ever since i put my tf heads on i have went though 8 quarts of oil in 3000 i would only see a tad of oil burning when the car was hot. had no idea what it could have been. Here the oil was going down the threads of the screw in studs. Every plug was black somewhat. I pulled the studs out put the teflon tape on them put them in. After 150 miles the plugs look brand new. Just thought I would share this. (Now i dont know if my oil went down or anything, but I am happy the plugs looked good.

 

Congrats. That's one of the popular "mystery" oil consumption points on a small block Chevy. I've gun into it on an old set of S/R Turquers and my current Iron Eagles. Those threads are exposed to full manifold vacuum on the bottom as they screw right into the top of the intake port.