i have noticed that my 455 is picky about when it lets the secondary doors open. what can i do to tune this for the most power and have it kick ass again. this is the third rebuilt q-jet going on this thing and im still not happy, let me know, thanks
1. Production line rebuilt carbs are often junk. It's no wonder you needed three. The only thing surprising is if you actually get a "good" one. 2. Air valve is tuned by the spring (only) on some early carbs; by the spring and the restriction in the choke pulloff on later carbs; and VERY early carbs had a goofy dashpot thing cast into the air horn--but it's very unlikely you'd ever run into one of those. First Guess: you need to verify the spring; and you need to check the choke pulloff. A larger orifice (less restriction on the choke pulloff) means the air valve opens faster.
there are several items that can be tuned or tweaked in the secondary system. the best thing to do is pick up a quadrajet book and read up on the system. the cliff ruggles book seems to be easier to understand and has more pictures. a big item is with the engine warmed up but TURNED OFF, have someone sit in the car with the gas pedal floored and check to make sure the throttle blades are open fully. you would be suprised how many people never check. good luck
1. Compress the vacuum diaphram, hold your finger over the hole where the vacuum hose plugs in and let go. It should take about 2 seconds to fully release. 2. With allen wrench and small screwdriver, release the spring tension on the door and reset at about 1/2 turn of tension and if it bogs, add 1/8 more turns until bog stops. Should be OK by 3/4 turns or look for another problem such as timming, float level, accelerator pump, etc.
