The variables include, Timing, Accelerator pump, and Idle air bleed mix. There are plenty of ways to time these inline motors. I use a vacuum gauge. Set the timing at idle to the best(max) vacuum you can get. I don't have a timing light and with modern fuel, the timing mark(flywheel "BB") will get it started so the gauge works for me. Adjust the idle speed to about 500 RPM( a "Tach/Dwell meter is helpful). With about 30 degrees of Dwell you have checked the point gap and coil are happy together. Set the Idle mix screw to best(max) vacuum. Now we get to the "opinion" bit of the process. Set just as described, most engines will be a little advanced. It will be prone to "Ping" under load. I use a local hill and retard until it stops the "pinging". Tough to do on a set of stands. But at this point you are very close to the ideal. All that is left is the accelerator pump and maybe the power piston is sticking. Here is a good service manual:
http://c777913.r13.cf2.rackcdn.com/Rochester%20Service%20Manual.pdfScroll to page 11 to see what the power piston is supposed to do. I have found that mine needed to be "polished" with 600 grit sand paper in a drill to get it to move freely. So if the Carb has not been serviced, then a good clean and rekit should solve any remaining issues. I hope this was helpful. Set the float as described and away you should go. Some have had issues with the accelerator pump, but all of the ones I have worked on have worked fine. I would rather be lucky than good any way.
