Ford vacuum advance

[clutchdust]

I have helped a friend with a couple older Fords he's had over the years. One was a Mustang with a 351 Cleveland and this one is an older F-100 with a newer 302 in it. Even so, they're both carbureted and non-computerized. In both instances I set up the timing with the vacuum disconnected from manifold vacuum. But both of them run like crap with the vacuum hooked up. I have found they actually run better with the vacuum to the distributor capped off.
I have got to be missing something here. Does Ford run advance on a different principle from GM? Why the hell am I struggling so much with these?

 

[TimAT]

You can't tell? Look at the front of the car. They CIRCLED the problem.

 

[clutchdust]

I've been telling him that for a couple years now but it's just not getting through. Of course, this is the French guy.