Originally Posted by Zerocyde
Are you saying AirGap + Thumpr is bad all the time or just in cold weather? Truth be told I'd rather lose the thumpr than the airgap, but I'm not the most knowledgeable about this stuff yet. It just feels like I could probably find a cam that gives me just as much power as the thumpr does but with less annoying tuning and driving issues.
What gear ratio in the rear end and what tranny final ratio? It sounds like it's lugging from too high a gear /too tight of a converter.
I'd check the accelerator pump linkage, too. It has to deliver fuel the instant the throttle is opened- even a small opening needs to be accompanied by a shot of fuel from the accelerator pump discharge nozzles.
20 degrees initial should be enough for the smallest of the thumpr cams, but you can easily add timing just to see if it helps. Be sure the total timing doesn't go too high when you go to drive it normally. But for testing you can add timing by simply advancing the distributor- just don't go hammering on it like that until you reset/verify your total timing.
Are you using a vacuum advance? If you are, connect it to ported vacuum, and limit it to 10 degrees.