The Mopar 440 engine is a common big block engine of the muscle car era, powering such iconic cars as the GTX, the Charger, the Challenger, the Barracuda and others. The 440 is mostly noted for its high performance profile, combining bottom-end torque with top-end horsepower. The 440 Mopar can be tougher than other big block engines to precisely tune due to a common feature for some models -- the 440 Six Pack. The Six Pack refers to six one-barrel carburetors that feed up to 1,350 CFM into the engine. Tuning each individual carburetor to function in sync can be tricky, and requires patience.
Remove each spark plug and use the spark plug gap tool to ensure that there is an adequate gap for each plug. Replace each spark plug as you work your way around the engine. Loosen the bracket that holds the distributor in place. It is located on the intake manifold. Do not remove the bracket, just loosen the bolt.
Attach the probe of the timing light to the spark plug wire of the Number One cylinder (front left). Attach the other cable to the battery post and start the car. Check the timing by watching the strobe of the timing light flash onto the harmonic dampener. The markings on the dampener will give you the degrees of advance that the engine is running.
Rotate the distributor if the engine timing is too far advanced, or not advanced enough. Continue to use the timing light as you turn the distributor to dial in the proper timing precisely. Though it varies by type, the general timing specifications call for 12 degrees before top dead center.
Turn the metering jet screws on the inside carburetors while the engine is running. Turning to the left lets in more fuel, turning to the right restricts fuel. Try find the proper balance that allows for a clean, even idle. Tuning the metering jet screws will take trial and error to perfect.
Remove the four carburetors on the outside corners of the Six Pack if they require adjustment. Those carburetors do not have adjustable metering, so the base plates will have to be altered to regulate air and fuel flow.
Expand the opening on the base plate with the portable drill if the nonadjustable carburetors are running too rich. If they are too lean, find new base plates that have smaller openings.
Adjust the air-fuel mixture by using the flat head screwdriver to turn the metering screws on the front of the carburetor. There are two screws, as opposed to the Six Pack which has one per carburetor.
Turn each screw clockwise to increase fuel flow and counterclockwise to restrict fuel flow. You will need to adjust one screw in conjunction with the other to achieve the proper balance since one screw adjust the air fuel mixture for the primary butterfly, the other for the secondary butterfly.
Set the idle screw for the proper rate of resting idle. For most 440 set ups, this will be between 800 and 1,000 RPM.
