How the heck is it, that when you pull a spark plug there is a coating of oil on the threads only? The surrounding area is clean and the valve cover gasket does not leak. Is it just from bad valve seals or something?
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Oil on spark plug threads
- Thread starter USSkoval
- Start date
Sure thats oil and not just heat from the heads? I would think if oil was on it, it would be on the electrode side. 
I'm not much help mainly just rambling.
I'm not much help mainly just rambling.
gotblazers
1/2 ton status
you got low pressure in that cylinder. Its fuel not oil IMO
Really? It certainly looks like oil. It's nothing I haven't seen before, but this time is the first with bone dry heads and valve covers.
I guess I need to do a compression test. It was on 5 or 6 cylinders, and the truck has a miss under acceleration (but you don't feel it, only hear). It also misfires badly in the upper RPM range, but only at about 1/2 throttle. Full throttle is OK.
4xcrazy
3/4 ton status
I have had this on my dually i had alittle while back, it's definately oil, i was unsure of where it was coming from too, figured just a very light/slow leak from the crappy older valve covers not sealing tight.
this was on a fairly newly rebuilt motor as well, so i know it wasn't a "low pressured cylinder"
this was on a fairly newly rebuilt motor as well, so i know it wasn't a "low pressured cylinder"
Disciples Performance
1/2 ton status
you are going to have to check for a dead cylinder first (compression test) could be getting excessive blow by from the rings on the possible dead cylinder are the plugs fowled on the electrode? or and carbon build up??
The engine doesn't feel like it has a dead cylinder, it idles smooth and seems to make good power... it just doesn't sound right.
The exhaust smells like it's running rich and 7 of the plugs were wet with gas when I pulled them. It has done this with three carbs, this one worked perfect on the 327 (built very similar) it was on previously.
The oil was on the threads only. Not on the electrode, not on the tapered seat.
Something just aint right and I don't know what.
IIRC, it idles with good vacuum, like 17 or so. Didn't flutter either.
The exhaust smells like it's running rich and 7 of the plugs were wet with gas when I pulled them. It has done this with three carbs, this one worked perfect on the 327 (built very similar) it was on previously.
The oil was on the threads only. Not on the electrode, not on the tapered seat.
Something just aint right and I don't know what.
IIRC, it idles with good vacuum, like 17 or so. Didn't flutter either.
k20
3/4 ton status
my 496 has had oil on the threads of the plugs forever, dont really understand how, hell could just be some 'soot' and a little fuel vapor making it look like oil seeping out for all I know.
My guess is the cast iron is porus enough to let oil seep from the rocker arm areas into the threads where the plugs screw in..but if they are aluminum heads,I guess that blows that theory out of the water..
..
..
They are cast iron stockers, maybe you're on to something.
The way I see it, the seal is at the tapered seat. So if the oil is inside that, it's coming from the combustion chamber. The oil must work its way up the threads, with the stuff on the end of the plug getting burned off during combustion.
