I pulled a 1976 340 out of a barn that has been sitting there for over 20 years. I have got it to fire and idle for a few seconds a couple times. I have replaced the carbs, fuel lines, fuel filter, fuel pump, ignition coil, plugs, plug wires and gaskets. The motor has 90 psi compression on each cylinder. It gets fuel to the carbs and has spark. But it just won’t fire. Any ideas? Have went through a can of ether with no luck either. Have poured fuel down the plugs with no luck.