Quadrajet internal spring Questions

[MrSony]

Hello all. I was partaking in one of my favorite hobbies as of late, rebuilding qjets, and as I had to take a break for a few days due to work, I lost track of where these two little springs went, or rather to which part they went too. There is two springs, the top slightly longer and ever so thicker than the bottom. I know one is the PP spring, and the other is for that weird 1 metering rod thing that sits next to the aneroid. This is the first type of these carbs I've dealt with (everything I've rebuilt has been 77-80 so far). btw the carb was on a running and driving car that I drove, it would just stumble and die upon sudden acceleration from a roll or dead stop. Really clean on the inside. Carb is #7045183 if I remember correctly, for a 1975 Olds 350. Anyway, does anyone know which spring is which? Thanks for any input.

 

[pontiacgp]

on that carb they sell a lead plug to plug the hole for the single rod and you block off the fixed jet. I wouldn't use that carb, they used that style of carb for only one year in 75 so that should tell you something

http://www.bdub.net/manuals/Quadrajet_Service_Manual_1981.pdf

 

[MrSony]

on that carb they sell a lead plug to plug the hole for the single rod and you block off the fixed jet. I wouldn't use that carb, they used that style of carb for only one year in 75 so that should tell you something

http://www.bdub.net/manuals/Quadrajet_Service_Manual_1981.pdf

I'm building it for a dude, not really my choice to use it or not. Thanks for the info though.

 

[pontiacgp]

I hope you remember which power piston spring goes with each power piston. The two springs are different with the one in front in the picture being the stronger of the two. The other spring of course is for the high speed idle lever which is on every Quadrajet. What are you going to use to clean the parts?

 

[MrSony]

I hope you remember which power piston spring goes with each power piston. The two springs are different with the one in front in the picture being the stronger of the two. The other spring of course is for the high speed idle lever which is on every Quadrajet. What are you going to use to clean the parts?

Steel parts? Wire or stiff nylon bottle type brush. Other than that brake cleaner or carb cleaner mostly, whatever i happen to have on hand. Never steered me wrong. I would wager that the stronger spring (the short one you said?) would be for the normal power piston and the longer somewhat weaker would be for the single piston.

 

[pontiacgp]

Steel parts? Wire or stiff nylon bottle type brush. Other than that brake cleaner or carb cleaner mostly, whatever i happen to have on hand. Never steered me wrong. I would wager that the stronger spring (the short one you said?) would be for the normal power piston and the longer somewhat weaker would be for the single piston.

did you read the manual in the link I posted? I think you'll lose your wager.

 

[MrSony]

Read it, didn't see anything talking specifically about what spring goes where. But from the sound of it, I have it backwards i spring placement. Short one for the stand alone piston and rod and the long one for the power piston...?

 

[pontiacgp]

This what the manual says, since the single piston lifts before the primary the stronger spring is used with the auxiliary so it will raise with less of a vacuum drop than the primaries needs. It's a common practice to plug the hole for the auxiliary power piston and the jet and just use the primary power piston

"AUXILIARY POWER PISTON
An auxiliary power piston and single metering rod assembly, located in front of the main (primary) power piston, is used for light duty power requirements . On light throttle opening when manifold vacuum drops t o a predetermined point, the spring force under the auxiliary piston overcomes the vacuum pull and raises the piston which lifts the single metering rod out of a fixed metering jet. This provides partial fuel enrichment for light duty engine loads."

NOTICE: The main (rear) and auxiliary (front) power piston springs must NOT b e interchanged . To prevent mixing of power piston springs at time of carburetor disassembly, lightly wrap a piece of masking tape around the auxiliary power piston spring for identification. Then, on reassembly, remove the tape and install the spring in the front location beneath the auxiliary power piston with single metering rod .

 

[MrSony]

This what the manual says, since the single piston lifts before the primary the stronger spring is used with the auxiliary so it will raise with less of a vacuum drop than the primaries needs. It's a common practice to plug the hole for the auxiliary power piston and the jet and just use the primary power piston

"AUXILIARY POWER PISTON
An auxiliary power piston and single metering rod assembly, located in front of the main (primary) power piston, is used for light duty power requirements . On light throttle opening when manifold vacuum drops t o a predetermined point, the spring force under the auxiliary piston overcomes the vacuum pull and raises the piston which lifts the single metering rod out of a fixed metering jet. This provides partial fuel enrichment for light duty engine loads."

NOTICE: The main (rear) and auxiliary (front) power piston springs must NOT b e interchanged . To prevent mixing of power piston springs at time of carburetor disassembly, lightly wrap a piece of masking tape around the auxiliary power piston spring for identification. Then, on reassembly, remove the tape and install the spring in the front location beneath the auxiliary power piston with single metering rod .

Man, I am blind as a bat. Thanks for the clarification.

 

[pontiacgp]

That third rod is a terrible design and there is no need for it. The two main rods can meter the fuel and that is why that third rod was dropped after one year. The third rod just complicated the set up and if I were you I'd talk the owner of the carb into getting rid of the third rod and set it up with the two primary rods. What is the size of the primary rods and the jets?