The following excellent write-up was provided by Dan Davis
Rochestor Carburetor used on the 429 CJHistory
Ford used this carburetor due to the increasingly strict Federal emission laws, as they did not have a low emissions carburetor ready for the introduction of the 429CJ. Ford wanted to avoid the costs of fitting an A. I. R. system to 429CJ engines as this was said to run about $75 more per vehicle factoring in parts, assembly and warranty costs (that's about $195 in today's dollars!). Their choice was to buy cleaner running carburetors from a supplier who just happened to be General Motors.
This is a top view of the 429CJ Quadrajet carburetor for automatic trans, non-AC applications. Notice the Ford auto trans kickdown lever (green). Also note the dashpot on the throttle linkage side. It was used to avoid stalling by gently closing the throttle when then driver suddenly released the pedal.
Air-conditioning equipped vehicles used a solenoid in place of the dashpot. Its function was to prevent run-on (a.k.a. "dieseling"), which was found to be a problem due to the increased operating temperatures of AC-equipped vehicles. This solenoid was powered with 12V when the key was in the ON position. It would raise the throttle shaft slightly off the idle screw, thereby controlling the idle speed. Moving the solenoid was the required method of idle speed adjustment. The idle screw was set to ~500 rpm with the trans in neutral. The idea was to allow the throttle plates to close to a point below normal idle speed on shutdown (i.e., solenoid de-energized), choking off air supply thereby preventing dieseling.
To ID a Quadrajet look on the carburetor body on the drivers side behind the secondary throttle lever. You will find a number similar to 7040286. Here is how to decode it:
The 429CJ Q-jet was only produced in 1970-71 as a 49-state part with two numbers (AC or non-AC) each for manual and auto trans. (4 numbers total). They are as follows:
7040285 = Manual trans w/AC; Autolite tag D0OF-F
7040286 = Auto trans w/AC; Autolite tag D0OF-E
7040287 = Manual trans w/o AC; Autolite tag D0OF-A
7040288 = Auto trans w/o AC; Autolite tag D0OF-B
There are two date codes found on the Ford QJ. The first was stamped on the carburetor body by GM and follows the Julian date format, which is the sequential day of the year followed by the last digit of the year. The stamping shown at the right shows a build date of 9/25/1970 (2680).
The second date code can be found on the Autolite tag attached to the carburetor by Ford. This date code is in the format month/year/day. The month code is a letter following the traditional Ford date code format of A-M, skipping I. The tag at the left shows a 12/21/1970 build date (M021). The "A" to the left of the date code signifies first shift.
ON ORIGINAL CARBURETORS, THE TAG DATE WILL MATCH THE STAMPING DATE!The proper date code carburetor for your vehicle would be within 30 days before the assembly date of your engine. However, there is evidence to suggest that these carbs were built in batches and not continuously. Therefore, any date that is within six months prior to your engine assembly date should be acceptable (no ruling from MCA et. al. as of yet). The engine assembly date code is found stamped into a small pad near the water pump. This is generally 30-90 days before the vehicle was assembled.
Note that if the metal tag reads Motorcraft instead of Autolite, then the carburetor is a service replacement. A check of the date codes will reveal a build date of 1972 or later.
Jets & Hangers:
* = not confirmed, but likely
Casting number locations:
Base Casting Number: found at the RH rear corner >
< Cover Casting Number: found underneath (disassembly required), LH front corner
IF ANYONE HAS AN **UNMOLESTED** 4 SPEED CARB, PLEASE CONTACT ME ON email@example.com WITH THE FOLLOWING INFO: Primary Rod Hanger/Power Piston #, Primary Rods #, Primary Jets #, Secondary Rod Hanger Letter, Secondary Rods #, Bowl Cover Casting #, Bowl/Body Casting # and Throttle Plate Casting #. Thanks!