High pressure radiator cap question

So my truck has a commodore engine, commodore rad hoses, and steel heater pipes up to the firewall.
The radiator is probably from another mitsubishi, or a modified original, and I have the standard 1st gen heater core.

The radiator cap that was on the truck when I got it was a 13psi cap. The commodore would have had a 20psi cap.

I don't lose fluid, but the overflow tank does gain some when it heats up. Engine doesn't seem to over heat (gauges are not reliable, nor is the Internet for where they should sit)

I think I will swap out the cap for the 20psi one, as that's what the engine was designed for. But my concern is that the heater core or radiator may not agree with the higher pressure

Has anyone ran a high pressure cap on their truck and had problems with the radiator or heater? Obviously I'm not too worried if something fails because it's old and corroded, more if a good condition system just isn't up to it



-gauge seems to sit at half cruising on the highway, gets up to 3/4 with city driving, but never higher even on the hottest day in the worst city traffic. Internet says it shouldn't even get past 1/4 for the vp engine. VR engine should sit around where mine does

I would be cautious about running a high PSI cap. Especially with the 30 year old heater core and valve that weren't designed for those kinds of pressures. I would also be worried that the Mitsu radiator won't like being under that kind of pressure either. The overflow bottle is doing it's thing but if it's not returning into the system I'd check the overflow seal in the cap. I would run a real temp gauge instead of the guessomometer in the instrument panel. A few extra gauges are a good insurance policy. Eediot lights and iffy instruments will get you so far...

No the engine sucks it back in when cool, so there's no issue atm. Ive got a infrared thermometer on its way to check the rad temps to see what the gauge notches equate to.

That said, the radiator is good condition, and copper with metal tanks, if one did fail it would probably be due to old thinned out solder I'd say. And I can't imagine holden did anything real special with their heater cores. I wouldn't try it with old plastic tanks tho.