For your engine to run correctly, you need to systematically address all of the things that have been mentioned to date. Start with the heat riser, it needs to work. Get the manifold hot, shut the engine off and spray PB Blaster on the shaft from both sides, let it work for a few minutes and see if you can get it to move. If you can't break it free,remove the manifolds. To get the exhaust pipe off use a little bit of heat on the flange nuts to heat them up a little. Spray on PB Blaster and let it work for a while. Use a deep well socket and try and break them loose, if they are still stuck break them off and replace them later. With the manifold off, you can soak the shaft in a solvent or go back and repeatedly work on breaking it loose. When this is repaired and replaced, start the engine and see if that was the problem.
If not, or even if it is the trouble, use your Carter YF, I have found them to be much better than the Rochester B.
Timing, Dwell and Valve adjustment are important but may not be the problem. Remember Dwell affects timing, Timing does not affect Dwell. Always set the dwell first. Follow the tune up procedures strictly from the manual and the this engine should run.
