i just put in a rebuilt 350 in a truck that i am redoing and primed the engine and got everything timed and adjusted right, but when trying to start engine it starts to crank faster like it wants to start but then dies out and then shots flame out of carb. in my past history with this it was timing but i have triple checked the timing and its dead on and i checked spark its getting good spark. could something in the valve train be bad. thanks