so it took me forever to diagnose a bad misfire
and pig rich running Lt1, engine runs super smooth and nice with the belt of.
when belt is installed I get a p0300 smoke and I bearly can keep it running, shaking
and misfiring
alternator is checked by a pro, charges a steady 14.5v
nothing else that the belt runs can make
the engine run bad so Im out of ideas

Any ideas ?? Any help is very appreciated!

 

Have the alternator tested for excessive leakage of AC current into the DC output. Excessive AC creates noise in the circuits that can cause problems with electrical control modules, particularly ignition modules.

Reference:

http://www.pvv.org/~syljua/merc/TooSeptST07.pdf