M8 Harley Oil Pressure Relief Valve

Here is a great tech tip that Mike demonstrates for any members who are working in their cam compartment.
It is always a good habit to remove, clean, and inspect the M8 Harley oil pressure relief valve any time work is being performed within the cam compartment. Especially, if there had previously been some type of catastrophic damage that left a debris field within the motor. The relief valve was previously located in the cam plate on Twin Cam motors. Now the M8 Harley oil pressure relief valve is located in the oil pump body for all Milwaukee Eight motors.

The M8 Harley oil pressure relief valve assembly consists of only a plunger, a spring, and a roll pin. A specialty tool is needed to disassemble & reassemble. However, the tool is something that is not difficult or complex. You can easily make it yourself. If you prefer to purchase the tool, it will typically cost around $50. It can be purchased from Jims Tools USA.

To disassemble the M8 Harley oil pressure relief valve, use the specialty tool to depress the spring and tap out the roll pin with a 1/8″ punch. Keep a firm grasp on the tool so that the spring does not shoot out, across the room. A small magnet can be used to extract the plunger from its bore in the cam plate. Now, all you need to do is clean the plunger, the plunger bore, and the spring. Coat the plunger with clean motor oil and verify that it can slide smoothly within its chamber.

To reassemble the M8 Harley oil pressure relief valve, simply work in reverse. Slide the plunger and spring into position. Depress the spring with the specialty tool and tap the roll pin back into its original position.

Inspect the oil pressure relief valve every time you are in your cam compartment.

Twin Cam Projects:
Cam Chain Tensioner Shoe

Cam Gear Drive Conversion