quadra-jet question

morgan in ar · Apr 17, 2014

I've had several of these that flood out when
idiling. I've always just replaced them with a
rebuilt carburetor when this starts happening. What
causes this? Is there something I could fix instead
of replacing the unit? Thanks- Morgan

David G · Apr 17, 2014

It is either float heavy, set to high or leaking needle and seat. They are an easy carburetor to work on. The foam floats had a habit of soaking up gas.

k6zrx · Apr 17, 2014

Could the floats have leak or are they foam and getting heavy?

Something simple to check.

Josh

Bob · Apr 17, 2014

They COMMONLY leak at the pressed-in plugs at the bottom of the metering wells.

Some kits have a pair of cutout foam plugs that solve the problem for a while ('til the gas rots the foam).

They can be epoxied while the carb is apart and cleaned, and (IIRC) there's some specialty shops that have better plugs for them.

<img src = "http://image.highperformancepontiac.com/f/tech/hppp_1107_home_remedy_quadrajet_carburetor/32455048/hppp-1107-02-o-%2Bhome-remedy-quadrajet-carburetor%2Bplugs.jpg">
Article

Dean · Apr 17, 2014

Multiple issues can cause your symptoms.

The coated foam float is prone to become fuel logged over time causing it to float too low, raising the fuel level. If it feels heavy or is old, replace it.

The plugs in the bottom of the float bowl are prone to leak allowing fuel to drip into the intake manifold. A visual inspection will reveal this.

Of course, needle/seat/seat gasket must all be in good condition and float level must be correct.

Dean

Anonymous-0 · Apr 17, 2014

The answer is "HOLLEY"

GregCO · Apr 17, 2014

Bob's pic is great and may very well be the issue. They did have that issue with the plugs leaking. A dose of epoxy will take care of it or you can replace the plugs. Always change floats as they do sink over time. Other than that they are a great carb and very tunable. I know people like Holly, but I personally don't due to the power valves blowing out very easily in cold weather when they cough back through the intake. Holly does make two stage power valves that don't blow out, but at high altitude they don't meter so hot and sometimes won't fully go into main metering. Just my experience.
Also check out the choke stove. A weak or sticking choke stove will let the choke hang up and flood the engine at idle.

Greg

Steve@Advance · Apr 17, 2014

The flooding you're having, is it external flooding, as in gas dripping from the venturas and pooling on top of the carb?

If so, you can probably ease the top off and replace the float, clean the needle and seat, and adjust the float level.

If it has a lot of miles, a rebuild kit will get you a new needle and seat, accelerator pump and gaskets.

If it' internal flooding, as in black smoke on warm engine start up, it could be the galley plugs leaking. I've JB welded them with fair success.

Be sure to replace the paper filter and be sure the spring is there to keep it pushed against the inlet fitting. Check the choke pull off, see if it will hold vacuum. Sounds nasty, but suck on it, put your tongue over the hole and see if it holds vacuum.

Q jets were great carbs! They are simple and very tuneable. Back in the day I had boxes of jets, springs and metering rods. Not as good as fuel injection, but served their purpose well!

JMOR · Apr 17, 2014

(quoted from post at 23:07:09 04/17/14) They COMMONLY leak at the pressed-in plugs at the bottom of the metering wells.

Some kits have a pair of cutout foam plugs that solve the problem for a while ('til the gas rots the foam).

They can be epoxied while the carb is apart and cleaned, and (IIRC) there's some specialty shops that have better plugs for them.

<img src = "http://image.highperformancepontiac.com/f/tech/hppp_1107_home_remedy_quadrajet_carburetor/32455048/hppp-1107-02-o-%2Bhome-remedy-quadrajet-carburetor%2Bplugs.jpg">
Article

have found & used replacement plugs that were machined from aluminum with a grove in them for an O-ring. Those worked well.

Steve@Advance · Apr 17, 2014

Wish I had some of the fine cars, truck and boats set on fire by gas leaking Holleys!

Built a 350 Chevy for a really clean old truck. Had it running perfect. Belonged to a hot rod kid, somebody convinced him to "Put a Holley on it". A year later it was in the police pound, destroyed by underhood fire.

Dean · Apr 17, 2014

I agree.

The Rochester Quadrajet is a great carb, much more sophisticated and economical than the crude Holleys of the day.

The Holley is easier to work on but considerably more expensive to work on.

Dean

morgan in ar · Apr 18, 2014

Thanks for all the help! I have rebuilt several updraft carburetors, and diaphragm type, like on a chainsaw, but never a four barrel.

JDemaris · Apr 18, 2014

Quadrajets were prone to having warped throttle bodies and air-horns that caused internal leakage and flooding at idle speeds. Many tutorials around for proper repair. Old news.

AzPeapicker · Apr 18, 2014

Good Afternoon Sarge

Good to see your back on , missed you & your comments . Don't have your E Mail address .

Mine is [email protected]

John in Az.
g

Hobo,NC · Apr 18, 2014

I always open up the hanger (float pin) a little... When you nail down the air horn it seats it firmly in the bowl...

CenTex Farmall · Apr 19, 2014

Another possibility is fuel dripping from the nozzles at idle. Improper idling caused by air leaks, worn throttle shaft in throttle body and dirty idle circuits and even worn valve guides can end up being compensated by adjusting the idle stop too far open. The resulting air flow is just enough to pull fuel from the mains but it drips out instead of being atomized. You end up overly rich on most cylinders but still running.

rdandersom · Apr 19, 2014

What are you bolting the Q jet to?My son built a stroker V6 in a 84 S10.With crank cam and high compresion pistons it wouldn't take any 4 barrel carb.For some reason it always worked better after we put an adapter on the aftermarket manifold to take the original 2 barrel it left the factory with.Q jet always seemed to run rich at idle then bog out when he punched it.

quadra-jet question

morgan in ar

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