Motown

Ive been having to change this plug in cylinder 5 every 300-400 miles because it will plug up with oil and stop sparking. I have a hard start condition sometimes, I see a little smoke at idle, and a little blue smoke at startup.

I made a mark on the top of the porcelain on the spark plug as it sat in the head, and when I pull the plug, the oil sludge is on the same side as the mark, meaning that the oil is coming from the head, not the rings. The other half of the plug (that faces the cylinder) is clean.

Cyl 5 is the worst (plug shown) cyl 1 and 3 have symptoms too, but not anywhere near as severe as 5.

This plug has 300 miles on it. Does the symptoms above indicate a bad valve seal?

305 TPI, 103k miles.

8t2 z-chev

could be sucking oil through the PVC -my crossfire was
doing that some though not as bad as what you show
-i don't know if there was someting wrong with the
baffle in my 'vette rocker covers(looked ok)but i put an
oil seperator in the PVC line to cure the problem.
I suppose bad valve stem seals could be causing the
problem too,but what you show would be a pretty bad
case-should be smoking a lot...

Tuned Performance

iTrader: (92)

time to do a leak down test.

AlkyIROC

My 454SS fouled up plugs on the passenger side about every 3000 miles. I changed the valve seals and the fouled plugs went away. The only way you'll know for sure is to change the seals.

There's also a possibility of bad rings, worn cylinders, worn valve guides etc. Changing the seals is a quicker and easier fix. A compression and leakdown test can pinpoint other issues.

Tuned Performance

iTrader: (92)

they use to sell anti fouler's that place the spark plug in a little chamber to prolong fouling just a band aide.

vicg1

I had the same on cyl 3. Did valve seals, even though they looked ok and valves felt like they were not "sloppy". Still had the same issue. Used a plug fouler and the car ran fine for about 1000 miles.

Pulled the plug out, still good! Compression on that cylinder now 35 pounds... putting a little camera into the cylinder showed a strange growth formation on my exhaust valve... not the typical oil sludge build up but really strange reddish "*****" growing all over the valve! Cross-hatching still clearly visible on cylinder walls.

Will be pulling engine soon to do a top to bottom rebuild...

Motown

So youre saying that valve seals are not my problem?

vicg1

Nope... don't know your car... but it wasn't my problem! You will probably get a better idea once you pop off your valve covers and see the state of your existing seals...

Damon

It's almost certainly valve seals PLUS something else. Like a badly worn guide (hold it slightly off it's seat and wiggle the stem around while you have the springs off to change the seals), or shot intake manifold gasket, etc.

Just bad seals shouldn't cause THAT much oil on the plugs in only a few hundred miles.

eighty8

To quote the chart in Haynes manuals "Oil is leaking past worn valve guides or piston rings into the combustion chamber ". Couldn't have said it better myself

Twin_Turbo

iTrader: (25)

thats a lot of oil, probably bad seals and loose guides