HELP! Slant 6 just doesn't want to go!

Sounds like a problem my Scamp had when I got it. I took it'd run for a few minutes then die, no matter what I tried. I figured it was a fuel issue so I put on a clear fuel filter just before the carb and I started the car and let it run awhile, after a few minutes I watched as the fuel level in the filter dropped and sure enough, the engine sputtered and died. I worked and worked trying to figure out the problem but couldn't I didn't know as much about engines then as I do now (still not near enough) so I took it to a mechanic. Long story short, he fixed it. Said it was a diaphragm located under the distributor? Said they get brittle over time and tear and that's what was wrong.. Any affirmation on this would be great! Good luck!