I run a 750 SD w/vacumn secondaries on my 427 FE , I have gone from 850 holley mechanical to 750 SD mechanical to 750 SD vacumn, Berry Grant finished what holley started, the vacumn carb has no problems at all, it starts fine, a little to much foot still lites the tires
, hard 1st to second shifts still raises the left tire off the ground a bit
, you still DON'T nail it in the turns, and while crusing I'm getting 4 more mpg, in short other than the mpg I don't notice any difference. Don