Radiator cap

[old guy rich]

Hi guys, did some searching but didn't find what I was looking for. Can someone tell me the correct pressure radiator cap to use on my 50 Merc? Thank you, Rich

[19Fordy]

The Mercury Manual says that: The presure cap used on the cooling systems of the CM engine is the pressure regulator type. The pressure valve in the cap opens at approx. 3 1/4 psi to 4 1/4 psi on the 1949 and early 1950 Mercury CM engines. The late 1950 and all 1951 models are set to open and 6 to 8 psi. With this in mind I would go with the 7 pound cap. Make sure you pick the cap that fits your radiator neck. Check out the various caps and vendors here:
https://www.google.com/webhp?sourcei...radiator%20cap You might be able to get one at NAPA.

[billfish]

Would Ford be different than Merc, Ford shop manual calls for 3 1/2 to 4 1/2 cap on all 6 and 8 cyl cars except cars equipped with fordomatic trans.

[G.M.]

The temperature of the engine determines the required pressure cap. If the engine runs below 210 degrees the pressure cap will NEVER open from engine temperature. The only thing that would open the 4 lb pressure cap below 210 degrees would be a compression leak into the cooling system. The pressure in the system below 210 is less than 3 lbs. Forget the term "raising the boiling point" it has no meaning in our old Fords. If they run over 210 there is a problem that needs fixing. G.M.

[old guy rich]

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Thank you 19 Fordy and G.M. I'll get one today. Rich