Year ago the engine had no leaks, run properly but had NP366 pistons and very low compression. During the car rebuld the shop disassembled the engine and swapped the pistons for KB400, they also slightly milled the heads and they measure 85 cc, the block deck was also milled a little due to corossion by one of water channels.
They reassembled the motor with my old lunati 60302 cam, valves, new valve seals and all new gaskets, rings plus steel 0.020 head gaskets. Then they tune it with O2 sensor. When I took the car from the shop it was idling ok, better than year ago. It was uring the trip home (110 miles) when my bro spotted that cloud of black smoke after heavier acceleration.
During the car resto I spoked to the engine man in the shop several times: they checked the bearings, laped the valves but didnt tell a word that valve guides are shot. I asked about degreeing the cam but in this country NONE does it. They dont even have a degree wheel (bear in mid this is the best workshop here and they maintain their own mopars too). They just lined the dots, like I did when installing the cam the first time. It was running fine.
Under the hood there is no ticking noise of leaking manifold gasket, the valley pan and carb base look ok but I'm gonna spray the joints with carb cleaner and look for air leaks.
I guess it's the valve guides and that would also cause smoking during acceleraton - when pistons suck oil thru/by the guides (?).