Something is causing pressure to build up in the crankcase. There are a number of possibilities ranging from the worst being loose pistons and rings (called blowby) to something as simple as a plugged or restricted pcv valve. It could also be a leaking head gasket. Where compression is leaking into an oil passage. A more common headgasket problem would be when compression leaks into the water passages which would cause overheating and bubbling in the radiator. Another possibility although less likely would be a severly restricted exhaust system.

Since you are getting oil in the air cleaner I am assuming that there is a hose connecting the crankcase to the air cleaner. Most likely from the valve cover. Also the fact that the dipstick is being pushed out is another example of excessive crankcase pressures. These pressures can be so great that they will actually blow valve cover gaskets.

A simple test to check for excessive blow by is to remove the pcv valve while the engine is running and watch for oil vapor excaping the pcv valve opening in the valve cover. You can also place your hand over the opening and see if you feel any pressure against your hand. It is helpful to rev the engine slightly while holding your hand over the opening.

If you do experience excessive blow by you may help your situation out for a while by using a PCV valve for a Ford 460 engine. I have done this in the past on a T-Bird V6 and a Tempo 4 cyl. that were both basically worn out and it solved the problem of oil in the air cleaner on the T-Bird and blown valve cover gaskets on the Tempo.

I hope you just have a bad PCV valve.

Daryl