My S/B 350 began fouling plug No. 5 a few K miles ago. Plug electrode and insulator has heavy, hard carbon deposits after 2K miles. Threads of plug are oily (liquid). A little smoke residue on the bumper where the left side exhaust exits. I presume I have either a leaky intake valve seal or a ring problem. How can I tell which? If it's a ring, will it lead to other problems if I ignore it? Advice please. THanks. -DK

Have someone follow you. If it smokes when you have power on, its probably rings. When gearing down, probably valve seal. A bad seal will also show smoke when you first start it up, then clear as you drive. Might check where your PCV valve hose enters the manifold. If the valve is used up, can allow oil to pass into intake path.

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Dave Bradley
www.corvetteforum.net/classics/d1_bradley (http://www.temp.corvetteforum.net/classics/d1_bradley)
'69 SS396 ragtop
'33 3W Coupe
'65 Vette BB Roadster

[This message has been edited by d1_bradley (edited 11-07-2002).]

Thanks. I'll check the power on/power off scenario. It's not the PCV valve because all the other plugs are clean and dry. Just No. 5. BTW, block has about 100K on it as a daily driver, not abused. Heads were rebuilt about 20K ago (WP S/Rs).