- Apr 2, 2011
- Reaction score
Hey guys i just was wanting to get some guidance on this subject, ever since i had the 340 in my demon rebuilt when i restored it the plugs always look carbon fouled, ive never had a miss caused by it but they always look black. I change them every 2 years and never have a issue, im just wanting to know possible solutions or things to rule out. Now a little bit on the engine build, 69 340 block, bored .040 over, lunati voo doo cam (dont remember the specs but its not a extremely aggressive cam) edelbrock performer rpm heads, edelbrock performer rpm dual plane intake, edelbrock thunder series avs carb 650 or 700 cfm cant remember with about a 1/2” spacer/heat shield. Compression is estimated at around 10:1 maybe a little less. Running mopar chrome box ignition with a distributor from trail beast. Taylor ignition coil. Taylor thundervolt plug wires and ngk plugs. Initial timing set a 16 degrees btc and all in is around 34-36 at 2000 rpm. Engine was dynoed by the engine builder so im assuming they tuned it as well but im not sure if the jet size has been changed or not from what the carb ships with. Its been about 10 years since the engine has been built and only thing ive done to the carb is adjust the idle speed, the electric choke, and the idle mixture once. Only have ran 93 non ethanol pump gas but have recently switched to 96 vp non oxygenated fuel since there have been issues with bad gas in my town. Edelbrock recommends a RC12YC plug for these heads in which ive been running the equivalent NGK BKR5E V Power plugs. I plan to pull all 8 plugs tonight and post pics to have you guys advise me the best course of action. One question i have is carbon fouling almost always related to spark plug heat range? Or is it more common to be too rich?