For a bog on the secondaries being engaged, I would first check the air valve diaphram to serif its dead, just suck on it, if its junk it won't pull in and stay.(they also have different dia. Orifices which regulates how fast they release when you stand on the gas. I have found .013-.015 orifice to be best all around whether a cruiser or a bruiser. Next is the air valve spring adjustment, I go about 1/16-1/8 turn past just enough to shut the door, and then tune it with the diapbram orifice size. There are two outer tubes in the air horn that go into side resevoirs, next to the main float bowl/chamber. They are activated by manifold vaccum when you go heavy on the pedal, and give a squirt of fuel while the doors are opening and getting the.main secondary fuel circuit rolling, something like a secondary pump. I have taken the air horn off many a Qjet to find those tubes have fallen out and are laying in the resevoir negating any fuel shot from happening. Make sure you take the rear metering rods & hanger off before trying to put the air horn back on. Otherwise you'll be there for hours a bend the crap out of the rods.
Pull over enrichment tubes and yes I have seen them fall out, you can see the fuel spray while winging the engine (if it backfires, who needs eyebrows but wear safety glasses) You could tell a real QJ guy, we never pulled the rods and hanger, just needed the proper angle on the dangle, doing it 5 times a day helped developed this skill!!!
Well DANG! 36 years of Q-jet'n and I'm not official yet because I prefer removing the rear metering rods/hanger while taking the air horn on and off (especially the rear carb on my tunnel rammed small block chevy that resides under the dash in our '56 Gasser. The first one I ever built when I was 13 years old was from one of my dads work vans. After struggling to get the air horn on (with the rods/hanger attached), and tweaking the tips, my dad says, why don't you just take them off, and put them back on after you have the air horn on. It worked for me.., so 36 years later, still doing it the same way.
I guess some of us had more finesse!!! Remember just about every QJ from 73-86 had the top off under warranty. A dealership tech getting .3 to do this had to become adroit at that maneuver to save the 90 secs per top to make money. Of course if you couldn't do it, no shame in doing it the slow way it just wasn't a problem for us dealer guys...
Great carbs when set up well. The early '80's units often had driveability issues, they would stumble because they were set up very lean for emissions reasons. They had hardened caps over the primary mixture screws that made them impossible to adjust. You had to cut into the base flange below the caps then punch the caps out. Then the mixture screws had a double D shaped head that required a special tool to turn them. The floats were set very low as well. Once the float level was raised and the idle mixture richened, it took a lot less throttle opening to get the car moving, and the off- idle stumble would disappear.
We used to see lots of Q-Jets (and Carter AFB's) with bent rod tips. Back in the day, when rods were semi-readily available (generally special order); this was merely an expensive nuisance (rods have never been cheap). Today, virtually all rods are obsolete, and one must either pay a machine shop with a very expensive lathe to fabricate, or find the same rod on Ebay. Regardless of the skill of the technician, the extra few seconds necessary to install the rods AFTER the airhorn is installed is probably not going to hurt anyone. Think of it as an insurance policy. Whether Carter or Rochester, carburetors that have rods suspended from the top ALWAYS had the rods installed after the top was installed in my shop. And we DO have the lathe that can fabricate the rods, but it takes a lot longer. My opinion, others will differ. Jon.
Hey that was at 32, at 62 you bet the hanger comes off!!! If I can find my glasses to see that damn lil screw!
How many Q-jets have you guys gone through that the secondary lockout link had never been disengaged by the choke, and the customer had never enjoyed the secondaries? I just threw that piece of crap in the trash. I always loved those rebuilds, cause the customer would think you gave them a new engine when they stomped on it and got to experience all 4 barrels for the first time.
When my dad passed away, he added several hundred carb cores (mostly) Q-jets my own inventory. If you guys are looking for a specific casting # PM me.
I had an Estate Wagon with about 75K come in for lack of power. The Power piston was stuck down and it had no mechanical or vacuum advance. The sprag clutch in the converter had flipped so it had no torque multiplication (like 750 stall) and the governor was hung so it started in second gear. I watched the lady pick it up and she spun that right rear about 20 feet leaving the cashier! Guess she was used to flat-footing it to stay up with diesel chevettes...
I did a Q-jet rebuild once on a '69 Caprice wagon with a 300HP/350 (7029202) carb I believe. She brought it back 2 weeks later, smoking, top cover in oil mist and leaking oil. She said I ruined her engine with my carb rebuild. Turns out her mechanically aspiring teenaged son had decided to change the oil for her, only he thought you were supposed to fill the engine with oil up to the fill hole in the valve cover. He had given up on that after he put about 16 qts. in it.
I think anyone who works for the general public has heard the "What did you do to my brake lights while you were cleaning my carb?" deal.
Amen to that. I did lots of rebuilds at home when I was younger for added income. I got stiffed or blamed for some other mechanical ailment 1 of every 10-20 times.
I did a Q-jet on a 67 El Camino 275HP/327 once. The engine had dead hole with a flat cam lobe. I told the guy the carb rebuild wouldn't make much difference if any. He said it was ok as he was planning an engine rebuild soon. He wanted to test drive it first, said it ran worse and he wasn't gonna pay me. Told me I didn't have a legit business (my home garage), that he belonged to the local rotary club, and that if I tried to sue him, he would turn me into the city inspectors
I always figured that if I got rid of a deadbeat/a**hole customer for the price of a minor job, it was money well spent.
Good way to look at it. I know for a fact that this particular guy stiffed a bunch of mechanics this way, an ended up with Parkinson's disease in his early fifties.
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