Retarded ignition timing will cause a hesitation similar to a weak accelerator pump but it's way easier to fix. Check the ign. timing as per the book at whatever RPM it specifies AFTER you set the points making sure there is no mound built up on one of them. If ignition point files are still available, buy one and dress the points down before you check the gap. Also as someone mentioned, note whether the vacuum advance works -- the distributor will move and hold when you blip the throttle.
It the timing is retarded for whatever reason you will overheat the exhaust manifold(s) and fry the gaskets, which will result in nasty and annoying exhaust leaks and all the hassles associated with replacing the gaskets -- like broken studs.
Quite a few people have mentioned vacuum advance, but my distributor doesn't seem to have any vacuum ports. I did some research and it looks like the vacuum advance diaphragm is a separate unit. Is it possible mine was removed for some reason and never replaced? I also don't have any spare ports on my intake to feed a vacuum advance.
