Oil pressure

Inside the oil pump housing.

The chain case cover is the oil pump housing. The relief valve is in the bottom of that housing. After removing the oil pan, there is a cap to remove. You do that by drilling a 1/8" hole and threading a self-tapping screw into it to pull on.

Sorry for the delay. High winds, trees down, power out, 'puter dead until a few minutes ago.

To see the cap you have to remove the oil pan. The service manual instructions say to remove the chain case cover so you can put the head of the self-tapping screw in a vise to hold it while you tap on the cover to pull the cap out. That MIGHT be necessary, but I would be looking for a way to do that with the cover still on the engine.

The perfect tool for the job would be the tool used to remove broken pivot pins from a tilt steering column. It is a tapered threaded screw that goes through a mounting block, and has a nut that when tightened, pulls that screw out. You might be able to do the same thing by using a vise grip pliers and hammer to tap the cap out.