Try bumping it into neutral when stopping and then back into gear when taking off (Did it for years for the same reason IE: converter to tight for the camshaft)Yeah, doing that too. Not the most elegant, but it gets you there.
using manifold vacuum for the advance will aggravate the low speed drivability as the advance drops out when accelerating and does not return until cruise. The ported vacuum should climb and add more advance until the throttle is opened beyond a given point. by that time your mechanical should be taking over. Hope this makes senseNow THAT is an interesting idea. I'll try it tomorrow.
Results: with ported vacuum driving the vacuum advance, throttle modulation off idle is MUCH improved, and the need to brake torque at stops is reduced (though not eliminated). Manifold vacuum is 15" at idle, ported vacuum is 12" (this is with the throttle blades completely closed). When the throttle is opened, both drop, though manifold vacuum drops much more than ported does, probably because the ported side has all of Earth's atmosphere to suck on. Both vacuum levels then increase as engine RPM increases (all this is with no load). The spark advance is thus not being retarded so much off idle when using ported vacuum, and so it makes sense that power comes on more gradually. That was a very insightful suggestion, thanks!
I have also noticed a "chug-chug" mode when starting warm without opening the throttle- there isn't enough vacuum to advance timing, so the engine chugs along like a steam engine at low rpm until it either dies or you open the throttle a little, which develops vacuum, which advances the timing, and then the engine idles smoothly with the throttle closed. Is this why they had throttle stop solenoids "back in the day"?
Carb numbers are 3437S front and 3858S rear. The dies used to make the stampings are very different, so I suspect they are not of the same vintage.
Now if I can make it smoke a little less...
