My 350 is a bit wierd. It has a 327 2bbl manifold on it, with single point ignition and externally resisted coil. When I tried to time it to 10-12 degrees from TDC on #1 it ran ok, but I had a bad stumble on acceleration even AFTER I rebuilt the carburetor. I ended up advancing it a few degrees more to get the stumble out. It's as about as far as I can get away with. Now it's at around 15 which is pretty damn high (I had to move the spark plug wires over one terminal on the distributor to get the clearance between the vaccum advance and the intake manifold upper passage!). That was the only way to get the stumble out. I've got great low-end power, but it's inneficient gas wise. I dirty my plugs up pretty badly. Also at idle it sounds like a drag engine.
