93 engine swap

Hey guys, we just swaped out a engine in a 93 metro, having problems with it back firing threw the carb. Everyone we have spoken to says this is a timming issue.

Both valves are closed, piston at top dead center, what are we missing..?? Where should the timming marks be..?

Any help would be great.

to see if belt is on right take cover off, dowel in cam should be straight down and mark on gear should line up with notch in valve cover/belt backing plate on top . keyway on crank should be pointing up and mark on gear should line up with mark on oil pump housing behind it