I have a factory setup on my cc carb on my 85 bird with a 305. I recently had the carb rebuilt at the local Chevrolet dealer, and I realized that it would then flood out while idling. Just shooting in the dark, I turned the screw on top of the choke tower, and that seemed to stop the idle problem, but it still seems to be a little rich. Question that I have is : What is the proper adjustment for it (on the choke tower) and will no belt on the air pump cause this??? air pump works and system is all in tact, just took the belt off to free up a little power, but it can go back on if need be.

 

what screew are you talking about there shouldnt be any screew that will adjust anything on top the choke tower anyways there should be to small a/f screews under where the fuel enters the carb basically make your engine idle way down by turning the idle screw should be located where the thorottle hooks up to the carb but once you get it down to say 4 5 hundred you can start adjusting the a/f screews with the motor off take and see where ther at by counting the turns in on both of them then take an average of that and set them both to that spec this will put them back in sync with one anouther ok now start the motor take and tun the screews in 1/4 turn at a time on both sides untill you notive the cars idle starting to drop then rase them up untill you hear it coming back up at that point set them open anouther half turn to make sure you dont run it too lean so now both screews should be in snyc and car should run perty good hearing the motor change to what your doing is the key here so thats why you make it idle so low you sould get it to idle as low as possable with out dieing you may have to start it a few times but thats how i have set them for years

 

as far as the air pump the belt off wont affect anything but with the belt on you really dont lose any power it takes nothing to turn the air pump

 

https://www.thirdgen.org/newdesign/tech/quadrajet.shtml

click that good artical on cc q jets

 

Sorry, Maverick, I'm afraid you're way off base.

The adjustment in the choke tower area is the idle air bleed. It is adjusted using a dwell meter on the 6 cyl scale, connected to the green connector in the harness over by the A/C that doesn't connect to anything normally.

Start with the idle screws in the base that Maverick talks about turned out about 7 turns each (both turned out the same amount). With the engine fully warm and idling, adjust the idle air bleed in small increments, allowing the ECM to adjust after each movement. Shoot for 30 degrees dwell.

Just curious, if the dealer rebuilt the carb, why didn't they adjust it properly? If it is truly "flooding", then it's more than the IAB adjustment.

Oh, Maverick was correct about the A.I.R. being disconnected not affecting this. You were correct thinking that taking the belt off would "free up a little power" - however, it was actually very, very little, and you've risked ruining the pump by not having it running (the check valve will leak and allow exhaust back into the pump, which will freeze it up). I documented 1/4 mile times with and without the belt on the pump - made less difference than run-to-run variation, and when I went to put the belt back on the next week, the pump was frozen up.

 

THANKS GUYS!!! thats alot of help...gives me something to go on. I think the I/A screws have plugs over them, but I will double check that...gotta be a way to get them out.

The dealer rebuilt the carb as part of the deal on the trade. I had a 95 Camaro 3.4 V-Sux w/and auto tranny, ttops, and 140k miles on it. this bird was sitting on their lot, and I wasnt about to pay someonelse to rebuild it, so I had them do it. I'd rather get it set right myself and know how and where it is set as I would let them screw it up even more.

good info on the air pump. THANKS!!! didnt know that, but its good to know. If its not locked up, I'll let it be for a while.

 

he is right about the carb i totaly space it last night on anouther note having the air pump hooked up has a big advantage that being your valves expesaily your exhast valves will last a whole lot longer

 

How does that work?

Ben

 

forceing air into the exshast helps cool the valves so there for they dont burn up as quick so there for they last longer and stay clener

 

Can you give a more detailed explanation? I wouldn't think that air injected into the exhaust after the heads would have any significant effect on the valves.

EDIT: I meant to say the A.I.R. system, instead of saying air injected into the exhaust after the heads because that's too general.

