CHERRY70SS Posted January 10, 2011 Share Posted January 10, 2011 The secondaries on my original quadrajet will not open runs fine in all other aspects. ls5 454 Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted January 10, 2011 Share Posted January 10, 2011 if the choke doesn't open completely, it will not release the secondary lock out, that would be a good place to start Quote Link to comment Share on other sites More sharing options...
CHERRY70SS Posted January 10, 2011 Author Share Posted January 10, 2011 choke opens as it should Quote Link to comment Share on other sites More sharing options...
stangeba Posted January 10, 2011 Share Posted January 10, 2011 You know it's not opening because .... I assume you are talking about the top (vacuum operated) plate not the (mechanical)bottom. I first thought the same thing, the choke / secondary "LOCK OUT" was holding them closed. This happens when the choke is even slightly closed. What about the vacuum brake / dash pot on the passenger side of the front of the carb, does the linkage attached to it allow for free travel? Any binding or sticking in the top secondary plate? Bruce Quote Link to comment Share on other sites More sharing options...
CHERRY70SS Posted January 10, 2011 Author Share Posted January 10, 2011 There is no binding or sticking in the linkage. I just bought this car and the carb looks as if it was rebuilt as it looks brand new. Quote Link to comment Share on other sites More sharing options...
stangeba Posted January 10, 2011 Share Posted January 10, 2011 You know it's not opening because......... low power or you can't see it open when revved up or??? I still assume you are talking about the top (vacuum operated) plate not the (mechanical) bottom. Many re builder's do a very poor job of rebuilding carbs. Just because it's a fresh re-build doesn't make it good. Bruce Quote Link to comment Share on other sites More sharing options...
mymontesa70 Posted January 10, 2011 Share Posted January 10, 2011 not sure if this helps but i had a similar problem recently . here is the thread http://www.firstgenmc.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=295755&page=1 Quote Link to comment Share on other sites More sharing options...
zmanabba Posted January 10, 2011 Share Posted January 10, 2011 I didn't see anyone else ask this. How are you determining that the secondaries aren't opening? Because 9 times out of 10 a quadrajet will not open the secondaries (the top plate Bruce is talking about ) until the engine is under load. If you are just hitting the throttle with the car in neutral there is not enough load to justify the airflow for the secondaries to kick in. Usualy the best way I could tell was by the sound (I love that roar). You should not feel the secondaries kick in when you are driving-- it should be a smooth transition. If you do feel it then that is usualy from them coming on too soon and you are feeling a momentary lean spot. There is a way to adjust the opening of the top plate--I have done it but it was years ago. If I remember correctly it involves a flat blade screwdriver and a 1/8 allen wrench. You will need to see a service manual for a better explination than I can give. This is the last thing that should be done after checking all of the other adjustments that were mentioned before. David Quote Link to comment Share on other sites More sharing options...
CHERRY70SS Posted January 10, 2011 Author Share Posted January 10, 2011 While driving there is no roar from the engine,very good acceleration but I know from owning and driving many cars with quadrajets the secondaries are not opening. Quote Link to comment Share on other sites More sharing options...
stangeba Posted January 10, 2011 Share Posted January 10, 2011 Make sure the Carb is actually opening all the way or getting "Wide Open Throttle". There could be a problem with the cable or peddle or too thick of carpet on the floor or a thick floor mat or bent linkage. With help from someone else, with the engine OFF, push the peddle to the floor and hold it there while you see if, in fact, the lower mechanical part of the secondaries are fully open, by using your hand to try to open it further. The top flap won't open so don't be concerned about that. Now that I wrote this, I want to go check my WOT to see how my new carpet may have affected it. To the rest of you reading this, have you checked your W.O.T. lately? Bruce Quote Link to comment Share on other sites More sharing options...
wallaby Posted January 10, 2011 Share Posted January 10, 2011 The Quadrajet uses both a mechanical function and a vacuum function on the secondaries. First you need to look at the base of the carb...when the engine is fully warmed and not running, move the throttle linkage to full throttle. You should be able to see the ends of the secondary shaft rotating. The secondary shaft is visible from either side, but is probably easiest to see on the passenger side down low behind the choke linkage stuff. If the shaft is rotating ok, you know the mechanical portion is working, and your attentions can focus on the vacuum portion. On the upper part of the carburetor you will see the flapper doors for the secondaries. It looks just like a throttle plate or choke plate and is there at the top of the secondary openings. It's the thing that prevents you from looking down inside the secondary throats. LOL. That flapper door is spring loaded...you should be able to push it open with your finger, and it should easily snap back closed when you pull your finger away. That flapper door is controled by engine vacuum and airflow. Under high load, the door should move to an open position as incoming air rushes past it. The door will not open if you simply rev the engine...the engine needs a load on it for a period of time before the door should start opening. The flapper door is controled by a spring which tries to keep the door closed. The spring tension is adjustable, so you can adjust it to stay closed all the time, or open too soon. There is also a vacuum dashpot on the front corner of the carb that regulates the opening of the flapper door. Tha vacuum pot normally pulls the door shut, but as your engine vacuum drops under heavy acceleration, the vacuum pot slowly looses its pull to keep the flapper closed and it slowly lets the door open. Â I suspect that you have a problem with the mechanical side of things. Look it over closely and let us know what you see. That choke interlock gizmo is the number one problem when secondaries don't work at all. Quote Link to comment Share on other sites More sharing options...
stangeba Posted January 10, 2011 Share Posted January 10, 2011 Here is a link that may help with the secondary lock out feature. Lock Out Quote Link to comment Share on other sites More sharing options...
CHERRY70SS Posted January 11, 2011 Author Share Posted January 11, 2011 It was the throttle cable not adjusted to w.o.t. Thanks! Quote Link to comment Share on other sites More sharing options...
stangeba Posted January 11, 2011 Share Posted January 11, 2011 Cool! Everyone should check this on their vehicle (including me) Bet it doesn't help the fuel economy. ha ha Quote Link to comment Share on other sites More sharing options...
wallaby Posted January 11, 2011 Share Posted January 11, 2011 Glad you got it fixed. That's a simple problem that seems common. The cable bracket tends to rotate forward where it bolts to the foot of the carb. I welded a tab to my bracket so it bears against the carb base if it tries to rotate. It's a poor design: that bracket should have been designed with two bolts holding it down. Quote Link to comment Share on other sites More sharing options...
CHERRY70SS Posted January 11, 2011 Author Share Posted January 11, 2011 Thats exactly what it is doing the bracket rotates and I am afraid to torque down on the single nut in fear of cracking the carb base. Does any one sell a better design bracket? Quote Link to comment Share on other sites More sharing options...
CHERRY70SS Posted January 17, 2011 Author Share Posted January 17, 2011 Spectre makes a throttle bracket with an adjustment to keep the bracket from rotating works perfect! Quote Link to comment Share on other sites More sharing options...
maddmann313 Posted January 17, 2011 Share Posted January 17, 2011 the best quadrajet adjustment I ever made was throwing it away and getting a Holley! Quote Link to comment Share on other sites More sharing options...
wallaby Posted January 17, 2011 Share Posted January 17, 2011 Ok, I see the picture on the Spectre website. You can see the bolt hole for hold-down on the far left...and the little screw used to prevent rotation right below it. I modified my factory bracket in almost the same way. http://www.spectreperformance.com/#CATALOG.24283 Quote Link to comment Share on other sites More sharing options...
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