Badly oil coated rear passenger spark plug

[tigernut]

My car started misfiring. Pulled all the plugs and found the rear passenger cylinder to be the culprit (spark plug filled with oil sludge).

I would assume it is most likely the valve seal for that cylinder.

Guess it could be the piston/rings? (Although cleaned up the plug and it runs strong).

What do you guys think?

Was leaning toward pulling the motor (327-350), bagging it and dropping this in later this winter:
http://www.sdpc2000.com/cart.asp?action=prod_detail&catid=3508&pid=156334

Doug

 

[WayneC]

My thoughts:

A bad valve seal is more likely than rings, but it could just be a bad plug or even a blocked oil drainage hole in the head. There are ways to find out. Check this link for a description of a leak-down test. You can do one yourself, or have a shop do a diagnosis for you.

If you want the 383, do it, but it's a LOT more expensive than a complete engine rebuild, which you may not even need. You'll probably want to repair your current engine at some point if it's the correct one for your Vette, and you have to do an engine pull & install anyway, so you may not even escape the cost of repairing your 327/350 engine.

 

[wallyknoch]

More likely than not, it`s merely a valve stem seal. Not a difficult thing to repair.

 

[studiog]

If it runs good and strong with a new plug it isn't the rings. I would tend to agree with Wally. Valve seal. Good luck