Black plug is showing you what your combustion efficiency is looking like.... sooty plugs whether it be exhaust reversion or pig rich needs to be looked at. If it's that rich you could be washing the rings of oil. Have full compression #'s yet? About these home made headers, how long the primaries? Short tubes that dump into a 2.5 log? How about a pic?
There is other reason too what can cause black plugs, look and read link about spark plug basics what I posted before. It it written by NGK and there is good info even if you think you know everything already.
I know from fuel mileage and exhaust gas smell (yes Im that hard core tuner) that its not pig rich. I have also setted fuel screws to optimal settings. Carb is almost new and has worked before so I dont think It can be pig rich.
And if you know how engine works with big camshaft youd know that there is always exhaust reversion in low rpm/idle. Always.
Iv been bussy at work I dont have compression test done yet. The shorty headers suck for performance I know. You dont need to tell it to me after I show the pics to you. They are like normal headers but short primaries maybe 10" and collector is 2.5" and it tapers fast to 2"
