Quadrajet not working properly

[itsnicyo]

When I bought the car I knew they weren't the fastest, but I this car was on a whole other level. Pretty sure my girlfriend's Camry can beat me right now. Think I found the problem, I don't see my secondaries working. At the last minute they start to kick in a little.. but not much. Where do I start to fix this problem? I posted a video below so you guys can check it out.


https://www.youtube.com/watch?v=Ea3a7dm ... ata_player


[youtube]https://www.youtube.com/watch?v=Ea3a7dmlyEQ&feature=youtube_gdata_player[/youtube]

 

[crotchss]

Can't watch your video, says it's private, you need to change video viewing restrictions.

 

[tetomas]

Cant see the video, but the secondary air flaps will not open most of the time if you are just revving it up in the shop. Have you checked all the basics, timing, fuel pressure, etc? Another thing to check is with the engine off, open the secondary air flaps by hand, look down the carb while opening the throttle to make sure it is opening all the way. I have seen the secondary throttle blades hang on the edge of the intake, or an incorrect gasket, or just carbon.

 

[itsnicyo]

sorry about that, the video is now public.

 

[crotchss]

Tetomas is right the secondaries usually don't open while revving in park. The secondaries open through airflow of the air flaps, and they appear to be working. Smaller engines don't require as much carb and will open later.

 

[techg8]

In the video when you held the air flaps open it looked like the secondary throttle blades in the baseplate didnt really open much. I would start there.

As mentioned, check for gasket interference as this can jam them up.
Also, check the secondary lockout lever on the passenger side between the carb body and the choke unit. If the choke linkage is off just a little, this can block your secondary throttle blades from opening.

With the secondary air flaps held open by hand, you should be able to SEE the secondary throttle blades open 90 degrees when you jack the throttle hard. In the vid, they barely moved.

 

[565bbchevy]

I would start by verifying your linkage is set up properly getting full extension by having someone watching while you are in the car pressing the pedal to the floor (with the engine not running) you could also set it up to take a video of the linkage if no one is around.
Also while looking down the carb like your video (again with the engine off) verify the rears are opening all the way with no binding or drag by manually opening them.
I'm believe typically the rears on a Quadrajet will open more when under load while running rather than in park.

 

[itsnicyo]

Thanks I will try that out! So do the secondaries run off of a vacuum and that's why it takes a load for them to work?

 

[techg8]

well the secondary throttle blades are located in the baseplate and are actuated via a link to the primary throttle shaft. These are what open mechanically when you hit the gas pedal.

The secondary Air Flaps are located on top of the carb in the air horn and YES these are opened and controlled via vacuum. When the secondary throttle blades are mechanically opened, Air at atmospheric pressure wants to push past the upper air flaps to get into the engine. The flaps have a spring that holds them back a little and keeps them from flapping, but what really controls the "release rate" of the air flaps is the primary pulloff which responds to manifold vacuum.

When you floor the gas pedal the secondary throttle blades open fully and manifold vacuum drops quickly. this in turn releases the primary pulloff which, through its link to the air flap shaft, controls the release rate of the air flaps to prevent a lean bog from opening too quickly. IF there were no primary pulloff and a loose air flap spring, the air flaps would spring all the way open immediately, causing a lean condition and a bog.

 

[itsnicyo]

Okay, I took a look and I don't think my secondaries are opening enough. Took another video, gotta love technology these days


http://youtu.be/xa5WfzkgF3w