Long story short....bought a 49' with all original parts. Swapped out the old flathead for a chevy 350 and 700r4 trans. I kept the old radiator. The problem, well I should say one of the problems is my radiator constantly overflows. I am assuming this is because I have a 7lb radiator cap on it. The radiator fill neck is 1'' long as opposed to the standard 3/4'' neck on newer radiators. I have been told it is impossible to find a 16 lb cap that will fit my old radiator. So.....has anyone else encountered this problem? I really dont feel like putting in a new radiator in because I like the look of the old one. The only thing I can think is maybe cut a 1/4'' out of the neck and weld it back together so I can use a new 16 lb cap. Any suggestions?
Well as much as I enjoyed the 105 hp of the flathead I thought I might go for something with a little more power. However, I do miss the old trans.
fyi... "for every pound of pressure you add to your radiator cap you increase your boiling point 2 degrees"
I would think a 16lb cap will help increase the capacity of your OE radiator, as the increased pressure will likely expand the tanks like balloons. Old radiators weren't made for that kind of pressure.
You need a new radiator, the motor you are running needs a pressurised system. The radiator is built for a non pressurised system. Have one made or find a new one that fits. If you just run a higher pressure cap you will probably pop a seam on the radiator.
Get a radiator cap that is made for your radiator. 4-13 lbs take your pic. Macs lists pressure caps for your radiator so I believe it was originally pressurized. The cap has to fit the neck. Macs has them here. I have cooled several stock SBCs with flathead radiators. A 34 and a 36 both of them were not pressurized. If you still have boiling over problems try to figure out what is wrong and don't try to just fix the symptom.
If you don't have a coolant recovery bottle your fluid level should be down approx 3 inches from to of radiator, for expansion.
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