Pressurizing an Automotive Cooling System

Years ago, when I was talking with the owner of a Tucker he mentioned that he’d pressurized the cooling system (unpressurized systems were common when the car was built). I never thought to ask him how he did it, and now I’ve lost his contact information so I can’t ask him. I’m wondering how he might have done it. Would it have been a simple as adding a pressurized radiator cap to the car, or would there be other things involved?

If the original cap was vented, I can’t imagine what else would be needed. If the venting was located elsewhere, it would need to be blocked. Now, if the original cap design was different from available pressure caps, some inventive engineering would be needed to get a cap to fit.

Now that I’ve thought about for more than 5 seconds, it occurs to me that a radiator neck not designed for a pressure cap would require more than just a cap that could be installed. It needs to have a lower (pressure) sealing surface, an upper sealing surface, and a vent tube between them to prevent making a mess. It seems to me that the way to do this is to have a radiator shop replace the original neck with one designed for a pressure cap. Getting a compatible cap would then be easy.

Thanks. I kind of figured it would be like that.