How do modern cars regulate temperature so well?

Jeff, Tell us about your Motor. Stock build. Stock cam. Bored over.
Reason why I ask. I've owned a lot Of Mopar's. The Only one I ever had a problem with running
Hot was a '66 Block 440 it was bored .60 over I drove on the street every day. The machine shop
said they needed to go that far over. I wasn't happy about it. That car ran Hot from the day I put it in my
car. Did it have a blocked water jacket. Probably not, But maybe. Or Maybe Cuz less material on the cylinder wall's.:(
I just know That was the only time I had a problem. And I lived in Florida most of my Life. And half of My Mopar's have had A/C.