Built for the late-model Ford Mustang, the 4180 Holley carburetor is a 600-CFM, four-barrel carburetor with a single pump and dual center-hung floats. Considered to be a mid-size carburetor for street applications, the 4180 has two bowls, but only carries one power valve, positioned at the back of the primary metering block. This carburetor is popular among racing enthusiasts because of its secondary bowl and metering assembly, which allows for the addition of a secondary fuel pump and power valve for increased performance. The rebuild process is identical to that for all late-model Holley carbs.
Orient the carb so the throttle body faces away from you. This places the carb as it would rest on the engine, and allows you to identify the primary and secondary bowl assemblies. Remove the primary bowl by unscrewing its four bolts with a socket wrench. Repeat this process on the secondary bowl.
Unscrew the primary metering block and remove its main jets and power valve from the front and back side, respectively. Spray the bowl and metering block, along with all components, with carb cleaner. Note that you will not need to pull the secondary metering block off, as it does not contain a power valve.
Remove the base plate and peel the base gasket off the bottom of the main body. Match the gasket with the correct one from the set and discard it.
Rinse all parts of the carb body and interior components with carb cleaner, removing all gasket remnants and fuel residue.
Insert the base plate and gasket, screwing the base plate screw tight. Install the new power valve on the back of the primary metering block and secure the block to the main body. Screw in both main jets on the primary and secondary blocks with a screwdriver.
Slide the bowls over each metering block, with gaskets pressed between, and tighten the bowl bolts to 60 inch-pounds of torque with a torque wrench.
Remove the cover off the accelerator pump and inspect the pump diaphragm. You may opt to keep the old one if it is not visibly damaged or plugged with fuel deposits, but replacing it is the best practice. Screw the cover screws back on to complete the rebuild.
