How to check and replace spark plugs on a 1970 Plymouth Hemi 'Cuda?

Checking and replacing the spark plugs on a 1970 Plymouth Hemi 'Cuda is a crucial maintenance task that can ensure your engine runs smoothly and efficiently. If your vehicle experiences misfiring, hard starts, or decreased fuel economy, the spark plugs might be the culprit. Here is how to solve this issue.

Step 1: Gather Necessary Tools and Supplies

Before beginning, make sure you have all the necessary tools and supplies. You will need a ratchet with an extension, a spark plug socket, a gapping tool, a torque wrench, and the new spark plugs. The spark plug socket typically has a rubber insert to grip the plug securely.

Step 2: Locate the Spark Plugs

Open the hood of your ’70 Plymouth Hemi 'Cuda. The spark plugs are located in the cylinder heads, which are on either side of the engine block. Look for the thick ignition wires that carry the electrical current to the plugs—they connect directly to them.

Step 3: Remove the Ignition Wires

Carefully grasp the ignition wires by the boot (the part that covers the top of the spark plug) and twist gently to break the seal. Pull straight up to remove the boot without damaging the wire.

Step 4: Remove Old Spark Plugs

Insert the spark plug socket onto the ratchet and use it to unscrew the spark plug in a counterclockwise direction. Once it is loosened, you can remove it by hand. Inspect the old plug for any signs of fouling or damage.

Step 5: Check and Adjust Gap on New Spark Plugs

Using a gapping tool, check the gap on the new spark plugs. The correct gap for a 1970 Plymouth Hemi 'Cuda is typically between 0.035 and 0.040 inches, but consult your owner's manual to verify. Adjust the gap as needed by gently bending the ground electrode.

Step 6: Install New Spark Plugs

Thread the new spark plug into the cylinder head by hand to avoid cross-threading. Once it is snug, use the ratchet to tighten it. Be cautious not to overtighten; use a torque wrench to ensure it is tightened to the manufacturer’s specified torque, generally around 20-30 lb-ft.

Step 7: Reattach Ignition Wires

Reattach the ignition wires to the corresponding spark plugs. Push the boot firmly onto the plug until you feel it click into place, ensuring a secure connection.

Step 8: Repeat for All Spark Plugs

Repeat the above steps for each spark plug. The 1970 Hemi 'Cuda typically has eight spark plugs, four on each side of the engine.

Step 9: Final Check

After all the spark plugs have been replaced, double-check that all ignition wires are securely attached. Close the hood and start the engine to ensure it is running smoothly and efficiently.

By following these steps, you can check and replace the spark plugs on your 1970 Plymouth Hemi 'Cuda, keeping your engine in optimal condition.