Your distributor should have a vacuum advance, but it may have been removed. There will be an opening in the side of the distributor for the vacuum advance if that is the case. The original distributors had trouble with the breaker plate connection to ground, and also with shaft bushing wear. Both conditions would cause varying degrees of low-speed engine roughness off-idle and/or when the vacuum advance actuated. Someone may have removed the advance control as a remedy, but leaving the vacuum line off would do the same thing. Neither was a proper repair for the problem- it just covered up the problem.
Your off-idle trouble could be either inadequate accelerator pump discharge, or distributor trouble. Remove the air cleaner, and with the engine stopped, open the choke and work the accelerator linkage for about half-throttle. You should see a strong squirt of fuel as soon as the throttle moves.
Harvester
