Is there a general rule of thumb as to how many jet sizes should be changed for say a 1,000' density altitude change? I have a 604" with a 14-71 with 3 900 CFM carbs. (See attached pic). On the dyno we got a nice 12.5 A/F ratio with 83's in the primaries and 88's in the secondaries. (The carbs have power valves too.) The density altitude during the dyno pull was 3400' according to my weather computer. How much do you think I should increase the jet size at 2400' and again at 1400' in order to be able to keep the 12.5 A/F ratio? Also, can I get away with just changing the secondaries or should I also up the size in the primaries. (It's a pain in the butt to pull all 6 bowls to change all the jets). Thanks in advance for any thoughts.