It is a 1956 BIRD 312CI FYB?
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Ethanol laced gasoline if left to sit turns to a varnish and fouls the valve guides (and other components) causing the valve stem(s) to seize, especially if left to sit for months. In addition, the FYB push-rods are solid which makes them more prone to bending and throwing (weaker than tubular push-rods), which may be a good thing as a safety feature in this instance.
You need to shoot a good
penetrating oil at the valve stem(s) and allow it to penetrate say over couple of days. Tap the stems (only) with a brass drift lightly to help free up. Don't pound. Perform this for a few days, install new push-rods (better tubular) and turn engine by hand before firing to see if all valves are free.
If you tap the valve to include the spring retainer, it may cause the valve stem locks to fall out.
Putting a car to sleep over the winter is the worst thing you can do to it (IMO). At the minimum, use a QUALITY gas stabilizer with a full tank of gasoline (double up on the amount). Ethanol laced gasoline is hydroscopic drawing moisture from the air (as also does brake fluid). The full
fuel tank will slow it down (absorption) somewhat but is still vented to outside air (pre-EVAP).
At a certain percentage, absorbed water (moisture) will separate from the gasoline and sit on the bottom of the tank. Some early tanks had a bung whereas you could install a petcock and drain the water periodically.
If possible, disconnect the gas inline tube @ the
carb (or fuel pump inlet), block it and allow the engine to burn what fuel is left in the
carb. Let it draw a mixture of fresh gas and SEA-FOAM (In a container to protect the inside of the
carb during storage). The ethanol will also foul a mechanical fuel pump and the
gas tank.
Before spring firing, replace the fuel filter. A paper fuel filter will deteriorate over time with ethanol.