 

ok forcing air into the exhast moves the heat from the heads exhast ports down the line to the cat on think about it if you.... ok example you take and pre heat your oven to say 350 degrees you open the door were does the heat go it rises right but alot still stays in the oven becuse theres noting pushing it out ok now take and put a fan in front of the oven and turn it on facing away from the front of the stove its going to suck the heat out of the oven and push it on down the line same thing works in exhast the air you push into the manafold takes and sucks/blows the heat farther down the pipe there for your valves dont get as hot let me know if you need more on this subject if you think about it why shouldnt it work its one of those plusses to emissions junk i have seen the efects of it taring down motors day in and out the ones that run the air pump look a whole lot nicer than thouse that dont but this is just my input

 

oh yeah forgot to mention that they stay cleener becuse.... ever car has backpressure that mean that you exhast is trying to enter the motor again when the valves open expetially if you have any sort of cam that has duration and over lap ok say your air pump is hooked up and you have a working cat the hotter you get the cat whitch is what the air pump is intended for the better it burns the crap out of the exhast gas ok so you cat is working good your carbons in the exhast are down witch meens less junk in the gas trying to enter the motor

 

these are just the pros to some of the emmitions crap there are allso cons of it me my self im not running any emmistion on my bird as for my cat got plugged becuse my air pump froze there for i have a hollwed out cat and all air tubes pump and relation removed

 

1) At least on 3rd gens, the A.I.R. is only routed to the manifolds while the engine is cold and the ECM is running in open loop. In the life of a vehicle, that is a very small amount of time that the A.I.R. is routed up next to the valves. The rest of the time it is going way down stream directly to the cat.

2) The amount of air injected by the A.I.R. system and the velocity at which it is moving are so small that it will have next to no effect on the direction of flow of the exhaust. It's simply there to provide more oxygen to the mix to aid in the combustion of fuel that may not have been burnt in the cylinder.

3) The cat is so far away from the exhaust valves that any claim that a "cleaner cat" will prevent reversion of junk back through the exhaust valves is simply ludicrous.

4) Claims that lack of A.I.R. leads to plugged cats are also ludicrous. I have 3 GM vehicles, early 90's models, that have a cat and none of them came from the factory with A.I.R. How, oh how did the factory keep those cats from plugging without A.I.R.????? (All of them have in excess of 140k miles and pass the dyno emissions test with ease - with the original factory-installed cat.)

5) Most of the deposits you see in an engine are from oil. Poor maintenance will lead to many things, amoung them failing emissions systems and additional oil usage. Oil doesn't burn nearly as readily as gasoline in a spark ignition engine, plus there are more things in oil that aren't intended to burn; so when the oil isn't changed regularly and allows wear, for instance, one effect of which is to allow oil where it isn't intended to be, more deposits are formed. Valve guide wear and deposits will eventually lead to improperly sealing valves.

No intent to flame, but your contention that A.I.R. is good for valves is borderline silly. Sorry to be so frank, but that's the truth.

And, it's a pretty long stretch to relate all this discussion to the question posed originally in the topic.

 

Just a note. They do use a different kind of cat for the cars witout air. The older cars that had air origionally need it for the cat to work properly while the newer ones with the other kind of cat dont. I have heard of people going with the new style cat to get rid of the air pump though.

Ben

 

thank you for saying that momar i was just going to type that all out

oh as for the valve guide inproper seeling vavles it would take a hell of a lot of wear to make it not seal like the guide would have to allmost be gone for that to happen and its not the valve gude that keep the oil out of the motor its the valve stem seal that acually does the work and it dont care if the guide is worn out to make the seal if your getting oil in the combution camber it can only come from a few thing like hardend valve stem seals, faulty rings, stuck pcv valve ect

 

five7,
Why do you say the idle screws should be 7 turns out? My shop manual says 3. Are there different specs for different quadrajets?

 

The CC q-jet idle mixture screw threads are a finer pitch than non-CC q-jets. It takes more turns to move the needle out the same amount.

As to differences in cats - monolith is the only thing I know of anyone making anymore (pellets are history). The difference to which you refer is in catalyst function (the actual metals used), not flow path design (which would affect plugging or not plugging). Universal replacements often will state they are 2-way or 3-way, depending upon whether or not you hook A.I.R. up to them.

Worn valve guides will affect oil getting into the cylinder - more slop means easier for oil to get in there, and also makes positive-type seals less effective (and o-ring seals completely ineffective). It really doesn't take that much wear.

 

Didn't know that about the mixture needles. But my qjet is a ccc model and the shop manual is for a ccc carb. I rechecked today, it says to turn the idle mix screws out 3 turns. Why is that?