radiator cap

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Jun 6, 2024 | 02:56 PM

rusty48

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Tuned

Joined: Feb 2016

Posts: 358

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From: washington

radiator cap

Hey all, maybe stupid question but my radiator is leaking like a broken dam. Made the call for a new aluminum one. I know the flathead 8 radiator has a 4 or 5 pound cap. This new one is supposed to have a 16 lb. I assume I should have the original cap with the correct system pressure at 4 or 5???

Jun 6, 2024 | 04:01 PM

moejr

Fleet Mechanic

Joined: Jan 2004

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From: Mendon, Massachusetts

Run the 4 psi cap..... especially if you got a stock heater.

Jun 6, 2024 | 04:58 PM

ALBUQ F-1

Fleet Owner

Joined: Jul 2004

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From: NM

I agree with 4 psi, but the stock cap may not be the right one for the neck on your new radiator. Make sure the necks are the same depth, or buy a new 4 psi cap made for your new radiator's neck.

Jun 6, 2024 | 05:07 PM

rusty48

Thread Starter

Tuned

Joined: Feb 2016

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From: washington

good point, yes have stock heater. Ill go with a 4 lb even if I have to get a new one. Thats why i asked, many thx.

Jun 6, 2024 | 06:36 PM

bmoran4

Parts Nerd Extraordinaire

Joined: Sep 2010

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From: Western NY

The radiator cap changed from 41A-8100-A to 1T-8100-A somewhere in the 1951 model year. (Type B to Standard Cap). They both are lower pressure caps as already discussed.

You will need to be sure to match the cap style to the radiator. Most aftermarket radiators use the 1T-8100-A Standard Cap.