dave, please dont go to any hassle. use your free time wisely! (ie not pulling a head of an 18rc)
if it comes to it, i too can find a wreckers and go pull a head apart. im just lazy and if someone has got some *just lying there* well, it'd be a crime not to take them.
if, on the otherhad you have a deep seeded desire to flee the house and bury ones self in a car at the wreckers, who am i to stop you? but please, dont spend too much of my money?!
hell, i dont even know what valves cost, but if theyre going to be more than say $20 dont bother.