is the hei bad?

[hdck07]

I am getting a 72 back on the road after about 15 years of setting. It was my grandpa's truck, he was the second owner when he bought it in 81. It has a 250 from a 72 nova, three speed on the tree. So far it has got a new clutch, new rear end (even though it is 6 lug) new u-joints, new carrier bearing, and carb rebuild. I put a hei from a later pickup from a junk yard and never could get the timing right. The timing light wouldn't work right, I can't really explain it, I could get it running fairly smooth based on sound but, vacuum was only about 15 inches. When I would hook up the vacuum advance (I hate calling it that, should be vacuum retard) it would pop, snap, and back firing. I go back to the points and the timing light works, vacuum is up above 20 inches and vacuum advance works like a charm. I can't figure it out, I thought that hei would work or not, no in between. Should I try another junk yard one or go with something new? Sorry for the long story, no pictures to post. It will be on the road soon as my driver, rust and all. Picture soon.
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