Hi everyone! Thanks for the help...more problems, though. My truck overheats after she gets warmed up. It will idle in the yard fine, but if you rev it up, she steams and spits. I have had the radiator boiled out and several leaks fixed. Original 4-blade fan drawing air ok. Also overheats after driving down the road after a mile-or-so. Belts are new; not slipping. No white smoke or coolant in oil. Runs smooth. Radiator flow not sufficient?? I have heard these flathead
V-8 engines aren't happy unless they are overheating. The core is not very hot after if overheats; i can touch it all over. Any ideas...?? Oh yeah, its a '46 1/2 ton stock '49 and up flathead V-8. Thanks, Joshua

 

Make sure the block doesn't have a whole mess of crap built up in it. Anything like that blocking passages will restrict flow and cause it to overheat. Yes, flatheads are notorious for overheating, but usually it stems from a poorly operating cooling system. If the block is in fairly good condition then it may be your pumps if you've had the radiator cleaned and repaired.

Gary
==============================
46 truck-6cyl now, 302/C4 soon
46 truck-flathead 8, 4spd
47 truck-getting a 429/C6
57 Ford FL 500-4 dr-312/AT
70 Mustang fastback-351W/FMX
72 Olds Vista Cruiser-350/AT
88 Bronco II, 500,000+ mi.

 

Does it empty the cooling system or just spew for a while? And does the coolant just flow over the top or is it foaming? Two possibilities that come to mind in addition to crud in the block:

First thing to consider is filling the radiator too full to begin with - it needs to have some room for expansion. I keep mine about 2-3" below the top of the tank when cold. Just above the tubes.

Second is more serious - they can act like that when you have a cracked block. I just swapped engines in my truck because of similar symptoms - turned out to have a crack between the cylinder and the intake valve on #6 cyl. That allowed it to blow compression gasses into the cooling system. Under revs it spewed out the radiator and sucked coolant right out the exhaust until it was dry. I removed the thermostats in order to get it home - kept pressure and temp to a minimum.

Flatheads run warm, but are fairly normal and predictable when the system is sound. Don't believe that ol' wives tale that they just run hot - there has to be a reason for it. Good luck with your search!

 

Thanks guys for the input. I have flushed out the block with a running hose and nothing has come out except clean water. I don't have any coolant coming out the exhaust(as far as i can see). I fill the radiator to just the top of the tubes. It boils over once it gets hot more steam than actual coolant. I am in the process (right now) of removing the pumps. My father said he has seen impellers rot right off. Other than that i guess there is too much restriction in the radiator; recoring is my next step if pumps are ok. Thanks again. Joshua..

 

Well, I got the pumps off; no problems there. It took a while to find that pesky little bolt inside the lower hose outlet(should have looked at the service manual!). Well, I guess i'll re-core the radiator and then go from there. Thanks for the advice. Joshua.......