Start by performing a compression test on all cylinders, if #1 and 4 are low, then possible rings, or valve spring.
As Raz mentioned could also be valve stem seals or guides. The valve stem seals (if bad) you would have blue smoke out exhaust on startup, if rings it would smoke all the time to some degree, but a compression would tell you if rings are bad.
This could also be a tube seal that is leaking oil into spark plug hole, if you remove plug and tube hole is covered with oil then a tube seal is leaking, this is a $100-200 repair.
If rings are bad, then you would probably be better off replacing engine with used one.
If seals are bad, you are looking at $300 to replace. If guides are bad, I would replace head with a remanufactured one, usually cost $300-600 plus labor to install.
Sunday, January 17th, 2010 AT 7:47 AM