Q-Jet Bog

[Mark --]

Got my pulling truck back together - advanced the cam 6 degrees and put a rebuilt Q-Jet on it that was off a 454 truck. It has a little electric plug on the passangerside front. Rebuilder said it was an enrichment circuit.

So If I put a ground and a hot wire to it - I get more fuel?

I disconnected the linkage which limits the upper enrichment flaps from the choke.

When I stomp on it I got this big bog the watch out - Can I do something about that??

Thanks for any help - I'm limited to a single feed carb - so I thought the QJet would be the best way to go.

[cadillac512]

Hi Mark
The long wire linkage from the choke pull-off diaphragm to the rear air flaps must be connected,and so must be the choke pull-off vacuum hose.Without them the air flaps open too quickly and a bog results. If you still get a bog,there are two screws near the linkage connection of the flaps.Hold the slotted one in place with a small screwdriver while loosening the small allen screw that points straight down.Then rotate the slotted screw clockwise a quarter turn or less to tighten up the spring on the flaps a bit and give it a try. Experiment with the spring tension a bit and you will get it dialed in.
Terry

[Mark --]

OOPS -- I cut it in half

I'll have to see about scrounging one up....... :lol:

[pageboy]

I'm going to venture that you will be better off with a non-electronic pre-emission Q-jet.

Another thing that can cause Q-jet bogging is the brass tubes that belong hanging in the air horn fall down into the main body. If one has fallen down, it will bog and nothing will cure it. If your rebuilder is any good he should have caught this one. One more thing is that the secondary throttle linkage is almost always out of adjustment on a used Q-jet. Slowly open the throttle to wide open and watch how the secondaries open up. They should have an initial slower opening rate before stepping into a high opening rate, and then should be fully open at WOT. Usually the linkage is so far out of adjustment that the initial slow rate is completely gone and they don't fully open up. When this happens you have a very difficult time getting rid of a bog. Depending on how good your rebuilder is, he may or may not catch this one. Let me know if you need some elaboration on secondary throttle linkage adjustment.

[dave_brode]

Mark,

No offense meant for sure, but: if you aren't carb savvy, a Holley just might be easier for you to dial in. For your needs, throttle response and the ability of the engine to pull in the middle is a must. I really like Q-Jets, but they can be a bugger to tune, esp to get the AFR correct while the air doors are opening.

If you have a stock intake, I might be inclined to try an 800 cfm Holley Spreadbore. It'd bolt to a Q-J intake. They came in both vac and mech secondaries. A vac secondary would be my choice, unless you have a 3000+ stall convertor. They are abundant on e-bay.

If you wish to use a Q-J, I'm with whoever said: get an older version.
Be prepaired the spend mucho time tweaking.
Dave


Dave