I have a 1985 z28. I have a 4 barrel carb. When my car is parked and I give it gas the secondaries don't open. Is that suppose to happen? Or do I have to have it in gear in order for the secondaries to open?

 

it depends on your carb type, mechanical or vacuum secondary's?

 

I believe it to be vacuum. But can you tell me what both would do if the car is in park and I'm giving it gas.

 

The Vacuum type will not open unless you are driving, the mechanical type will open anytime the throttle is pressed beyond the preset point.

 

Thank you. Most automatics I believe are vacuums. Is that correct?

 

No, it can be which ever you want, i had a Vacuum before now i have a mechanical, the mechanical is just more predictable, the vacuum secondary only open when the engine needs the extra air&fuel

 

Thank you

 

Most likely you have the stock quadrajet. The secondary opening is controlled by two things: 1) the throttle blades on the bottom of the carb that are opened by the throttle arm; and 2) "air valves" on the top of the carb that are opened when flow demand is high enough.

Most likely you're looking at the top of the carb and seeing the air valves not opening. They are controlled by two things: 1) spring tension (which is what makes them shut); and 2) vacuum via what is often called the "choke pull-off" on the front corner of the carb, called "vacuum break" by the factory - there's a link that goes from that vacuum can "choke pull-off"/"vacuum break" to the linkage for the air valves; until vacuum drops enough to release the pull on the pull-off, the air valves won't open.

All that to say, no, blipping the throttle in the driveway most likely won't open the secondary air valves. They are adjusted to keep too much air from going through those huge secondary venturii until fuel flow can catch up through the secondary metering system to support the increased air flow.