I have a '69 chevy 250 and I found my number 5 plug was black while all the others were in the tan/white color range. Number 6 was darker, but within the color range of running within specs. I will be replacing the plugs, rotor, cap, and points this week to make sure everything is up to spec and hopefully solve the next problem
Next problem. My Tach will bounce around when I am holding the engine speed over 2500 with out a load and it matches the backfire(s) just about everytime. When attempting to acclerate, the truck will bog down, the tach will bounce around, and then will accelerate. I don't notice a change in engine speed during the bouncing. The bounce is between 500 and 1000 "rpm".
Any body else have any suggestions?
