I purchased a used d15b7 and put it in my 91 civic wagon. I kept the pgm-fi obd0 setup. It smokes at idle and while driving. It burnt through 3 qts of oil in 300 miles.
I initially thought I purchased a motor with bad rings. Tore the head off but the walls show no scarring or signs of bad rings. So I took the head to the machine shop, got it cleaned, surfased, valves done, and new valve guides. I installed the head. And initially it smoked more than before. But simmered down to how much it used to smoke. I removed the exhaust manifold and there is some oil in the exhaust runners. Any thoughts?

 

You should have compression tested the motor already. Do that now.