It's hard diagnosing engine problems "over the phone", but is it possible that someone had this engine apart in the past, then just stored it, possibly because they couldn't get it to run? The reason I ask is that if the ignition points break when the timing mark is centered in the timing inspection hole, if you know you are getting spark, and if you had lapped the vales and are sure they aren't leaking, then maybe....just maybe...someone had the camshaft out and didn't properly index it when reinstalling it. No amount of carburetor or ignition timing fiddling can compensate for that!
