I bought a used engine few weeks ago, we finally put everything back in today. Problem that i'm having is when I try to start the car at first it sounds like its going to start but then it starts making this chrrr chrr chrr noise then gas smell starts coming and it doesn't start. we checked everthing like wiring, connections etc but can't seem to figure the problem out. could it be the timing is messed up ? , we did everything by the repair manual. Any kind of wild guess is welcome. I live in vegas, anybody knows a good mechanic or maybe wanna help me out. thanks

Did you put oil in the engine first?

yep.

Did you check to make sure the plugs are firing?