What are the main causes for my spark plugs getting black powder build-up on them every few weeks and how do I fix it? Burning oil? How?

Orionsax7@cs.com

You did not mention what year vehicle / engine or what carburetor.

Is this "black powder" a dry sooty substance? If so it is a common problem on the Slant 6 in the mid 70's, particularly # 1 and 6 cylinders. Comes from short trip driving and choke out of adjustment or remaining on too long.

Somewhere I have the factory service bulletins from the mid 70's and have found information about this problem. They say to be sure the choke is working and adjusted. Also for some 1975 slant 6's there was some carb service package for this problem. I have a 1976 model year Holley 1-bbl carb that has a different venturi design that was to help cure this sooty spark plug problem.

Another idea.......my 1987 Dodge D150 truck with slant 6 has a choke thermostat with a few extra wraps to the bi-metal coil. It opens much faster than the chokes on my older slant 6's. And seems to do so at lower temperatures. This may help you out too. I'm sure they changed to this faster acting choke thermostat for emissions and fuel economy reasons (and sooty spark plug prevention??).


cfield@ll.net

Sorry about the lack of info. I have a 1965 Plymouth Valiant V100 with a 170 slant six. The dry powder forms on all spark plugs. The choke works fine. The heat riser valve is stuck towards the block(open?) Anyone have similar problems? Solutions?

Orionsax7@cs.com

If the carb. is "rich" or if the spark is weak (or late)the soot will form.
Tune it up, check the coil and dist cap, advance the timing, be sure the valve lash and choke systems are working correctly. Dist. Vacuum & mechanical advance needs to be working and "aggressive" (faster rate) for a 170.

Last will be leaning-out the carb., realize that the factory used smaller 1 bbls (1 9/16" throttle plate size) for the 170 and most have been swapped-out for the larger 225 carb, this is OK but may need a "tweek" to run correctly on your 170. The last thing is to just drive it hard, no "putt-putt" stuff.
DD