Soooo

I bought my truck with a aftermarket radiator cap that would leak so I went and got a used radiator cap from a 77' f250 400 engine.

I have a 351m v8 that is now leaving because of the radiator cap.

What is the correct cap for this truck and how many pounds is it ?

 

Correct cap is one that's not used and has a good rubber seal and spring . I never take the chance with a used cap unless i know it's pretty new , to easy to ruin the engine . Besides loosing all of my antifreeze on to the ground where it don't belong.I have had good luck with one that is about 13 or 14 lb. The parts suppliers in your area like NAPA or others can look it up for sure.

 

If a 14-16lb cap causes you a leak, it's not the cap's fault. Fix the leak! A new cap is like $5 why would you buy a used one?