I'll try and keep this brief. I'm running a BBC with banks twin turbo deal on it, the thing smokes like hell out of the left bank ONLY under 1500 rpm. The engine was fresh last fall, everything was rebuilt except the turbo's, I'm been suspecting a leak on the compressor side of the turbo but that would cause it to smoke out of both sides.? I pulled the left head and found oil in #7. I had new guides installed, tossed the umbrella seals, and put positive valve seals on all 16 valves,.. still smokes. My machinist says if it were rings i woudnt have had oil on top of the piston, must be valve seals.? I've probably got 15 hrs of tuning on this motor and it smoked when i first started it last fall and still smokes now. The only thing that i've noticed is it will smoke much less with less timing (Ignition) and more with more advance. WTF is going on here? engine runs great but the oil burning is just plain embarrising. Any thoughts?