Preaction,
In my experience, more advance means more run on in high compression engines. So no, this would only exacerbate run on. The late 60’s and early 70’s were the ragged edge of “run on”. The Boss 351 engine and the 429 Cobra Jet 429 were great examples of run on. The factory engineers installed an electric solenoid to “hold” the hot curb idle speed. When the key was shut off the solenoid retracted closing the throttle blades completely close. This stopped engine run on in these “emission controlled” engines that were on the ragged edge of lean to meet standards, yet have performance.
The relationship of the throttle blade to the transfer slot is a bit “ambiguous” to say the least. An oil film will be formed on the throttle plate to “kinda” represent the line of closure so to speak. Using a light below and into the throttle body relationship is helpful. If you have the carb upside down you can see the “edge” of the throttle blade on the throttle body/plate. It should not be above the throttle transfer slot completely nor below it. After some visual you will get the feel of its relationship. This adjustment that can be controlled by initial timing on a ported vacuum engine and if a 4 barrel the secondary throttle stop screw can be critical to controlling engine run on. And if your air mixture screws do not affect idle, you may have the blades to high or to low.
But more initial advance will exacerbate run on, even on a properly adjusted carb. Especially on the above mentioned engines. And other high compression engines of that era of extreme “leanlessness”. Of note the 429 Cobra Jet of 1971 used a Rochester QuadraJet to achieve “emission standards” of the day. To my knowledge the only time a Rochester Carb was install on a 60’s performance Ford. And it was equipped with the electric solenoid to shut the throttle plates. The 429 “Super Cobra Jet” was exempt from this emission standard and ran a Holley. I guess related to its performance category.
What engine are you talking about? I may need to open a thread on carb/timing adjustment and other factors on 1967 to 1973 Ford engines. I have found many interesting tidbits over the years.
Rob