78mc355350

i have a 78 monte carlo with a 350 just had it rebuilt it ran fine before just a little funky oil pressure and small tappin noise so come to find out someone else rebuilt it and put standard bearings with a 20 20 shaved crank but ne way so its rebuilt put it all back together with all new parts started it up and it doesnt run all that great if u put it into drive it will bogg down and die and spit a little gas out ive quadrouple checked timing put a new distributer in checked vaccum leaks even replaced the carb(running Edelbrock 1406 Performer 600 and msd Street Fire HEI Distributor) so i took all the vaccums off xcept the advance checked plugs they are blackened with carbon deposits i mean this motor has only ran for an hour or so not even driven wtf is going on please help oh and valves have been adjusted correctly too