My guide to carburetor jetting for altitude. I live at 5,400 feet and every car I've bought that was set up at sea level ran rich when I got it home.

The general rule is one jet size smaller per 2,000 feet of altitude, but this is a starting point not a prescription. The correct answer comes from a vacuum gauge and a wide-band oxygen sensor. Rich at idle means the idle circuit needs leaning. Rich at cruise means the main jets need to come down. Rich at wide-open throttle means the power valve might be wrong.

Get a set of jets in several sizes above and below your starting point. Make one change at a time. Test, record, repeat. The result is a car that starts easily, idles cleanly, and pulls hard at full throttle.