The 68 350 carbs I have been using on my 350 perform better / accellerate harder with the 2ndary vacuum brake (pulloff, whatever) plugged. really I was just tinkering trying to tune the performance, and thought I would try WOT accellerations with the brake plugged, expecting major lean bog at WOT. Ends up I get no bog whatsoever. Just get up and go. Now why would that be? perhaps my air valve springs are set a little too tight?
Ken, I believe that you are refering to the Primary choke pulloff. (Its the plastic pulloff towards the front of the carb and is conected to the secondary air valve via a rod) For Wide open throttle the purpose of both the air valve spring and the primary choke pulloff is to control the rate of the secondary air valve opening. The primary pulloff can be removed but usually it requires that the air valve spring be wound too tight and greatly increases the chance of the spring breaking at the worst possible time.
Greg- yes, the primary pulloff is what im referring to. I was going to "tune" it for the fastest opening I could get without a negative effect. I just couldnt find a negative effect. I think I set set my air valve spring at just enough tension to close the flaps plus a half turn. Maybe I will back off this a little and see what happens. whats the worst that happens if the spring breaks and the air flaps flutter loose?
Folks have been doing that forever, if you get the spring tension right you don't need the brake. Here is a mod you can do to make it adjustable on the fly, though some call it a cheaters mod as if the spring is adjusted right so on n so fourth......... http://www.montess.org/airvalve.html other decent links http://www.73-87.com/7387garage/drivetrain/myqjet.htm http://www.florida4x4.com/tech/quadrajet/index.php http://www.buickpartsdirectory.com/carbs.htm http://www.amazon.com/Rochester-Car...3014/ref=pd_bxgy_b_text_b/188-8664200-4889363 http://www.google.com/search?hl=en&...et+Secondary+Air+Valve+tuning+tip&btnG=Search
Course do listen to Greg but if like JWs tells and you can't get a proper brake that works right anymore. There may be no other choice then to relay on the spring tension trick.
10-4 thanks guys. I have the right ideas in my head then. I just wanted to be sure I was thinking about it right.
I'm Kinda Wondering If Your Secondaries Are Opening Fully, With The Car Shut Off And Someone Sitting In The Drivers Seat With The Gas Pedal Floored Do The Primary And Secondary Throttles Open Fully To 90 Degrees?
When I rebuilt the carb the throttle plates were adjusted to open to exactly 90degrees, but I will doublecheck that the gas pedal opens the throttle all the way.
