Be very careful about not getting that adjustable main jet too lean. Once the fuel/air mixture gets much below that ideal 14.7:1 (stoichiometric) mixture, combustion temperatures spike into the range where engine damage happens very quickly. One night we had a MOPAR 440 tractor pull engine on the dyno, making a final torque pull at 6500 RPM. Apparently, a bolt near the middle of the intake manifold had loosened up for some reason, and one cylinder went very lean due to a vacuum leak. I heard a very slight rattle from the engine, and before I could back off the dyno load and chop the throttle, that piston got a half dollar sized hole burned into it. Of course, the RPM/Torque calculations we made after the fact on that run yielded 714 HP running one 4 barrel carb and gasoline, prior to adjustment for temperature, pressure, and humidity. At those power levels, things happen very quickly.
Jerry
