Not sure that writeup is factually accurate. I called Edelbrock. 1405 and 1406 have extremely minor differences. Primary and secondary venturies are identical as well as boosters. Primary jets are 0.98 and 1.00 - a 2% difference in flow area. Secondary jets are identical. Metering rod is the same diameter but slightly shorter on the 1405, which makes the carb run leaner. So slightly leaner primary jet on 1406 and slightly leaner metering rod on 1405, which makes both carbs essentially equal out of the box. And for $5, I can change the primary jet on the 1406 to make it identical to the 1405. Or for $75, I can put an electric choke on the 1405. Don't forget at altitude, engines run rich unless jetted down. And just for information, higher compression does not flow more air. Bore and stroke do not change. It still pulls in 318 inches of air per combustion cycle. You still need a 13.8:1 air to fuel ratio - same amount of air and gas.
