70s CHEVY 350 CARBON FOULING PLUGS

[HDChvyTrk]

Do you still have an egr valve? And, if so, have you checked it's operation? If it is stuck open it could cause this problem. Interestingly, what made me think of this is the fouling you describe is the smae pattern as the intake manifold distribution?

[jsp282]

Yea, it does seem to follow intake distribution. No, there's no EGR valve. The only smog on this engine is a PCV valve. I still haven't done the leak test. Been busy and sooooo damn hot down here last two weeks. Don't really want to go outside during the day and when it cools off, the mosquitos about carry you away. I'll get around to it eventually. Talk to you soon, and thanks, Jim.

[AMCKB]

Where are your spark plugs gapped and what kind are you using? Sounds like you need a hotter spark!

[jsp282]

All, thanks for your replys and help. I've finally figured out my carbon fouling problem. Well, I didn't exactly figure it out myself. I was looking around the internet when I came accross an "ask the mechanic" site. Someone with exactly the same problem I had wrote in asking for some help (see earlier in this post for a description of my problem). This mechanic said chevys use exhaust gas in the intake manifold to heat the engine faster and sometimes the wall between the exhaust and intake ports develop a hole allowing exhaust gas into the cylinder. This cuts down the amount of air in the cylinder and the result is carbon fouled plugs. This made more sense than anything else I'd tried, so I bought another intake manifold. When I took the old one off, I found a break in the intake gasket at one of the exhaust ports. I don't know if this gasket was the problem or if there was actually a problem with the manifold itself. Bottom line......I put it back together with the new manifold and gasket set and IT RUNS GREAT! No more plug fouling! Again, thanks to all of you who tried to help me, and perhaps this solution will help someone else.