My son's Duster with a 408 and a Champion radiator.

The car cools fine. The thing is this, with the Champion cap on, the hoses swell up like a tick that's about to explode. I put a JY 16 pound cap on and it's a little better but still the hoses are very, very rigid and expanded.

I saw an Allpar article on Radiator caps. I guess they cover everything.

Here is what they say about the valve that is at the bottom of the cap....

1976 FSM (Factory Service Manual) has to say on page 7-8:

The vent valve at the bottom of the cap should hang freely. If the rubber gasket has swollen and prevents the valve from hanging loosely, replace the cap. Hold cap in hand upside down. If any light can be seen between vent valve and rubber gasket replace cap. Do not use a replacement cap without this vent valve that hangs freely.

Ok, so I took the cap out of my Cuda and the valve hangs freely and I put it on his Duster and guess what. The temp stays where it should and the hoses are not ready to burst.

The question is who carries the cap that he needs?

Thanks