Plug fouling on 327-350

[Don M.]

Guys, I have a question on the operation of my engine. The front 2 cylinders on both sides are burning nice and clean. The rear 2 cylinders aren't anywhere near as clean. They are both somewhat black. Whats up? Carb , I guess, what am I missing? Don

[Wayne L.]

Re: Plug fouling on 327-350

Sometimes there is more fuel toward the rear of the intake manifold than at the front. Can be due to the tilt of the engine in the chassis, etc.

[David M.]

Re: Plug fouling on 327-350

Little more info: Miles on engine? Last plug & ignition tune up?
Are you sure its fuel not oil?
Worn valve seals will foul a plug but its distinctive.
Snap a pic of the offending plugs.
Keep track of the plugs and switch the black ones out for the white ones and observe what happens.
Does the engine "use" any oil?
Do you see smoke on start up?

[Don M.]

Re: Plug fouling on 327-350

Does not use oil, does smoke a very small amount, plugs were maybe 6 months old, but not a lot of running time, it doesn;t look like oil, and again it is only the back 2 cylinders on each bank, the front 2 look almost perfect?

[Frank D.]

Re: Plug fouling on 327-350

Outside chance its a fuel distribution problem - more info needed....worn valve guide symptoms are blue smoke out the back when the car is started after sitting overnight and blue smoke on deceleration (and sometimes between gear shifts)...

[Timothy B.]

Re: Plug fouling on 327-350

Don,

What heat range spark plug are you using? On the Holley 3810 carburetor there are very small constant feed holes below the secondary transfer slot that provide a very rich A/F mixture compared to the primary side.

I experienced the exact same thing on my 67 and I believe it's a fuel distribution issue, after I switched to heat range 5 the plugs stay cleaner.

[Don M.]

Re: Plug fouling on 327-350

Thanks guys!!

[Lawrence S.]

Re: Plug fouling on 327-350

I had a similar problem with my 67 L79. I changed out the points to pertronix and that solved my problem.