Holley jet correction

[5150]

I was looking at the Holley jet correction for atmosphere chart,and I,m confused. Is the corrected jet number caculated at the bottom of the chart the jet I should be running, or is that what my "68" main jet is "acting" like? Thank you.

[tsanchez]

Well if at sea level you have a 70 jet then as the altitude goes up you will need smaller jets. I would say between .5 -1 jet size reduction per 1000 ft altitude change

[Mudrat]

Well if at sea level you have a 70 jet then as the altitude goes up you will need smaller jets. I would say between .5 -1 jet size reduction per 1000 ft altitude change
Seems like a lot for every 1000 feet :shock: I go between sea level and 3000 feet and I do feel a loss of power, but a whole jet size?? :-|

[AMX69PHATTY]

Understanding is one Holley Jet number change is 3% change in fuel per jet, I think, or 6% for a pair.
Funny thing is tolerance is +/- 1.5% on standard Holley jets
so in theory it's possoble to change by 1 jet size and have no change in fuel delivery.
Tolerance is tighter on Holley Close Limit Jets, about +/- 0.6%
Standard Jet part numbers are 122-xx
Close Limit Jet part numbers are 122-xx2