Try some regular cleaning solvent and then drive it. It should/ will burn off after awhile, if I'm remembering correctly. maybe someone else has a better solution. BTW, I had Jeff do a set of B1-BS heads CNC job from 440 port size to M.W. port size, they flowed 284 at .600 bfore and 350 CFM at .600 after on the same Super Flow 600 bench

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)