How to Tune a 400 Chrysler Engine

Chrysler introduced the 400 cubic-inch, big-block engine in 1972. This B-series of motors was developed as part of a slimmer lineup of powerhouses to reduce both complexity in design and eradicate issues caused in the older vehicles. With advertised horsepower varying from 190 @ 3,600 rpm to 195 @ 3,600 rpm over the years, this output was less than that of the more popular B-series engine, the 360 E58. As this motor approaches its four decade anniversary, keeping the 400 properly tuned and maintained is more important than ever.

Things You'll Need

• 4-Barrel Carburetor
• Fuel Pump
• Spark Plugs
• Spark Plug Wires and Wire Puller
• Wrench Set

Instructions

Carburetor Replacement

1. Remove air cleaner from its location on top of the Chrysler 400 engine. Unhook all fuel lines and hoses connected to the old carburetor. Notate each line and hose function with tags to minimize confusion when installing new carburetor.

2. Use the necessary wrench to unbolt the carburetor from the engine. Keep all hardware holding the old carburetor in place for later use. Clean off any dirt or build up on the engine where the old carburetor was positioned.

3. Align new carburetor with mounting surface of the Chrysler 400.

4. Hand-screw bolts at each position of carburetor before tightening. Tighten bolts at each location a bit at a time to ensure even tightening and no warping effect to mounting surface. Tighten completely.

5. Attach air cleaner back into its original place. Start the 400 engine and listen for any leaks that may occur in the newly-installed carburetor. Remove and tighten accordingly if any interference is audibly presented.

Fuel Pump

1. Drain the gasoline from the fuel tank. Unscrew the bolts in the fuel tank mounting hardware and slowly remove the vehicle's fuel tank to access the pump.

2. Disconnect the fuel leads to the fuel pump and set aside in a manner for appropriate tagging later. Use stickers to identify each lead if needed.

3. Turn fuel pump bolts counter-clockwise until completely loosened and remove fuel pump.

4. Attach the fuel line leads to the corresponding outlets on the new fuel pump. Lift the new fuel pump into place and bolt in to secure position. Turn clockwise to tighten.

5. Mount the fuel tank back to its original position with the provided hardware. Add gasoline and test the engine's response to the new fuel pump for accuracy.

Spark Plugs and Wires

1. Pull the boot of the each spark plug wire from its respective spark plug. Perform spark plug and wire replacement individually to avoid confusion when installing and reconnecting.

2. Inspect each spark plug and wire set for signs of corrosion, overheating, wetness, or any other physical damage. Replacing spark plugs and wires is cheap and much more effective than trying to remove and repair.

3. Remove any spark plugs and wires that are damaged. Turn plugs counter-clockwise with wrench to remove.

4. Hand-screw new spark plugs by hand. Turn clockwise.

5. Reattach new or used wires by pulling boot completely over the intended spark plug. Repeat steps for each spark plug and wire combination.

Tips & Warnings

• Disconnect the engine's battery at the negative connection before performing engine maintenance

• Wear gloves at all times to avoid any injury during maintenance

• Consult local automotive parts stores for best engine part replacements

References

• Allpar: Mopar B Engine Specifications
• The Poorman's Off Chassis Restoration: Chrysler Imperial Tune Up Specifications