Vacuum leak? crossed plug wires? i find that going back to the last thing I did leads me to most of the trouble I have. If not first thing I'd do is check the chain and balancer. If the timing mark bounced around a lot when you set the timing the chain is probably worn. Turn the crank until the rotor moves,notice how far you have to turn the crank before it moves when turning the other way.To see if the timing mark on the balancer has slipped(common on slants). Thread an old spark plug for a bolt you've ground round on the end or buy a positive stop,run it in #1 spark plug hole and turn the crank BY HAND(breaker bar is OK but don't use the starter) until it stops. Mark the damper with a piece of chalk or paint at a reference point on the timing cover(usualy the timing tab,turm the crank the other way until it stops and mark the damper again. The place between the two marks is TDC on #1. This is where the "0" mark on the damper should be. If so you're done. If not remove the stop. While you're turning this anyway you may as well check the condition and gap of the points. Make a mark halfway between the marks you made,bring the mark to the timing tab at the factory setting turning the crank clockwise. At this time the points should be starting to open with the rotor pointed at #1. If not grab the test light,make sure it works,set it aside . Turn the Dist. in the direction of rotation until you're sure the points are closed,turn the ignition on and check the Neg. side of the coil(the one that goes to the Dist)for power. There should be none since the points are grounded. Turn the Dist. against the direction of rotation until the test light lights. Your timing is set,lock 'er down.
If nothing shows here it's time to go after the carb
Ron