I have a 312  4 cylinders are running good but the other 4 cylinders have a carbon build-up on spark plugs. Where do i began to start? 

Thanks-Zach

Which 4 have the carbon buildup?


Lawrenceville, GA

6,8,1.3

Those are pretty random. A tune up and compression check is probably a good place to start.

The only hint of a pattern I see is 8, 6, and 3 fire sequentially, but 1 is an outlier.  The 3 in sequence, maybe some sort of ignition issue.



Lawrenceville, GA