Ok so I am almost done with my camshaft install, and I pop in my Demon Carb. Installation video just for kicks, and the guy takes the throttle linkage and says that the secondaries should open all the way when pulled open to full throttle, and if not the carb is messed up. I have a Vacuum secondary carb, so would the secondaries open with the linkage pulled to open throttle, BECAUSE IT DOESNT!!! I thought the vacuum is supossed to open them, but the guy on the video didnt say for only Mechanical secondaries or anything like that. IS THE CARB BROKEN???? Need to know ASAP the car should be done tomorrow and i want to drive it!

 

No the carb is not broken. They mean the throttle plates should open all the way when at WOT. Open the secondaries air valve (ie, top plate over the secondary bores), and look down the bore. Then open the throttle plates all the way (ie, pull the carbs throttle linkage all the way open), and watch as the throttle plates open.

I think you got confused; mistaking the air valve door over the top of the secondaries as opening with the throttle linkage, which it does not do. The secondary airvalve door opens in response to engine's demand for additional airflow.

Dave

 

The guy in the video took the throttle and opened it and then shows you the bottom of the carb as both the primaries and secondaries open all the way up, Mine doesnot open the secondaries. I am looking from the bottom of the carb plate, not from the top, Its not on the engine yet.

 

Then I'd suggest you have a problem.

Dave

 

You have no problem. On a vacuum secondary, the rear blades are opened by the vacuum secondary diaphram, not directly by the linkage like a double pumper.

Look on the passenger side. You will see a rod come out the bottom of the secondary diaphram going down to the secondary shaft.

 

You're right, I was thinking Q Jet.

You can open the secondary throttle blades on a Q Jet manually. Its the air valve door above the secondary bores that needs engine load to open.