What carb should I use?

[Sigforty]

I am trying to determine out of 3 quadrajets I have, if any one is a better choice to rebuild.  The numbers on them are as follows:

7040511

7045583

17058212

[429bbf]

wecome to chp. i would take the 17058212 . thats a nice carb and mos are very good castings. fwiw

[Ethan1]

I am trying to determine out of 3 quadrajets I have, if any one is a better choice to rebuild.  The numbers on them are as follows:

7040511

7045583

17058212

Welcome to CHP!

I would also recommend the 17058212.

[Sigforty]

What reasons is that one a better carb?

[Frank400]

   First, those "late" model quadrajets have what they call APT (adjustable part throttle), have a better casting, are less prone to leaking by the bottom plugs, just plain better.  What is going to be your application ?  I strongly recommend buying Cliff's book...that will be one of the best tools you ever bought.  Frank.

[77cruiser]

Do you have a pic of the 17058212?

[Sigforty]

   First, those "late" model quadrajets have what they call APT (adjustable part throttle), have a better casting, are less prone to leaking by the bottom plugs, just plain better.  What is going to be your application ?  I strongly recommend buying Cliff's book...that will be one of the best tools you ever bought.  Frank.

I picked up the book a few months ago and have read through it.

As for the pictures, I do not have any currently.  I got the carb in pieces so I need to see if I even have all of them.

[dlong70elcamino]

I have a 17058213 carb and it does not have APT on this carb.

[77cruiser]

They do but it's the old style in the base plate, under the plug in the front between the idle screws.

[Ethan1]

They do but it's the old style in the base plate, under the plug in the front between the idle screws.

 Yep.

http://www.crankshaftcoalition.com/wiki/How_to_rebuild_a_Rochester_Quadrajet_4MV_carburetor#Baseplate_APT_adjustment_location

 

 

 
 

[dlong70elcamino]

Your right 77 cruiser it does i meant it does not have the one in the bowl.Even the early 70s carbs I have,have the one in the plate. It,s weird that Cliff does not talk about adjusting the one in the plate in his book.

[markedmondson]

Most (maybe all) Q-Jets with base plate APTs are plugged by the factory to prevent field adjustment.  When Cliff repaired by carb, I asked him to install an APT adjustment screw.  Now I can tune part throttle richness with the APT from the front of the base plate with a screwdriver (turning CW raises the seated (high vacuum) position of the primary metering rods).

Interestingly, Cliff at the time commented he gets very few requests for this modification.

[Cliff Ruggles]

The baseplate located APT system was used on a lot of Olds, Chevy and Buick early units.  It is however difficult to get the screw in the baseplate freed up without snapping off the ears on it.

The factory use Loctite and it is very difficult to remove, and the screw is hardened to prevent drilling it out.  We use heat and penetrating oil and can get them out in most cases.  We replace it with an external screw with a spring on it so it holds the adjustment......Cliff