I have my Quadrajet off of my engine to rebuild. I know that quadrajets have vacuum secondaries but does that mean the secondary throttle plates should open fully with just the linkage? Right now, if I move the mechanical linkage all the way back, the primaries open all the way but the secondaries do not. Will they open when there is a vacuum? Thanks
Agree with Quenton.. the secondary air valves open on air demand. There is a spring and hex head screw that set the tension for those valves. They were usually set around 5/8ths of a turn from when the spring first makes contact with the shaft. Would highly recommend getting Cliff Ruggles book on Quadrajets. He also sells the best rebuild kits in my opinion.
You have to bend the linkage, IIRC, to make the sec throttle plates open all the way(verticle). Most of them were designed not to go verticle from the factory to limit the secondaries effectiveness.
So I just went to the guy rebuilding my carb and had expressed my concerns and opinions regarding the secondaries.
Right now the carb is off the car so we are turning the linkage clockwise by hand. When opened all the way the primary plates open to 90 degrees and the secondaries open to 45 degrees or so. The small stop on the linkage hits the carb when it is fully opened and prevents any further movement HOWEVER you can manually pull the rod that connects the primary and secondaries and than they will open to 90 degrees.
It was explained that the engine vacuum will open the secondaries to the 90 degrees under WOT. While I have my doubts we will find out when we dyno.
Is there a possibilty that he is correct? How about the carb for the firebird being desgined not to open all the way? Is that what I am se
It was explained to me that the vacuum from the engine will pull th
What year carb? The 1st gens had a limiting tab to prevent the secondaries from opening all the way to meet HP vs wieght mandates. The FB drivetrains are the same as GTO's. GTO's where heavier, so they didnt have the tabs.
It won't...the linkage that actuates the secondaries can be bent/adjusted. This is explained in Cliff's book. Mine only opened up to about 45 degrees. After I adjusted the linkage(bending)to get the full 90 degrees, there was a noticeable difference in throttle response. As stated before in this thread, depending on the model of car they were installed on the secondary linkages were limited due to emissions regulations yada yada...I'd find another carb rebuilder.
Vacuum DOESN'T open the throttle plates. The linkage does.
Vacuum has some control over how fast the air valves(the top butterflies) open thus controling air flow. It will not change the angle of the throttle plates.
