You see what yur doing here?
You are trading transfer slot fuel for mixture screw fuel and twiddling the speed screw to make it work. This is normal. And it's a good thing that you started with 12* of timing, because by 18* it won't work any more, the transfers will probably be too far closed. Now you can probably hook the Vcan back up...... to the SPARKPORT,this time,lol. Then rev it up to 2200 to 2600 and see how much Total timing you have WITH the vcan.
As for loading up; something ain't right. I had a 292/292/108 Mopar cam,that would idle down to 550 with a clutch, and it pulled itself along in 10.97 starter gear, at 4mph like that; on flat level, hard pavement. To do this I had to dial back the idle-timing from 14 to about 5.
What's yur water temp; mine was 207*F
