theomahamoparguy

no, you do not need the heat crossover valve for the engine to run. The heat crossover was used to help keep raw fuel in suspension during certain times of operation (like cold operation and some low speed driving). In certain applications this was actrually an advantage. One example is a slant 6 engine which suffered from poor fuel distribution. The heat riser in the manifold helped the poor distribution problems as well as helped with fuel mileage. In the 440 engine,I think there shoud be enough heat under the manifold the keep the fuel well distributed, at least after it has warmed up. One other option you could try is to remove the heat riser valve in the exhaust manifold and just leave the crossover open. This would have a similar effect to blocking it off and would take the exhaust pressure off of it while the engine is warming up. (this is because your heat riser valve when closed tries to route the majority of the exhaust from the left manifold over to the right side through the crossover passage). This happens when the motor is cold and opens after it has warmed up. If you want you could do both, block the crossover and remove the heat riser valve. This is what would be done on a race car (where heat to any part of the carb is a no no, it reduces the density of the incoming air and fuel. Distrbution is not a concern in racing mostly).
Just my two cents worth, hope some of this helps....ENJOY!!