Hype

After fighting with Aircare forever, I borrowed a shops leaned out Qjet and passed with flying colours.

Turns out, I coulda got by without spending hours tinkering with my current one or maybe even without spending $$$ on dual-cats, but hey, live and learn.

Anyhoo, my original Qjet with like 150,000++ miles on it sits back on the car, until I am bothered to replace it. It's gotta be worn, after watching the sniffer graphs I noticed the readings are bouncing everywhere, and seeing as how the only stock thing left on the car besides the original '83 Qjet is the gas pedal, well, what the hell.


So, which carb should I go with? I've been recommended a carterAFB replacement by a couple of guys, but, I would appreciate a decent degree of performance. =)

What I need is a spreadbore, vacuum operated carb either 650cfm or 750cfm I guess. The car is daily driven, and has to (obviously) pass the sniffer every year, but is not required to have a visual inspection.

Thanks guys,

classicgm

I would rebuild it. with that many miles your throttle shaft is bound to be sloppy and that can cause the symptoms you are having. it's reativly easy to rebush at home. you need to find brass tubing at your local hobby shop, have access to a drill press, an 11/32 drill bit and some green locktite.

disassemble the throttle plate (file away the exposed screw thread completely so you dont break them off in the shaft), setup in a drill press, use a 5/16 rod for alignment (I bought brass tubing at the same place I got the 11/32 pictured below), and drill the throttle plate. install the bushing with green locktite and reassemble.

Here's how it looks in my garage..

Damon

Classic- that's some REALLY good info. If I had the tools I'd be re-bushing throttle shafts myself, too. I just haven't had the heart to try it since I don't have a drill press (I suspect most people don't). It's one of those things that I've always farmed out to a local shop- and I've always hated it since I can bring an old worn out carb back from the dead in about 4-6 hours EXCEPT FOR THE DAMNED THROTTLE SHAFT BUSHINGS! Send out to the local shop, wait a day or two and then do my stuff to it.

I assume you do NOT put a bushing in the center section of the TB where the shaft passes through between the throttle bores (you'd need a long drill bit). I've never seen one put in there, but I always wondered if the sloppy fit that usually exists there doesn't accelerate the wear on the new outter bushings. ???

five7kid

iTrader: (14)

Why do you assume your carb is "worn out"? Did you watch the readings with the leaned-out carb, whether they fluctuated like yours did? Most likely they did, but were just lower overall. Your carb may be dirty/mal-adjusted/improperly tuned, rather than beyond hope. Jets/hangers, power piston spring selection, etc., can make a world of difference. It's hard to overcome a warped or cracked air horn, though.

About the shaft bushings: Great info, but I question whether it has anything to do with the symptoms reported. Perhaps. But, to answer the question about wear, the best way to avoid it is to not put the return spring on the bottom of the throttle shaft hooked behind the carb. When you do it that way, both the opening and closing forces have to be reacted against the back of the throttle shaft bushing. But, if you have the spring on the top and hooked in front of the carb, the forces are better balanced as far as the throttle shaft is concerned.

As much of a defender of the q-jet that I am, I question your choice of a potential replacement. Why do you think you need a spread bore? For a daily driver, the spread bore is a good compromise choice between economy and power, admittedly. The AFB isn't spread bore, by the way. Why do you think you need vacuum secondaries? With a manual transmission, any kind of vacuum-operated/controlled secondary carb will be 2nd best to a double pumper.

A Holley or Speed Demon 650 DP would be a great choice for your combination. Unless economy is much, much more important to you than any other consideration.

classicgm

damon, the whole reason to do this is because the q-jet is so sensitive to vacuum leaks so only the outers need bushed. One way to do this without a drill press would to be get an 11/32" reamer with a 5/16" long shank.. feed the shank through the throttle body and, well you get the pic right? Bush both sides and the center has plenty of support so no worries there.

Also, what's your technique for straightening the body and lid? I have a screw down fixture I am working on but it is crude. hope to have pics in a few days...

five7kid, you'll never worry about spring placement again cause the bushing is so stout. look at the close-up drill pic above and you see that the cutting doesnt start until 1/2" or so in the body. Only 1/4" of material supports the shaft in stock form. The bushing can be the full length and is replacable as if you'll ever need to.

Hype

Well, the cheapest way around this would be to grab a junkyard Qjet for $20, get a rebuild kit and give 'er. The Qjet has never let me down, but, if you're going to replace something, why not make it better? And, as a matter of fact, I do have access to a drill-press, well, nothing more than a case of beer will get it done for me anyway.

As for the Qjet being worn-out, when you run your car through here they give you a 60sec printout of the various pollutants as they run your car (at 30mph). The old Qjet shoots through the roof, backs off, shoots up again, etc. The one I borrowed from the shop popped up a bit, then was flat as a billiard table through the 60sec run. And well, its got 20+ years on it and its never been rebuilt. Time for some TLC baby.

The reason I would prefer a spreadbore is just that - its a decent trade-off between economy and power. This thing is a daily driver, and gas ain't cheap when you have 355ci slurping it back through a carb.

As for preferring the vacuum sec. to the double-pumpers, I've heard nothing but complaints with these things - extremely poor mileage, will NEVER pass the sniffer, etc. Is all that worth the extra power? Well, maybe. =)

Actually, I guess I could always have a backup sniffer-prepped Qjet I chuck back on come AirCare time.

