2 x 4 Set Up: A Brief History
In 1962 Ford decided that their 3x2 setup and 406ci engine needed to be more. The horsepower wars were raging between the big three automakers. In late 62 Ford/Holley designed and released the List 2652 C2AE-9510-CB for their new 427ci engine. These 2 carburetors were 550cfm each. They had external bowl vents on the primary bowl and a new vacuum secondary lid so the two unit could be connected. These carbs are very rare and were only produced at the very end of 1962. It is possible only one batch was ever cast. Both carbs used a choke flap and exhaust heated autochoke. I believe the first 2x4 intake manifold used was C3AE-9425-H (The first three pictures are of the 2652 set)
Early 1963 and an upgraded version of the 2652 carbs were released. The only difference I see is the metering plate. The 2652-1 C3AE-9510-C was born. The earliest ones I have seen were in January 1963. These were also 550cfm each and both carbs had an autochoke. These carbs used the C3AE-9425-H and C3AE-9425-J low rise intakes. (The next three pictures are of the 2652-1 carbs) These carbs were the only ones used from Jan-July 1963 on all 427 R code cars. There was no clear end that I am aware of to Ford using these. I have seen them dated fall of 63, and some original owners claim to have had these carbs even on early 1964 model cars.
The next pictures show an upgraded carburetor set that first made it appearance.
List 2804 C3AF-9510-BK and List 2805 C3AF-9510-BJ were both 600cfm. Due to having larger throttle plates and bore, the intake holes had to be larger at 1 9/16, so these carbs first came on a hand modified intake C3AE-9425-K. The earliest set of production line BK/BJ carbs I have restored were dated late July 1963. I have had the honor of restoring factory prototype version of these, but to my understanding there are only a few sets of those in existence. I was happy that the set I had went to Mickey Thompson’s old factory lightweight car owned by Mr Ciccote, seemed a great home for them.
The BK/BJ setup had some upgraded features. First it addressed the troublesome dual choke setup by doing away with it. Now there was the BK as a primary carb with full autochoke and the BJ which was not drilled for choke vacuum not for the choke rod or shaft. These carbs retained the primary external bowl vent, but they also added an external vent for the secondaries. The BK/BJ setup was used from July63 and all through 64 on R code 427 Galaxies. Later it saw usage on a few 65 models with the C5AE-9425-K intake. Later still it was used on 428ci Shelby GT500 medium riser intakes. I have seen original BK/BJ dated as late as 1972, presumably over the counter replacement parts.
This information provided by me Drew/AirFuelSpark is based solely on my observations and what I have gleaned over the years. It should be understood that it is just that. If anyone has more solid information to add to the knowledge base, I fully welcome it.