I chose to advance it because it was running this badly the first time I put it together. I thought I made a mistake the first time I installed the cam, so I took it apart to verify by degreeing, so what harm could it do? The dots on the timing gears lined up the same no matter how many times I installed them. I tried moving the chain over a tooth each time, but it would never install properly on the cam.Why did you advance the cam? Are your sure the timing gears are set correctly and not off by a tooth? Did you check for vacuum leaks around the intake and carb gasket areas?
All of the above checks out. That's what got me stumped. I've set the initial timing everywhere between 7-15°, seemed to like it best around 10-12°. Having said that, it still ran horribly. It wouldn't make any power above 2000 rpms without stumbling and backfiring. Adjustments made to the idle mixture on my 750 made no appreciable difference, it would only run really rich. I went as far as to put on a fresh 600 Holley, and it ran even worse. I couldn't even get it to idle at all. Floats were right on between the two. Now the 600 just dumps fuel into the motor and floods it. The 750 is going back on. At least it ran. Poorly, but it ran.with the valve cover off, number 1 cylinder should have both valves completely closed on the compression stroke. also, the timing mark should be within a few degrees of zero on the tab and the distributor rotor should be pointing at the number 1 wire on the distributor cap.
if all of these things check out together, it should be good to go as far as timing.