Truthfully, you can get about as much information from seat of the pants if drive carefully. Just jet down a size or two and drive for a week. You will know pretty quickly if you went to far.
Idle adjustment only effect idle, once you open the throttle, the idle circuit closes. Adjust it lean, but not so much it won't idle under all driving conditions. In some cases if the carb is really lean, a rich idle adjustment can over come some of the stumble associated with a lean mixture.
Advancing the timing can do wonders for economy. Since we have better fuel now a days, you can run way more timing then the books say. I run mine up around 12 or 14 degrees, I believe the book calls for 8. It never pings since the compression is low, it helps the idle, and I run on the lean side. I still only get 14 or 15 mpg @ 70 mph due to the tall truck and terrible aerodynamics of a 1937 Chevy pickup, but at 45 to 50 mph the economy really jumps.
You can also fine tune the carb with different metering rod springs. A soft spring will hold the metering rod down (lean) longer. Vacuum operates the metering rod linkage, so the rod stays put with less vacuum if the spring is soft, a stiff spring over comes the vacuum quicker letting the fuel circuit go rich quicker.
Ideally you want to jet for full throttle so the engine runs its best, then fine tune the metering circuit for part throttle and cruise, and finally set the idle circuit for clean idle. Its not that easy, but you get the idea.
Joe
Joe
