hey my secondaries arnt working on my 351 wit 4bbl and we hooked up the cruise controll vac line and still nothing is the power valve or accelertator pump any help will do thanks!!

 

Possibly the secondary diaphragm is bad, that is the main thing that operates your secondary, the only other thing is if he vacuum port is clogged. Power valve and acc pump has nothing to do with secondaries.

 

ok thats probly whats bad. when you run the truck with the vac port on the carb open it sucks air. do you happen to know how much vacuum i should have for the secondaries?? and are the diapragms hard to change?? Thanks!!

 

Vacuum varies with load, there are 3 screws and one c clip, there is also a cork gasket between the main body and secondary body, 4 screws for the cap, take the secondary off, remove top, the diaphragm comes out, but watch for a small steel check ball , its better to disassemble right side up.