1949 Chrysler Windsor - Radiator pressure cap

I have a 7lb pressure cap on my radiator. It was suggested that I replace it with a 3lb cap. I cannot find any reference in my shop manual or "Parts List." What would be the correct one?

In 1949 they did not use a pressure cap. Just a plain cap, not sealed. This must have been about the last year for an unpressurized system.

Help me understand the impact of using a 7lb cap. My car does heat up driving up hill on hot days. Would I be better off using a different cap if I can find one?

A higher than designed pressure cap will increase the boiling temperature of the water and add extra pressure on the radiator core. I doubt it will make the engine run cooler and you have a chance of blowing out the radiator core.

Heat up or boil over? If it doesn't boil over a pressure cap won't help.

It sounds like you need to flush your cooling system. Suggest you drain the antifreeze, fill with water and a bottle of CLR. Drive around for a while (50 - 100 miles) and drain when hot. See how muddy it looks, if real bad repeat.

You can also blow out the rad from behind with an air hose to clean out dirt and bugs. And/or vacuum from the front if you can get at it.