318 overheating

When I took the cap off it didn’t spray anywhere. Pressure cap is pretty old so I can’t see what it is rated at. The Rad was just a generic one I found on Amazon. It’s been good for over 3000 miles so far. When it started going a little high the fuel gage was working, then when going to lunch the fuel gage stopped working. It’s done that before but never overheated. After having it home for 3 hrs the engine was still pretty warm and was at an ok temp when I rolled the key. I started it and it idled fine in park but drive it started to idle very rough. Got it to idle after adjusting the idler screw 1/8 turn. I’ll look at it again on Monday when I get home
That tells me the cap is not holding pressure. Every pound of pressure raises the boiling point 3°. A 15# cap get's you 45° and raises your boiling point from around 212° (depending on your altitude and antifreeze concentration) to around 257° and it will help prevent it from puking when you shut it off. Don't be concerned about how warm it is after it sets 3 hours. It is what it is and really has nothing to do with overheating. Now all that said, you may have other issues but don't overlook the obvious.