Quadrajet dripping fuel out of the primary throttle shaft

[Buzzard77]

Greetings!

I've had my '67 Camaro 325hp 396 blueprinted and dropped the compression a half point to 9.5 to 1, upgraded the valve train and added a Comp Cams 270HR Magnum roller cam.  The car has a factory Turbo 400 and a 12 bolt with a 3.73 gear set. I've got a TCI Breakaway converter waiting to go in when the car gets done at the body shop and is reassembled.

Here's the problem. I purchased a used Quadrajet 4MV #7027200 since the stock carb was missing. When the motor shop put the motor on the dyno, the moment the electric fuel pump was switched on (the motor NOT running) they said the carb began dripping fuel externally from the primary throttle shaft. I asked if the fuel was spurting from the vent tube and they said "No. It appeared that the carb was leaking internally and also traveling to the outside via the throttle shaft. "

What might the problem be? How can the fuel be leaking internally if the needle valve is controlling the fuel at the proper float level? Is there a fuel passage leaking somewhere? I was not present when this occurred and they substituted one of their carbs to perform the initial running of the motor.

I'll probably be sending the carb to you, but I'm worried that something may be beyond repair. I want to keep the motor correct appearing externally with the correct part # and dated carb. What do you think the problem may be?

Thanks for your time,
Buzz

[429bbf]

buzz do you feel comfortable taking the carb apart? i would first see if its got the proper gaskets. then i would fill it with fuel on the bench and see what happens. there electric pump could have made to much pressure who know theres a thousand things that could be wrong . remember simple and easy is the way to start. fwiw.

[Buzzard77]

buzz do you feel comfortable taking the carb apart? i would first see if its got the proper gaskets. then i would fill it with fuel on the bench and see what happens. there electric pump could have made to much pressure who know theres a thousand things that could be wrong . remember simple and easy is the way to start. fwiw.

I suppose I could. I'd given thought of doin' just what you suggested. And you're quite right about the "simple and easy" tip. Don't make things harder than they are. A favorite saying of mine is "Just because it's NEW, doesn't mean it's GOOD!"

Can anyone tell me how much fuel a Qjet fuel bowl holds? I could then pre-measure the fuel and squirt it into the carb down the vent tube. Just to ensure that I'm not over filling the carb.

[429bbf]

i can't answer the volume question and nor can most people . we don't know what float is in it or any other things that some one has done. i would take the throttle body off first. thats the easiest. and check the gasket and the base and fuel bowl. if that all looks good then i would pull the top and fill it with fuel on the bench.at the same time you can kind of look it over and see what was done to it.i don't buy any carbs that have rebuilt stickers on them. and i have very few problems with an overhaul.the problems I've had is when i use over the counter parts . one lasted 20 minutes and the piston swelled and fell off the acc.pump.hth. ps most throttle shafts when there loose  suck a little vacuum when there running and cause a bad idle .i replace all mine with bushing regardless how tight they feel.

[Cliff Ruggles]

Could be leaking at one or more of the bottom plugs and migrating out the shaft, but most likely just flooding.

I see this a lot, especially with the early carburetors that used the old plunger fuel valve and have been upgraded to the replacement N/S assembly.  Most likely leaking at the plug for the bypass, or under the seat at the gasket.....Cliff