When setting the timing on a 1950 flathead six do I disconnect the vaccum line from the distributor? The engine has been rebuilt and I see two marks when using a timing light. It starts great but misses when accelerating and has no top end power.

Also, in order to make sure the distributor is in the correct position. Must I find TDC on cylinder 1, remove the distributor cap to verify the rotor is pointing to the correct location?

 

Yes you have to remove the vacuum line at the distributor. It is best to cap the line as well. Timing should shoud be set at idle (450 rpm) and it is set at TDC (0 degrees) The 2 timing marks are there because there could be one of two seperate harmonic balancers used on the 226. You use the timing mark closest to the outer circumference of the harmonic balancer. (one of the harmonic balancers used has a bigger diameter than the other. It is fairly easy to tell which is the correct mark.)