Dripping booster

[406 Q-ship]

OK I have been working on Q-jets for quite a few years and have never run into this issue, now I got two of the Edelbrock 1902 Q-jets dripping fuel from one or both booster.  I have checked the float level multiply times, changed the float, needle, and seat.  Then tried to keep lowering the float level till it stopped dripping the fuel, it never completely stopped at least until the level was so low that the truck ran like crap. 

Early on in this problem I checked the airhorn to see if it has been worpped, I got another one even though the original one was good.......still the same issue.  There has been short windows of time when it would stop dripping and I could get the truck tuned in, but like the cat, it would come back.  I tried both of these carbs on two different trucks, a 74 C10 SWB and a 67 C10 SWB both with 350/350th.  Got any ideas?

[Cliff Ruggles]

Need more info?  What are the engine specs, 350cid 350hp engines or something else?.....Cliff

[406 Q-ship]

Both engines these carburators were on are bone stock low compression 350, one a goodwrench and the other a take out 350 from a mid 1970's passenger car (well at least by how it is equiped that is what appears to be).  Neither one of them have anything other than a stock cam and parts store replacement fuel pump, the goodwrench has a 2101 performer.

One of the Q-jets will be going on a 350 that I just rebuilt (it is the goodwrench, heads cracked) the has a very mild Comp cam (12-231-2) and now will be 9.2 for compression.  I will need to break in the cam in the next week and I don't want to do that with the carb raw fuel dripping in it.

Thanks for the help Cliff. 

[Cliff Ruggles]

Lean at idle will cause nozzle drip.  Do you have control of the A/F at idle with the mixture screws?....Cliff

[406 Q-ship]

There is very little responce from the mixture screws, in or out and that is why I tried the flaot level first.  I used the GM recomendation of the starting point for the idle mixture screws of 2 1/2 out from lightly sealted (that is from memory).

[Cliff Ruggles]

The float level needs to be at the stock height.  Lowering the float will not cure the problem, and may not have the fuel level high enough in the bowl to keep the accl pump well full.

Might want to back out the mixture screws to at least 3.5-4.5 turns, depending on the size of the holes under them....Cliff

[12drag]

I'm having a similar booster problem.
Booster leaks fuel after running the engine.  Engine not running, booster will empty the bowl.
NO change after rebuild.  Replaced "Hygrade"stock rebuild components including float.
Carb seems to be more of a "hot soak" problem; boosters will drip fuel after the car has been turned off hot.  When a restarted is attempted, the booster will continue running fuel into the bowl until empty.  Engine NOT running.
I removed the bowl vent and had the airhorn off several times looking for a problem, without success.
The only thing I could attribute this booster problem to is fuel siphoning through the primary needle and jet.
Any ideas?
1967 carburetor stock 396/350hp.

[Cliff Ruggles]

I had one 1967 carburetor in here a few months ago that would flood as long as there was fuel pressure to the bowl, but have never seen a main bowl syphon fuel thru a booster and continue after shutdown and empty the bowl.

The one we had in here had a leak on the pressure side at the bypass plug.....Cliff

[12drag]

Cliff, I don't follow the term bypass plug.  Are you referring to the external plug in the fuel filter housing?
Fuel pressure runs 5psi and drops off after engine is off.  Dwell & timing are correct.  Maintains steady 12" vacuum (no leaks) at idle.  I don't believe this condition has anything to do with engine setup.  I went as far as to lower (less fuel in the bowl) the float (8.7grams) until I got a drive-ability problem.  It ran far less fuel over the boosters when engine was off but it still bleed over.  I would appreciate any help with this odd ball problem.
Thank you,
Jim

[Cliff Ruggles]

The bypass plug is needed and used on the early 65-66 and some 67 castings.  Those carburetors originally had the plunger type fuel inlet valve, and when rebuilding them the superceded parts are used to convert them to a needle/seat arrangement.   The bypass hole is plugged during this procedure, and a frequent leak point on the pressure side of the system....Cliff

[12drag]

The carb. already had the updated needle and seat, but that doesn't mean this bypass plug was install by the previous re-builder.  Am I looking under the seat for this bypass?  If so, can you sell me something to plug this by-pass?

[Roger3]

12Drag,

I am having similar problem (dripping boosters) with my 1967 quadrajet on camaro 350 engine.

It was leaking with original ball bearing needle valve. I disassembled carb, soaked it in carb cleaner, put it back together using Napa carb kit. Napa kit had needle and seat assembly and brass plug with o-ring to block passage next to needle and seat. Here's part of the Napa instruction sheet.



With new Napa needle and seat, gas was pouring out top of carb. I put old ball bearing needle valve back in. It functions, but gas drips out of boosters while it running and continues dripping after engine is turned odd.

What brand kit did you use? What was in the passage next to your needle and seat?

Thanks

roger

[Cliff Ruggles]

I see this a lot with those units.  Most likely leaking at the bypass plug.  The "O" ring they used doesn't hold up well in this new fuel.....Cliff