I didn't rebuild it, It was a rebuilt center section though, done by Turbo City in So. Ca. That's the prob with anything used, Just how USED was it? I'm still not convinced it's the turbo that's the problem though, I think I may have had a leak in my intake plumbing that was sucking air whenever I let off the throttle, and that sudden decrease in pressure actually pulled the oil past the seals, into the intake, and caused the smoking. It still ran fine, made boost like normal, just smoked on closed throttle. I could have lived with it, but smoke, leaks, and rattles bug the shit out of me. I'm just anal that way. You would definitly want to rebuild the engine before you turbocharged it, but that's the perfect opportunity to do it right, with lower compression pistons, stronger valves, etc.