Have a question for you guys. Just picked up an 81 d150 with a 69 440 in it. Got it running and the engine smokes blue or greyish at an idle and real bad under acceleration. Set the timing at 10 degrees and starts well. Ran a compression test on it and have 170 psi average but 3 holes are down in the 155 to 145 range. Would you expect rings/wear to be the issue? Or would hou expect valve guides and seals? How would you go about diagnosing my issue?

Yes I'd do a leakdown if you can borrow a tester. Might just need a new valley pan & the superformance thin (.015") side gaskets (my preference). Eng might be extremely worn (rings and or guides) but changing the valley pan is pretty easy on a BB & sure beats the alternative. Otherwise I'd consider reringing it with some file fit moly rings/dingle berry honing with a 320 grit flexhone & read "breakin secrets" at www.mototuneusa.com or better yet build up a stroker & put some torque into that truck

"smokes blue or greyish at an idle"
Classic signal that valve guides and/or seals are shot.

"(smokes) real bad under acceleration"
Classic signal that rings are shot. Acceleration builds cylinder pressure. Bad rings allow some of the pressure to slip past them, unloading the oil ring.

Better start planning for a rebuild. It sounds to me that the engine is worn out, not surprising considering it's 46 years old.

R.