[Gearhead999]

Valve guide seals for sure. BUT.....the "C" & "M" engines were known for valve guide wear. If the guides are worn bad the seals won't last.

When you change the seals. After you pressurize the cylinders and pull the springs. Take a close look at the area where the valve meets the guides. You may be able to tell that the guide is worn and egg shaped opening now. If it is the heads have to be pulled and machined for replacable guides.

I'd replace the seals and see how it goes.