Competition Carburetor Enclosure Kit

McCulloch introduced the competition carburetor enclosure kit, which was designed for Thunderbird, Corvette and Oldsmobile Edlebrock 3-2 inlet manifolds, in December 1956. This kit consisted of a polished aluminum box to enclose the carburetors, plus all fuel lines for the three carburetors, and the inlet hose and clamps, and was retailed at $125. The air box included throttle and fuel line connections through the base of the air box. The Edlebrock manifold, carburetors and carburetor linkage was not included as a part if the kit, and had to be purchased separately. In order provide a non interference fit of the carburetors to the air box base for Thunderbird installations, the carburetors used had to be truck carburetors. The throttle stop screws and high idle cams of the passenger car carburetors interfere with the air box base plate.

Ford also offered the competition carburetor enclosure kit, in conjunction with the Edlebrock 3-2 manifold, for both Ford and Thunderbird vehicles, although this was as a dealer installed option. This set up, in conjunction with the equivalent 2-4 setups, was one of Fords racing packages available during 1957.

The competition carburetor enclosure was claimed to offer better pressurized air distribution, and a complete lack of fuel leakage due to pressurization of the carburetors. An additional advantage was that modification of the carburetors to make them air tight, was not required.

McCulloch did recommend some modifications to the carburetors, with the most significant being that the air horns of the carburetors were turned down in a lathe to lower them, in order for air flow, and consequently performance, to be improved, and the carburetor jet sizes (as covered in the installation section of the site) had to be increased to compensate for the leaning out of the fuel charge that supercharging generates.

When installing the air boxes and triple carburetor set ups, typical problems encountered were:-

  1. Binding of the Edlebrock linkage due to clearance problems.
  2. The Edlebrock linkage has to be inverted to prevent interference with the air box base. This results in an incorrect leverage direction of the linkage which has to be accommodated for by reversing the throttle arm at the base of the air box.
  3. The heater control valve had to be relocated to allow clearance for the air box.
  4. Oil breather pipework had to be relocated, or re-routed to allow installation of the manifold and air box.
  5. Supercharger relocation was often required, to provide sufficient clearance for the air box.
  6. Fuel vapourisation  in the air box caused hot starting problems. This could be cleared by installing a flapper valve in the air box, or in the connection between the supercharger and air box.

Once installed and operating, the triple carburetor setup in conjunction with the McCulloch supercharger made the host vehicle a very capable performer. Al Heboian took his McCulloch-supercharged T-Bird (Fordomatic, stock bore and stroke), with the competition carburetor enclosure and Edlebrock triple carburetor manifold, up to 101.33 mph from a standing start in the mile, which is a vast improvement on his original best of 82 mph. Harold Stephan of Los Angeles made 103.5 mph in his 55 Corvette at the Long Beach drag strip, using the competition carburetor enclosure and Edlebrock triple carburetor manifold. Another set up was purported to have achieved 146 for the standing mile during tests on the California dry lakes.