Remanufactured Rotchestor Tech Info

M4MC type (hot air choke), M4MC Quadrajets have an integral choke and a different airhorn design; also, the throttle shafts are longer than in 4MV carbs. Starting in 1968 carb numbers were stamped on the driver's side, near the back.

Identification.          There are three basic types of QJet: the original 4M (starting in 1965), M4M (1975 onward) and E4M (from 1979). All QJets had automatic chokes, of which there are two basic types - integral (choke coil on the carb) and remote (choke coil on the manifold). 4MV carbs have the choke coil on the manifold and 4MC carbs have it on the side of the carb in a housing. An M4MC carb has a choke coil on the carb; and M4ME carb has the same type fo choke coil, but with an electric heater element in the choke coil.

Choke parts, primary metering rods and throttle shafts are not interchangeable between 4M and M4M carbs.

Unlike most other 4-barrel carburetors, the Rochester Quadrajet 4-barrel carburetor allows the throttle plates to be opened wider, making the carburetor more efficient. The Rochester Quadrajet 4-barrel carburetor also creates a better throttle response time and has a centrally-located float that gives excellent fuel control. Adjusting a Rochester Quadrajet 4-barrel carburetor is fairly simple when following these tips.

Tools for Adjusting a Rochester Quadrajet 4-Barrel Carburetor.         The tools required for adjusting a Rochester Quadrajet 4-barrel carburetor include a Philips screwdriver, needle-nose pliers, and carburetor cleaner. Cleaning the carburetor prevents soot or buildup from affecting the carburetor's function. Be sure to wear gloves to protect your hands while adjusting the carburetor. Having the right tools in place help you optimize the performance of a Rochester Quadrajet carburetor.

Adjust the Idle Mixture Screws.      Begin on the driver's side and unscrew the idle mixture screws using a Philips or straight screwdriver in the front of the carburetor until the RPM starts to drop. Turn the screw out until it reaches the maximum RMP and is no longer rising. Repeat this process on the passenger side. Be sure that during this process, the screws are turned out only enough to reach the maximum RPM.

Remove the Air Cleaner.        Remove the air cleaner to inspect the top of the carburetor. If fuel is dripping, remove and clean the float and needle. Remove the top screw on the carburetor and turn the nut out. After you clean the float and needle, place the pieces back into the carburetor, taking care to adjust the float so that it contacts the needle. A carburetor adjusting tool or pliers are helpful for this step.

Adjust the Air Valve.           Loosen the spring tension slightly on the air valve until it begins to bog down a bit. Then, bring it back up until the bog disappears. Do not open the air valve at a full 90-degree angle because it can inhibit fuel flow. Opening the valve beyond a 90-degree angle can cause a lean spot, which affects how well fuel is transported from the tubes to the carburetor. This can cause serious damage and block the flap openings.

How to Buy Tools to Adjust a Rochester Quadrajet 4-Barrel Carburetor.         When setting out to adjust a Rochester Quadrajet 4-barrel carburetor, you can peruse a wide array of listings or simply contact us . If using the internet use the convenient search bar, available on every page, which allows you to type in simple phrases, such as "tools for adjusting a Rochester Quadrajet 4-barrel carburetor." When the results populate, you can click on each item for more details. You can even narrow your search by clicking on one of the categories located on the left-hand side of the page. Be sure to view any available photos to ensure the quality condition of a product. Moreover, review any reviews and ratings on the seller before entering into a transaction.