i have a 77 454 i have rebuilt several engines but this one is giving me fits no matter what i do it is spitting the gas out the overflow of the carb every time i crank it over i have checked the cam timing . valve adjustment . and ignition timing

 

I know this is what you have checked, but recheck the cam to crank alignment

 

I just finished pulling it down the there is only one key way and one timing mark but its about thirty degrees off from the harmonic balancer timing marks on the crankshaft gear

 

Is this the same the first time you tried to start it?