mine developed an overheating problem and i found that mine had the head gaskets seeping around the center water ports on both heads . outside of that and one frozen up thermostat never had a problem . i don't run mine on the open highway due to the gearing . it just does not like to be run 50-65 for extended periods of time !!!!!!!!! that i'll cure with a different gear / diff here before long . she'd run a little warm then too , but anything i have owned with a numerically high gear ran warm at high speeds for extended periods of time not just the flathead .when she goes back together i am going to replace both pumps with the newer one carpenter has , and two temp gauges were already being used to keep an eye on her . oh and after some thinking looking etc. i believe i have come up with why my gaskets were leaking : 1. i put it together using no sealant on the head gaskets per some experts { this is my first flatty dont know shiete } and no sealant on the head bolts again per the experts . and somehow when i bought the new radiator cap a 16 pound pressure cap made it's way onto it instead of the 4 pound i thought i bought , my screw up ! caused a seam on the oe radiator to start leaking too . live and learn .

 

Washers in place of thermostats every other impeller off pumps all good fixes. The problem is the exhaust being routed thru the block. There is no real way to correct it except the fixes mentioned. Late ignition timeing will add to the problem. kotzy

 

My overheating problem is only solved when I run on the highway. Could this be a timing issue?

 

This has been a great discussion. Some great suggestions too but I don't understand why the velocity of the coolant flowing through the works could cause overheating. The release of heat in the radiator will (or should be) be greater than the gain of heat in the engine. The coolant is flowing at the same rate in either piece of the system. If it does not have time to release the heat in the radiator then it will not have time to absorb the heat in the engine either.
If it is heating up then either you are not releasing the heat in the radiator or you are absorbing more than normal amount of heat in the engine due to a crack or damaged head gasket.

 

Found most of the problem. During one of my many trips to the gargage someone reversed my fan direction. That was fixed. Truck now runs cool in the city even on a 90 degree day. Next the vacuum advance was not working properly, replaced it. Everything is fine. Runs slightly hot on the highway. I've checked everything that was mentioned to me. Only item left is to adjust the carbs. It still does backfire when you take your foot off the gas. Any suggestions on a carb adjustment?

 

Sounds like your rich o the idle. Turn one sides idle mixture screw in until the engine drops speed and back out until it comes back. Repeat on the other side. kotzy