause this. If it is from excessive WOT then you may see oil in the air cleaner also. If it is a failing pcv then you may see oil in the pcv hose. Good luck.

 

[Mako]

From what I understand if the plugs have oil on them they are leaking past the piston rings, which indicates a need for a rebuild. I don't smell like I am burning oil, and the exhaust smells like normal exhaust. I am just wondering if sitting around had anything to do with it, or if it really needs to be rebuilt.

B

Not necessarily. Cars sitting for a long time can have valve stem seal problems. The seals get old and allow oil to pass down through the guides and into the cylinder.

Using seals made from Viton pretty much cures this problem permanently.

Before ripping the engine out, I would perform both leakdown and compression checks of all 8 cylinders and then taking appropriate action from that point.

CYa!
Mako

 

[Stallion]

How could the PCV cause oil to get in the combustion chamber? I don't understand.

 

[The73vetteman]

I think Mako has it right - valve seals. The oil will dribble down the stems and into the combustion chamber. Could well find there's valve guide wear too.

Of course, ring/bore wear is also a possibility. A compression test would help you tell.

Regarding the possibility of PCV trouble - doesn't the valve use manifold vacuum and so would pull oil into the inlet side? Or am I just blowing smoke on this?

BTW - Personally I don't think its good to leave any car just standing for 6 months. Firstly, the engine needs lubrication - isn't there a risk of corrosion if it just sits? Secondly, you miss all the fun of driving it. Just my $0.02

'73

 

[brusso]

The pcv allows for crankcase vapors to be sucked directly into the intake. These vapors are intended to be the minimal expected blow by gases that blow by the piston rings and pressurize the crankcase. The pcv is designed to regulate a constant minimal vaccum in the crankcase. Also there is a small breather element, usually located in the air cleaner housing, that filters the air that is being sucked into the crankcase. If the pcv is stuck open, and not regulating the vaccum on the crankcase, it can over suck the vapors from the cankcase into the intake. If the pcv is plugged then the pressure, built up in the crankcase, can cause crankcase vapors (oil vapors) to blow out of the crankcase into the air cleaner housing through the breather element. I've never accually seen a stuck open pcv, but I've seen many plugged up ones.

 

[brusso]

73,
I agree that Mako is more on target with the valve seals. I didn't get what you ment about the inlet side.

 

[wrc3]

BTW - Personally I don't think its good to leave any car just standing for 6 months. Firstly, the engine needs lubrication - isn't there a risk of corrosion if it just sits? Secondly, you miss all the fun of driving it. Just my $0.02

'73

Trust me if I could drive it I would. Unfortunately I have been working 9 to 5 and going to night school after that, so my availability to work on the car and get it in driving shape is not what it was before school. I rebuilt the rear end this summer, but needed to do the front before it was driveable and finished that over christmas break. Now once the headers and side pipes are on it should be fun and safe to drive.

 

[The73vetteman]

Brusso,

Regarding the PCV and oil getting drawn in to the cylinders, I meant the same as you, but you said it so much better.

wrc3 - I hope you get to enjoy your car this coming summer.