I just did a complete rebuild on 4.3 liter engine from my 1993 C1500 2 wheel drive PU. On startup it ran great, timed it perfect,took it for a 3 mile ride and when I stopped, dark black smoke was coming from the throttle body.
Oil still looks clear, oil pressure was good,no noticeable smoke from exhaust.

Engine was bored .030 over, new cam bearings, crank was ground .010 under, everything checked OK with plastigauge--I haven't got a clue.
Anyone come across black smoke from throttle body ?

thanks