secondaries won't open on holley 3310

Did anybody mention;
that if the gas pedal is not opening the primaries all/ or almost all, the way, the secondaries can't get signal, and the link-rod will be locked out?
Or if the cam-timing is out too far, then the pistons are gonna push a heap of AFR back up into the intake, slowing the in-rushing air to a crawl, reducing venturi-vacuum?
Or that if the exhaust is severely restricted, the overlap cycle will also pump up the plenum?

The point is this;
You have proven that the secondaries are working on the bench, so..... it has to be a mechanical issue outside of the carb.
Baring that, the same symptoms will manifest if the carb is pig-rich.