Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Need help with recipe #1 No Idle

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Cliff Ruggles:
Re-size the lower idle airbleeds, or you will need much larger idle tubes, probably around .039-.040" to get close to recipe #1.

The "recipes" work, and are street, dyno and track tested.  These thing do however, involve EXACT precision.  Unless you duplicate all the sizes at every location, the fuel curve will not end up where it's supposed to.

Also keep in mind that the float height and fuel pressure have an impact on the results as well, as does the size of the float and the diameter of the fuel inlet seat.

Did you get a kit from us and set the float to exactly 1/4"?......Cliff

mrk3cobra:
Cliff if I read your post correctly I will re-drill my new idle tubes to .039 and leave the lower air bleed at .078
and change the float level from 3/8" to 1/4". Does this sound correct.When I checked the fuel pressure it was bouncing between 4-6lbs. thanks,pete

Cliff Ruggles:
You can attempt to compensate for the large lower idle airbleeds with a large idle tube.  I prefer to make them smaller, but a large idle tube and possibly more idle downchannel will help.....Cliff

mrk3cobra:
I tried, the motor still has the same problem as it did in my first post.

Looks like I will throw the Edelbrock carb back on the motor, it idles perfect with the Edelbrock carb.

I give up on the Quadrajet I have torn it down 3 times and it runs the same as it did before I made any changes with the Quadrajet.

Cliff Ruggles:
As we've mentioned many times, carburetor building involves EXACT precision.

The float level is set low, we recomend 1/4".

All of the items in the "recipe" are not within the recomended range.

The results may also be comprimised by other things, throttle plates not fully sealing (interntal vacuum leak), leaking at the primary throttle shaft, etc.

A low fuel level in the bowl, combinated with large idle airbleeds will not delviery the intended results. 

No mention was made if shaft bushings were installed, and or the size of the fuel inlet seat, size/type of float, etc.  All of these items effect the fuel delivery, and are well covered in our book.....Cliff

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