Quadrajet bogs or hesitates if accelerate heavier than normal

[Brboles]

Quadrajet bogs or hesitates if I get on the gas when accelerating while changing gears if I get on the gas more than normal. If I let off the gas and get on it right good it will hesitate or bog down. What should I look for to fix this problem?

[Brboles]

The truck also does not have this problem when the choke is on and has better power also. Is my secondaries opening too quick?

[429bbf]

little more info would be fantastic , just built ,who rebuilt it , carb no. engine size, has it always been on this vehicle.the more info the more folks can help you . it sounds like its to lean for what you have it installed on .todays gas dent have the bang. we have 91 with no ethanol at all the pumps in northern wyoming so we don't have a gas problem like a lot of folks have. fwiw

[Brboles]

It's a 1986 Chevrolet c20 with a 350, carb is a quadrajet 4 barrel 17085003, rebuilt by a local mechanic here in NC about 6-8 months back. This is the same carb that's been on it since I have owned it for 3 years I'm not sure if it's factory or not I would think it may be. The truck has better power and feels like it. Oils pull a house down when the choke is on and it doesn't have any hesitation then. When the choke comes off the power is not as strong and it has the hesitation going through gears and especially when you are trying to accelerate quickly. I have the vacuum advance line hooked up to the port on the drivers side of the quadrajet the way I interpret the factory drawing. I have tried to advance the timing slightly but no luck. I have the idle set to the factory spec of 800 rpm. Any and all help is greatly appreciated and I will be glad to answer any questions to come to a solution. Thank you.

[Dogmeister]

It sounds like to need to check the spring tension on the seconadries air flaps. If it's too lose it can bog. Start with 1/2 turn after the spring contacts the pin. Increase to 3/4 - 1 turn if necessary.

[Brboles]

Would the secondary spring tension cause it to lose power when the choke is off?

[77cruiser]

Pull the air cleaner & check if the secondary rods are lifting when you manually open the air valve.
Is the timing good? Does the mechanical advance work? Weights could be stuck in the distributor.

[Brboles]

I have tried to advance the timing and no change. I do believe the mechanical advance is working. When I set the idle mixture after the carb had been rebuilt, I set it for the highest vacuum. Is this correct or do I have the mixture too lean causing a hesitation or bog?

[Brboles]

Could power piston adjustment be the problem? If so how can I adjust?

[77cruiser]

If the power piston is stuck down it could cause it. You can check it by putting a small screwdriver down the vent on top, you should be able to push it down with the engine off. Be gentle though!!

[Brboles]

Can you see the power piston with this carb without taking the top off?

[Cliff Ruggles]

It sounds like you have multiple issues, lean on the primary side and a lean "bog" when trying to accelerate quickly.

Goes back to the "rebuild", if it was done correctly with good parts and correct settings it wouldn't be doing all that.

So, back to basics.  Did you use one of our kits?  Was the secondary cam/spring replaced during the rebuild (these parts come in our rebuild kits).

Verify that the power piston hanger arms weren't bent (95 percent we get in here for rebuilding are).

Do you have access to the APT screw so you can richen it up some w/o removing the top?

Is the choke pull-off releasing quickly and smooth to help prevent stumble/hesitation/bog going quickly onto the secondaries?  This is a BIG problem we see and most of the time the link from the pull-off up to the secondary airflap shaft is not adjusted correctly which makes secondary tuning with the spring HOPELESS.......Cliff

[Brboles]

I don't believe my carb has the apt screw accessable. Is there a way I can access it without taking it apart?

[Brboles]

It has the factory plug in it

[Cliff Ruggles]

Best move at this point is to remove the airhorn, drive out the plug and tap it for a 3/8"-16 set screw to provide easy access to the APT screw.

Check the power piston hanger arms while you are in there, about a 95 percent chance they are bent.  So make sure the arms are level and EXACTLY even when you put it back together.

Most likely you will also need a new power piston retainer so it will stay down during assembly.  All of our kits come with one.....Cliff