piston question
 

I have a 350 that has a spark plug that keeps gumming up. Am I right in thinking its the piston ring? If so, do I re-ring just the one or all eight? If its not the piston ring what is it?

Re: piston question
 

It's likely a valve seal.
Clean the plug real good or use a new one, run it awhile (go for a cruise), pull the plug and look for oil on the plug threads.
The only place that oil will come from is a valve seal that's caput.

Re: piston question
 

I didnt even think about the valve's. Ill try you test out. Thanks...

Re: piston question
 

First thing you should do is a compression test. This will tell you the condition of your rings and/or valves. If you test it and have low compression numbers, add a teaspoon of oil to the cylinder with low compression and test again. If the compression rises after that, you have worn rings.

One thing you can do (as a band aid) if you do not want to repair anything right now is run a hotter plug. That will help burn the oil off of the insulator and keep it from gumming up.