360 vs 383

Some cars run and some don’t, in my early years I had 2 1972 satellites, 4 door get to work beaters. 1 ran like a cut cat, good mileage, the other was a turd, less mileage also. Same cars, carbs rear gear and so on, was the cam off or what, I screwed with timing and such on the lazy one and never could get it to run like the other one.