Just for future reference, the bungs are 14mm. I have a box of them here, I weld them into every car I tune for myself and customers. In a pinch if you're looking for a plug, use a spark plug, it's the same thread.
DA is density altitude. Weather conditions play a huge roll at the track, when figured into the actual altitude the track is at. The car can swing a full second when you have extreme DA's from one end to the other. Tuning for it keeps you busy. The only way to document progress is to keep tabs on DA and use the correction factor to see if the changes you made were the right direction.
I fight altitude here all the time living at 5,000 ft and then driving to the valley frequently at about 1,000 ft, or up higher to 7,000 +. Then toss in the weather conditions that can swing the DA even worse. On average summer days I can drive off the mountain from 5,000 ft to the valley and see a .4-.5 change on the wideband (going leaner). I tend to tune each car to find a happy medium that suits the drastic elevation changes around here. I usually shoot for just a tad on the rich side up here at 5,000 ft, about .3-.4 richer on the AFR, so that when the car goes down near sea level it may be nearly spot on or only .1-.2 lean. So you have to "fudge" it due to the terrain we are in.
Quadrajets are a little more forgiving because they have a more precise metering circuit. Holleys usually get into modifying idle feed restrictors and high speed air bleeds to really fine tune it. The HP holleys are nice with their screw in air bleeds, I can simply change high speed air bleeds in a minute on the side of the road and affect the AFR .3-.4 tenths if I want the car closer in the terrain I'm driving in. Sorry for babbling but it goes on and on, lol.
Getting back on the original posters topic, If you have a stock spec 302 with the 30-30 cam and 11:1 compression with stock iron heads and not alot of quench, I've had good luck getting an engine like this to run on pump gas, 91 octane, as long as you keep timing under control and the AFR's are reasonable. I don't like to push it past 36 degrees total with a controlled curve, and I run the AFR's a little fat at WOT of about 12.5 AFR to keep things safe. Seems to work as long as engine temps are kept under control. These engines with dinasour heads and old combustion chambers take a fair amount of ignition lead to make power. Something in the 34 to 38 range isn't unusual, but our pump gas won't always support that, especially with iron heads.
If you really want to push it, start leaning it out a tad, and add a couple more degrees of timing, then I personally would feel better about putting a few gallons of higher octane in the tank. It all just really depends on your combo and it's state of tune.
If you haven't had the engine on a dyno you won't know for sure where the engine makes best power on timing and AFR. Each engine varies a bit. If the engine has been rebuilt you can do things like tighten quench to help fight detonation sensitivity, and other tricks I won't get into now. I turned a simple question into a very complicated answer so I'll stop before I get even deeper.
