Alright, I know very little when it somes to carbs. I recently put a full exhaust system on my car, got rid of the smog equipment. And now for some reason the 4bbl doesnt always open up. It seems that it opens up about 1 out of 10 times. Its been driving me nuts, it opens fine if you just tap it with your hand, so it seems that the choke must be holding it shut or something. But once again sometimes it does decide to work. I really need help on this, I really dont wanna go get a edelbrock performer carb.

 

Make sure the choke is opening fully (is the wire to the choke heater element properly attached?). The choke has a linkage that prevents the secondary throttles (not the airvalves on top) from opening. If the choke doesn't open FULLY it will prevent the secondaries from opening when you nail it.

 

Im a complete idiot when it comes to this stuff, so. The choke opens at full throttle, or just once its warmed up?

 

The q-jet secondaries are controlled in two ways: 1) the throttle blades opened by the accelerator cable, and; 2) the air valve on the top of the air horn which only allows as much air flow as the engine can handle.

The choke is involved keeping the secondaries from opening in two ways: 1) there is a lock-out mechanism that keeps the throttle blades from opening until the choke is fully opened, and; 2) the choke pull-off (vacuum break, the factory calls it) that holds the air valve closed until vacuum drops. The first mechanism is to keep you from killing the car with wide open throttle operation while the engine is cold, the second is to prevent "bog" when you first floor it (after the engine is warm).

Sitting in the driveway blipping the throttle is not a proper test for secondary opening. If that's what you're doing to come to your conclusion, don't worry about it. Make sure your choke is operating properly, and do the tech article adjustments to get the secondaries to operate at their optimum.

 

The choke should open fully by the time the engine is warmed up- has nothing to do with throttle position. However, it's heated electrically and if the heating element inside is going bad or you just leave the wire off the choke element that supplies the power it'll never get fully open. The lock-out linkage to the secondary throttle shaft won't disengage.

 

Well I let the car warm up, and the choke was holding the secondaries shut still. I dont understand though why it would only do this some of the time, also when I checked on the connection it seemed that the part the wire connects to was coming loose, I pushed it back in and pushed the rivet back in with a wrench. Could the choke be damaged, making it not work correctly all the time, but working right sometimes?

 

well it was the vacuum break, I unhooked the hose from it and plugged it for a temporary solution. Havent gotten to drive the car yet though.

 

That wasn't a "solution", you just disabled a vital function.

Hook that vacuum line back up to the vacuum break. It is supposed to hold the air valve closed - did you read what I said above? Without it, you'll bog when you go WOT.

The secondaries shouldn't open while blipping the throttle in the driveway on a properly functioning q-jet.

 

The problem was the secondaries werent ever opening. Not when driving down the road or in the driveway. Either the electric choke or vacuum break is screwed, atleast thats what Ive come to believe, course then again Ive never seen a qjet operate correctly on any car.

Edit: Im just gonna swap the carb out to an aftermarket, I know the stock carb can perform fine, but the problem is it isnt. And I dont want to waste my time on it anymore, its been messing up the whole time Ive had the car, and I have no reason to believe that it will last even if I rebuild it.

 

Try this: Take the air cleaner off and plug the fitting for the hose that goes to the air cleaner. On a clean paved road with the engine fully warmed up, floor it - do you hear a "bwaaaawwwww!" If you do, the secondaries are opening.

If you can feel the secondaries open, you're bogging. If you don't feel them open but hear the "bwaaaawwwww!", they're opening and operating just as they should be.

 

Ok, when everything is hooked up as it should be, secondaries do open...occasionally, about 5-10percent chance of em opening at wot. I dont understand why it does it, but most of the time when I put it to wot they do not open, I can feel the difference a hell of alot, with the secondaries it lays a strip and chirps second, without, it just kinda sluggishly moves at about half the pace.

Edit: The vacuum break was holding so much that I could barely pull it out at all with my hand, I think thats the main problem, but if it is I dont see why the issue would be so inconsistent.

 

Sitting at idle, you shouldn't be able to pull the vacuum break open. When you go WOT, the vacuum drops enough to release the vacuum break.

More likely your lock-out latch isn't disengaging, and that's usually because the choke isn't opening completely or the high idle cam isn't dropping all the way when the choke opens. Make sure all of that stuff moves freely with the engine off and throttle held open slightly. Personally, I just leave that latch off when I put a q-jet back together; I know my car and I'm not going to abuse it when cold, and without it there I don't have to worry about whether or not it's released when I "need" WOT.

 

take that rod off unless you are one of those guys who hits the gas when it is way too cold

57 is a buy the book type of guy and there is nothing wrong with that

me I try it all different ways to get the most out of stock parts

that rod that goes from the secondary airhorns to the rear pass side of the carb is useless in my opinion.

there is also a arm at the bottom of the choke assembly that wont let you open the sec throttle blade unless the choke is fully open

in my OPINION that is too much restriction

let me state that agian MY OPINION

 

Don't think he meant to remove the rod that runs to the air valves, just the lever that locks them out until the choke is warmed up. Removing the rod would also disable the vacuum break function which IS vital to proper transition into secondaries.

 

I, too, thought the rod going from the vacuum break to the AV was useless. By the time I figured out my bog could not be tuned out by the AV tension spring alone, I could not find that rod again.

Unless you go through very precise and involved modifications, the vacuum break is the only way to avoid an initial too-early opening of the AV. If you know how to go about that, more power to ya, but it ain't gonna happen giving instructions over the internet to someone who doesn't already have extensive q-jet tuning experience.

 

no I ment to remove the rod

maybe I sould not suggest these things to the begginer

I have been foolin with q-jet for quite a while