The correct answer requires this data
- Quadrajet code number
- Engine specifics
- altitude
If the carburetor is original and unmolested, then the Main Air Bleeds (MAB) play a huge role in the calibrations. Think about why a 74 chevy 350 smog motor would have 77 jets, while a 70 Stage 1 Buick 455 would have 70 jets. Jet size does NOT equal more power. The primary rod is a restriction inside the jet, and the size of the rod/jet combo is always considered.
We look at factory settings and make adjustments based on engine modifications and driving desires. But the original settings is always a good place to start.
Altitude plays a part, but typically, we wouldn't adjust size unless you are over 5000'. One size down on jetting at that point.
Point is, check with us for proper jetting options for your carb if you aren't sure where to start. We have data for most Quadrajets and know where the starting point should be.