Pro/e (Creo) Valve/ Valve seat hard stop mechanism

Hey guys, I'm having a problem figuring out how to constrain a valve/ valve seat mechanism. I don't know how to constrain the tapered surface to stop against the valve seat. :/

http://img.photobucket.com/albums/v4...nder/valve.jpg

I have the valve move with a cylinder constraint. can't use a pin constraint, since the valve won't move then. I can't use a cam connection, since it won't let me select the tapered surface.

http://img.photobucket.com/albums/v4.../valvepair.jpg

So I'm trying to get all these linkages to move together, and this is where I'm stuck.

http://img.photobucket.com/albums/v4...lvelinkage.jpg


and some eye candy :P :

http://img.photobucket.com/albums/v4...top_render.jpg