Q-Jet Mystery....

Okay Bill & Friends...

Take a look at the following page and photos and tell me what the hell is wrong and how I can fix it. Please note, the images are 1248 x 7xx-8xx and there's 6 or 7 of them.

my q-jet page

Problems: at random times, rougher idle and sometimes I have to put it in neutral to keep it running. Doing downhill is a lil different, undescribable, but the elevation change from down to up and it roughens up again. **** mileage imo even if I curb myself from the secondaries for a full tank (boy that's hard too!) I've never gotten over 11mpg.

Primaries function fine while testing with the secondary lockout enabled, and pull fine through 65mph. Since futzing with the secondary side, I've gotten it at a pretty smooth transistion and 0-WOT spins the tires a bit. In gear, she never smokes, no matter where I punch it from. In park or neutral tho, I hit it and she smokes like a cigar. You'll see in the images that I've disconnected the front vac break so I could get into fixing the secondary side, I've left it off as when I hook it up, it bogs again.

Settings: Primary Jets 73, Rods 44B, 8Hg PowerSpring. Secondary B Hanger, BS Rods, 1/2 + 1/8 turn on airvalve spring. Float Height 14/32.

Hope that's enough info.. Thanks Guys!!!

 

Have you checked for vacuum leaks around the base and all around the intake manifold? I had the same problems and found a large leak around the number 1 bolt hole. Soon as I fixed that I was able to smooth out the idle and look at the other problems.

Bill S.

 

QJet blues...

:beer Check the base plate for a sloppy front shaft (common in QJs), creates nasty, variable vacuum leaks that mess with the idle circuit. Cure is thin wall bronze bushings. Hope this helps, Buford

 

Also I noticed that you are feeding the vacuum advance from the base plate on your carb. The vacuum's pretty strong down there, you might try the port just above and to the right to see if that improves your setup (that's where mine used to be). Of course you can try removing it as well and dial a little more initial advance to compensate.

Bill S.

 

Keep lookin guys.. Nobodies seen all the gunk and crap all over the place?

Bill, I tried the vac advance ported, then none, and just recently (cuz my temp gauge hit 220 the otherday) started using the larger full vac port which has helped a bit.. So far, no higher then 200-205..

Throttle Shafts were all good upon inspection and reassembly. I kinda doubt thats the prob, but I'll try some wd40 or brake cleaner tomorrow on the slim chance..

Oh yea, Bill, all screws and bolts were tighened and torqued origianally, then again 4-5 days of usage. They say that once that's done you should be good for years. Beats me.. I'll retorque again tomorrow.. sure, why not.. o No:

Thanks guys for being patient while loading the site too.

 

Hmm... ALl those pictures look very familiar.. : )

It would probably be worth having the throttle shafts bushed. I couldn't do it when I put your carb together, didn't have the tools or bushings.

Also, get your vaccum lines figured out. From the front, the top right goes to vaccum advance, it is ported. You do NOT want to put the vac advance on any other port.

Also, the lower left on the body (yellow cap) should have a 2"ish vac hose to the vaccum break, this will keep your secondarys from opening when you punch it in idle, this may be big reason #1 why it smokes when you floor it at idle. When you are in gear, there is a load on the engine so the engine can actually use the fuel thats being dumped in there.

The vaccum port in the baseplate I believe went to a vaccum tree that would be in the right side water hole (where you currently have the idiot light sensor). It should be plugged on your car.
The top left (blue cap) I am pretty sure would go to the vaccum device on the air cleaner, you should have it capped.

The vaccum port on the back (in the baseplate) I beleive goes to the vaccum "ball" for the a/c system.


Reguarding the secondary side, KNOW THIS, they way the top valves act in N and they way they act when flooring it in 1st is completely different. That is why the vaccum break (lockout) is there. At Idle in N, if you floor it, the power valves should only open a hair and not till your almost redlining the engine. They are supposed to open based on engine load. Thats the what makes these carbs so great.


$.02

Btw Scott, if you decide not to use the vaccum break, I'd gladly take it off your hands, I could sure use a nice one like that.

Dan

 

Scott,

Be careful of 'false readings' when spraying anything on the throttle shafts! When I was at the GS Nats this year, I was talking to the owner of The Quad Shop. He told me even NEW carbs will rise in rpm when sprayed on the bushings. He said a better method is to wiggle the end of the shaft - looking for anything more than 'minimal' play.

You can buy a kit to re-bush your throttle shaft baseplate from the Carb Shop, and others. Or you could just send it out to get done. Should be money well spent!

 

Well guys, I came to an impass last night.. I decieded since it wasn't to shabby outside, to go yard'ing today.

LSS, 3 hours and 2 yards later I came home with a 455-4 aircleaner assembly, and yet another Q-Jet. Both off a '71 Centurion. Tonight I plan on disassembling the carb to see what it's like inside and rebuilt/kit. Then, call up Mr. Osborn and see what he charges to redo one of them. This way, I still have a drivable car. I would also have gotten the distrib that came with it but they wanted to friggen much for it.

The Centurion showed 70k on the dash, was complete engine looked to be cared for and original. Disc brakes were still there as were headlight bezzels, grill (excellent shape) and lots of body panels including some of the interior. Green Int w/Bench.

So, off I go to see what I drug home.

Dan, what vac break you talkin bout? That day you took the one I had, you want the rear one too?

Scott, know anywhere close that has rebush kits? Ontario is a bit far. Would Napa, AutoZone or PAW have it?

Thanks Guys.. One day she'll run good, and cool! (210* not cool)

 

Jet Performance is in your area, that's as close as I know of...

 

Try "The Carb Shop" http://www.thecarbshop.com/ - they're in Costa Mesa. I know...it's different than the "Carb Shop" up in Ontario, Ca. They may have what you're looking for.

I thought all the big shops were in SoCal.!!!:Brow: :Brow:

 

Jet Performance (JetChips) is closer then The Carb Shop, but definatly not as cheap! Jet runs $300+ for what The Carb Shop will do for $250.

Thanks Scott & Adam for the suggestions. And to Scott & Everyone else for all the patient help everyones given me in all the years (yup, years) carbs have been giving me hell.

Once some spendable funds come down pipe, I'll drive to CostaMesa.

Hey John, wanna grab them beers halfway? :Brow:

 

:beer Scott: Send me the base plate and I'll install the bushings for $25 plus return freight. Frank