Actually this is a very good question with a somewhat complex set of answers.

From the “air cleaner” up they’re 100% compatible! Seriously – that’s the only 100% correct answer. There are a couple considerations.

First part of the “the answer” - Edelbrock used to sell (from time-to-time) Q-Jets that were reconditioned (not new) Rochester carburetors. They built them back to factory original specification and these were really good units in terms of quality and reliability however; they are somewhat rare as the source (original Q-jets) has long since dried up. In the past, they were available direct from Edelbrock, but I do not see them on their web site anymore so they may be out of the “rebuild” business. Tricky part here is the linkages as Edelbrock rebuilt “Chevy-only” Q-jets and if you wanted to use them on a Buick, Olds, Pontiac or Caddie, you needed to swap in the original brackets and kick-down linkages. This situation was exacerbated by the “cash-for-clunkers” program when the government paid people to trash a lot of 1970-1980 cars that were originally equipped with Q-jets. The program required these cars to be disabled and more often than not, they were crushed with the engine intact so the carburetors were destroyed.

Second part of “the answer” - Edelbrock used to market a “Performer Replacement Series Carburetor for Q-Jet” which was an “all new” carburetor intended to replace the original equipment Q-Jet spread-bore carburetors on 1966 -1989 non-computer controlled Chevrolet/GMC V8s. These carburetors look very similar to Q-jets (even gold color) however there are some very subtle differences and the internals are not interchangeable with Rochester manufactured Q-Jets. The Edelbrock replacements are (for the most part) compatible with all OEM linkage and bolt on to the stock intake manifolds. I have used the 1901 and 1902 over the years but they are not easily found anymore. One way to know you have an Edelbrock Q-jet is that they use Torx head screws. There were five distinct models of the Q-Jet replacement (this from an old Edelbrock tech-sheet dated 2002 I’ve for whatever reason kept in my files!!):

1. #1901 (750 CFM) - Recommended for most small-block and big block Chevrolet/GMC V8s, 327 through 454, in both truck and passenger car applications using a remote style choke; 1966 to 1973.

2. #1902 (750 CFM) - Recommended for most small-block and big block Chevrolet/GMC V8s, 350 through 454 in both truck and passenger car applications using a remote style choke; 1974 to 1978.

3. #1903 (795 CFM) - Recommended for most small-block Chevrolet/GMC V8s, 305 through 454., in both truck and passenger car applications using a hot air style choke; 1975 to 1985. (Electric choke conversion – needs a switched 12 volt lead.)

4. #1904 (795 CFM) - Recommended for most small-block Chevrolet/GMC V8s, 305 through 350, in truck applications only using a full electric choke; 1980 to 1989.

5. #1906 (795 CFM) - Recommended for big-block Chevrolet/GMC V8s-454 engines in truck applications only using a full electric choke; 1980 to 1989.

Summit, Jeggs, and others may still sell rebuild kits for the Edelbrock units, but only until their stocks are depleted. I occasionally see one at a swap meet but I’ll not pay more than $25 bucks for an “unknown” carburetor – regardless of the seller’s claims of “recent rebuild” unless it’s an original unit that I know and might be looking out for.

Quick answer – not a lot of interchangeability between “true” Rochester Q-Jets and the Edelbrock units..

The good news is that Summit and others still have rebuilds of the originals for reasonable prices and that's a good way to go if you want a Q-Jet which, in my opinion, was the best factory carb ever used by GM..

Regards,
Glenn