Best radiator cap pressure for a flathead V8?

[Ralph Moore]

Whats the best pressure to run at?, And will a stock Model A cap on a Model A radiator be alright for those pressures?

[FlatheadTed]

71b is what a 37 through 39 has ,are you running a over flow tank ? The seal would need to be tight on the A cap .

[Terry,OH]

The best is 0 thats what it was designed for, I ran a 3# for a couple years on an olds engine in a 40 and it expanded the 40 upper tank, it is a large soft brass tank.

[Ralph Moore]

Not running an overflow tank, I always thought the higher the pressure, the cooler the engine, to a certain point.

On a side note, it was so cold about ten days ago, a jug of antifreeze(pure) in the back seat of the truck froze solid.

[G.M.]

Terry a 3 lb cap wouldn't allow the tank to expand if it worked or the over flow tube was plugged up. A 4 lb cap or Skips 3 lb pressure valve works, at 200 degrees there is only about 1-1/2 lbs pressure unless you have a compression leak which will make high pressure in the system. Ralph, a modle A and the3 early Fords have an open system, the over flow tube is open all the time allowing water to excape. This results in low coolant and over heating. Skips 3 lb valve installed in the over flow tube stops the water from leaking and improves cooling. G.M.

[Ralph Moore]

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That's a neat idea, would probably work on other models as well.
How do I get one of those?

[Walt Dupont--Me.]

I was always adding water in my model A, I installed one of Skips 3# pressure valves in the overflow pipe. I never add water. Walt

[rotorwrench]

The pressure in the system doesn't make it run any cooler, it just increases the boiling point of the water. Once water starts to boil, it loses its ability to transfer heat. The product of boiling water is steam, which can build pressure much more quickly. I think the older flatheads were 4 LB caps until late in the 40s when they designed radiators to take the 7 LB cap. With the increase in horse power came the need for higher coolant system pressures.

Kerby

[fourtydlx]

Where do get these 3# regulators>

[Pat/Ohio]

GM has the link posted on his post. It's just under the picture of the valve. You can email Skip at [email protected] These are also listed in the V-8 Times. Pat