If this is a vortex 454 engine and hard starting after it sets for an hour or over night then it could be the fuel regulator. The fuel regulator is under the intake manifold cover and if faulty it will slowly leak fuel into the intake. It takes sometime to leak enough fuel to flood the engine on start up, this is way it starts fine after its been running. Usually there will be no other symptoms only hard starting after sitting for a period of time (depending on how large the leak is). I hope this helps you out.