Oil Fouled Spark Plug

Hello everyone,
My 83 caprice has developed an interesting problem. The spark plug in the #8 cylinder keeps getting oil fouled so badly that it stops firing. The gap is completely filled with a hard black substance. It takes about 6-8k miles for this to happen. Non of the other spark plugs get this way. I get a varing puff of blue smoke when I start it cold and it doesn't smoke when I accelerate that I am aware of. Would this be because the valve seal on the #8 cylinder is completely gone allowing oil to leak down the valve stem and then onto the hot eletrode or is there something else wrong with it?

Sounds like you are on the right trail to me...

Not necessarily so much a bad valve seal, as a plugged oil drainback hole on the top of the cylinder head at the back. The symptoms are classic - pull the valve covers off and see if you can poke a screwdriver down into the holes.

While you have the valve cover off, you might as well do the valve seals if it's puffing blue at a cold startup. Chevy engine's are notorious for leaky valve seals, especially at high miles.
Note: My truck does the same thing in the 5 and 7 cylinders ever 12K or so even with brand new valve seals and perfectly clean oil passageways.

I had a '79 that would every so often foul the #8 plug. My oil return passages were clogged up and just sticking a long skinny screwdriver down into it helped. But try not to dislodge too much sludge while you're at it. It could clog your oil screen.

Bob

Just for chitz and giggles, what brand of oil are you using and what type of filter.
also a pluged p.c.v. valve could be an issue along with vacume lines being cracked or broken.
when cleaning the built up sludge /carbon out of the head ports I use a small shop-vac when scraping the head. this keeps the majority of the (crap) from falling down into the oil pan and lifter valey

Also I might add, if you're gonna clean out sludge, do it right around oil change time. That way after doing your scraping, take a quart or two of oil and "rinse" out the oil passages. This will help to get any sludge chunks out from sitting in the engine and wash them down to the pan where it can all be drained before getting picked up by the pump.

I'm using castrol GTX 10w30 and an AC Delco PF454 oil filter. I changed the PCV valve not that long ago because I thought that might be the problem as well as the breather filter in the air cleaner assembly. I just went out and looked and that filter is fairly well coated in oil again. It has about 119,000 miles on it at the moment and runs great except for the whole plug foulin up on me.

How long of a screw driver would I need to poke threw the holes?

A #2 Philips with about a 6" shank should work fine.

I'm using castrol GTX 10w30 and an AC Delco PF454 oil filter. I changed the PCV valve not that long ago because I thought that might be the problem as well as the breather filter in the air cleaner assembly. I just went out and looked and that filter is fairly well coated in oil again. It has about 119,000 miles on it at the moment and runs great except for the whole plug foulin up on me. ..

Your motor is probably pretty well sludged up under the valve covers and elsewhere. If you see a lot under the valve covers, try to take it out in big chunks and block the oil holes until you're done. I like the shop vac idea from GAS.

Bob

when you remove valve covers if the top of the head is covered with sludge remove the oil pan as well and when changing oil always make sure the engine is at running temp. if oil pump screen is sludged soak in lacquer thinner this will clean up the carbon sludge quickly. valve guides on these engines are poorly machined and as a result will give the problem you describe when head oil drainholes are restricted.............

Keep in mind that you cannot simply 'remove the oil pan' without first lifting the engine up 3" vertically, so that the pan will clear the crank throws. The advice j cAT gives is very sound and is recommended.

The screen on the oil pump pickup has a hole in the middle of it, so that the engine does not starve if the screen becomes plugged, but if oil is flowing through that hole (due to screen blockage), that runs the risk of some fairly large debris being sucked into the oil pump, where it can cause oil pump failure.

http://www.automotiveforums.com/vbulletin/showthread.php?t=696488&highlight=seafoam check this thread on seafoam.it has good results 463

check out this sight.
http://www.seafoamsales.com/
and this one as well.
wix filters are what most of us buy even though it says (whatever name).
http://minimopar.knizefamily.net/oilfilterstudy.html.
You will be impressed.
sea-foam is not a mirical cure. but a long term (one half to one year) program with an old engine. or one you would start with a new engine.
although, sea-foam will clean a ditry engine's internal parts back to new within a short time frame along with filter changes above and beyound the call. meaning, change your filter once a month and add oil to the full line letting the filter do its job. your long term results will show.

check out this sight.
http://www.seafoamsales.com/
and this one as well.
wix filters are what most of us buy even though it says (whatever name).
http://minimopar.knizefamily.net/oilfilterstudy.html.
You will be impressed.
sea-foam is not a mirical cure. but a long term (one half to one year) program with an old engine. or one you would start with a new engine.
although, sea-foam will clean a ditry engine's internal parts back to new within a short time frame along with filter changes above and beyound the call. meaning, change your filter once a month and add oil to the full line letting the filter do its job. your long term results will show.
oil filters are for the most part different in internal design. yes there may be only a couple of companies that produce them. the only way to be sure your oil filter is a good one is to cut open and look at density of filter media, the number of pleats, and quality of drain back valve this you will find is different in most cases. I use pl25288 this is almost same as wix. but not fram which i donot recommend............