750 Holly Carb question wheres the 4 barrel

[darrin75]

This may sound dumb, but I am not an engine guy.  What is the difference in vaccum secondary 4 barrel and the regluar four barrel.  The reason I ask Is no I could push the gas to the floor and the secondary car or 2 other barrels would not open up at all.  The throttle cable has been move , adjusted back and forth no difference.  Its no even close to opening up the other 2 barrels.  the only thing I could do was make a bend in my little metal rod and make it shorter.  So that the small rod used to turn the shaft to open the other barrels would work.  I may have to take pics to show what I am talking about.  By no means am I a engine guy, but got to start somewhere?

[Ghoste]

A vacuum secondary does not open until engine vacuum is at a specific level and then the vacuum signal inside the carb and going to a small canister on the outside of the carb, allows that cannister to open the secondaries.  A vacuum secondary carb will not open the secondary just by manually opening the carb with the engine off.