An interesting topic the influence altitude has on jetting. Maybe not as noticeable in an auto as in a boat, but my experience was a loss of 1 rpm for every 10' of elevation climbed in a jet boat I used to own. It was a 300hp 5.7 in front of a 3 stage Hamilton pump. The principles are similar to an engine on a dyno in that it is just a pump with a nozzle (restriction) behind it to control top rpm. It doesn't care weather the boat is at full speed or jumping out of a hole shot from a stand still.
It was a Vortec with an Edelbrock carb. Anyway, at sea level where we normally run, I had the pump tuned for 4450 at wide open throttle. One of the biggest adventures I took it on was a 120km run after launching at 1000'. We immediately lost 100 rpm at WOT when launching. During the 120km run upstream, we climbed another 1000'. We lost another 100 rpm when at the top where we spent several days on a hunt. I initially was thinking maybe plugs fowling as we worked her pretty hard, but once back at sea level. it was right back to the 4450.
That boat was a beast and I really miss it.
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