It seems to me that a vacuum sec. carb just makes more sense - that is to supply the air/fuel based on engine demand rather than just dumping it in. Doesn't that seem rather inefficient?

Well, now you've got me thinking. As far as power is concerned, what carb is going to be top-dog?

Hey, sell me on something here. =)

five7kid

iTrader: (14)

For area-under-the-curve power, the DP will be TD. Peak power, probably no difference. Frankly, I've never tried to tune a Holley for emissions or gas mileage. But, there are many around these parts that have.

I've got a couple of Edelbrock Performer q-jets. They are supposed to be the cat's meow of spreadbores. I'm quite underwhelmed with the 1901 (old style, divorced choke - had it on the 396), but the 1904 (newer style, electric choke - it's on my horse-trailer towing full-size van) seems to do fine.

RB is a fan of the 4165/4175 Holley spreadbores. I've never seen one run right, but I haven't seen a lot of them.

Soon after clicking the "Submit Reply" button, I'm off to the parts store to see about a kit for my CC q-jet. Emissions test is due, and I don't think it's ever been "quite" right in the 4 years I've had it. It barely made it past the test the last time; when I got home from the testing, I drained the radiator to start the mods.

Hype

Well, in the end, I ended up down at the local parts shop for a Qjet rebuild kit. While shopping for the kit, the local parts junkie offered me his recently rebuilt Qjet at a decent price as he decided to upgrade to one of the new speed demon carbs (surprise, surprise) on his mild'ish 350 powered Malibu. I was a little bit relieved actually, I figured getting into the guts of a Qjet might be a bit of a nightmare. Anyway, just for sh*ts and giggles I slapped it onto my shops sniffer and it read within emissions spec, dinked with the float a little bit, dropped in my beefier secondary hanger/rods and I was off to the races. It seems to pick up at WOT about the same, but better part-throttle reponse, and hopefully better mileage, but we'll see. Thanks for all your suggestions, btw, Aircare sux. =P

Hype

Well, in the end, I ended up down at the local parts shop for a Qjet rebuild kit. While shopping for the kit, the local parts junkie offered me his recently rebuilt Qjet at a decent price as he decided to upgrade to one of the new speed demon carbs (surprise, surprise) on his mild'ish 350 powered Malibu. I was a little bit relieved actually, I figured getting into the guts of a Qjet might be a bit of a nightmare. Anyway, just for sh*ts and giggles I slapped it onto my shops sniffer and it read within emissions spec, dinked with the float a little bit, dropped in my beefier secondary hanger/rods and I was off to the races. It seems to pick up at WOT about the same, but better part-throttle reponse, and hopefully better mileage, but we'll see. Thanks for all your suggestions, btw, Aircare sux. =P

89TurboV6

I don't mean to steal your post Hype but Im having some problems with my q-jet(non-cc) and have no idea where to start. I live in the New Westminster and have to pass aircare come March and I have a feeling my carb will not pass. It runs a little rich at idle when warm, has a slight bog/miss when I leave from a stop and when I go to WOT it bogs untill I lift off a bit then it takes off. I recently gave the car a tune up plugs, pcv, fuel filter, air filter and this helped but the problems mentioned above are still there. I plan to do the cap, rotor, plug wires soon I suspect the plastic hoses may be crap and Im going to replace all them with rubber hoses. What are the 2 things that all the hoses connect into, 1 in the t-stat housing and 1 is in the manifold i think also what is the other thing in the t-stat housing that has a green wire running to it from the top front of the carb?

As you can see Im lost and any help is greatfully appereciated

Edit: Im not looking for a quick fix and I want to keep the q-jet.

rhuarc31

If the airhorn or base are warped I usually fix 'em with my cylinder head resurfacer (big belt sander). If they're way bad, I've got a nice flat peice of 1 inch thick steel that I clamp/bolt 'em to and hit 'em lightly with the torch while applying steady pressure. I haven't had many that badly warped though. There is a place on line that sells a fixture to fix warpage, but I can't remember the address.

Hype

Well, when I bought the car it idled quite high (1,300+RPMs), took forever to warm up, stuttered a bit, etc...

At the time I knew pretty much zip about cars, but I did figure out that those plastic hoses you mentioned were to blame. They were decayed to the point where I didn't even know where to begin, and of course was the source of several sick vacuum leaks.

Soooo, what I did was just junk all that ****e, grabbed an edelbrock nonEGR manifold, and just plugged up the ports on the carb. Apparently EGR brings down your NOx readings, but, I blew 0.00 on the NOx test, so, there goes that theory. There's no visual of course, but the sniffer is very tight. And logically, thats the bottom line.

Your car HAS to be running immaculate to pass B.C. Aircare, we like to have **** competitions with California to see who can be more rententive, apparently. I am running a brand new 350ci with a compXE262, and I had to run a very de-tuned carb to pass. In retrospect, I wouldn't have added any parts to the car that weren't either factory or carried a 50state CARB #.

Just some heads-up for ya.

Damon

I don't try to fix badly warped parts. If it's not flat enough to hold a gasket it goes in the trash. I've found that to be actually quite rare, though. The airhorn assy. is a pretty flexible piece and will generally seal up when the screws are tightened down even if the parts look pretty far from true. I swear it will bend to fit almost every time. This used to freak me out, but it doesn't any more. As you can tell, I don't generally do "concourse" or "numbers matching" restorations- can't just chuck an original numbers-matching carb in the trash and expect to find another one the next day. I build low-buck high-performance functional stuff, no frills, but everything works like it should.