How to adjust valve clearance on a 1970 Plymouth Hemi 'Cuda?

Maintenance of the valve clearance on a 1970 Plymouth Hemi 'Cuda is crucial for ensuring optimal engine performance. Improper valve clearance can lead to a range of issues such as poor engine efficiency, valve damage, or even complete engine failure. If you’ve noticed a ticking sound from the engine or experience decreased performance, your valve clearances might need adjustment. Here is how to solve this issue.

Step 1: Preparation

Before beginning, ensure the car is parked on a level surface and the engine is cool. Gather all necessary tools, including a set of feeler gauges, wrenches, and screwdrivers. Additionally, having a repair manual for your specific vehicle can be immensely helpful.

Step 2: Locating the Valve Covers

Open the hood and locate the valve covers. These are typically rectangular covers found on top of the cylinder heads on either side of the engine. In the 1970 Plymouth Hemi 'Cuda, they are metallic and have a series of bolts around the perimeter.

Step 3: Removing the Valve Covers

Using a wrench, remove the bolts securing each valve cover. Carefully lift off the covers to expose the rocker arms and valves. Be mindful of any oil that may spill and have a rag handy to clean up any mess.

Step 4: Rotate the Engine

To accurately adjust the valve clearance, the engine must be rotated to Top Dead Center (TDC) for the cylinder you are working on. Using a socket and ratchet on the crankshaft pulley bolt located at the front lower part of the engine, turn the engine. Identify TDC by aligning the timing mark on the pulley with the 0-degree mark on the timing tab.

Step 5: Checking the Clearance

Using a repair manual, identify the correct valve clearance specification for your Hemi 'Cuda. For intake valves, typically, the clearance should be around .028 inches, and for exhaust valves, around .032 inches. Insert the appropriate feeler gauge between the valve stem and the rocker arm. The gauge should fit snugly but still slide without resistance.

Step 6: Adjust the Valve Clearance

If the clearance is not within specification, use a wrench to loosen the locknut on the rocker arm. Adjust the screw until the correct clearance is achieved by checking with the feeler gauge. Once adjusted, retighten the locknut while holding the adjusting screw in place to prevent it from moving.

Step 7: Repeat for All Valves

Repeat the process for each valve. You may need to rotate the engine multiple times to get each cylinder to TDC. Ensure each valve’s clearance matches the specified settings in your repair manual.

Step 8: Reinstalling the Valve Covers

Once all valves are adjusted, carefully replace the valve covers. Ensure the gasket is in good condition or replace it if necessary to prevent oil leaks. Tighten the valve cover bolts securely but avoid over-tightening to prevent damage.

Step 9: Final Check

Start the engine and listen for any unusual sounds. A properly adjusted valve train should operate quietly with minimal ticking noise. If there’s excessive noise, re-check the clearances.

By following these steps, you can ensure your 1970 Plymouth Hemi 'Cuda's valves have the correct clearance, leading to optimal performance and longevity of the engine.