Clackety Clack (TR6 valves - 2 questions)

[jim.sudduth@autodesk.com]

     Hi Fellow Listers:
     
     I recently did the head on my '74 TR6 and had the hardened valve seats 
     installed for unleaded gas. I also replaced all the valves, guides and 
     valve springs, so this puppy is like new (I hope...).
     
     My problem is that I can't seem to get the valves to be as quiet as 
     they were before. I've adjusted them numerous times and checked and 
     rechecked the head and rocker arm shaft torque. After I adjust them 
     they're quiet for a few miles then they get noisy again. 
     
     Should I expect the hardened seats to cause more valve noise than the 
     stock ones?
     
     Also, I've heard that cam, lifters, pushrods and rocker arms "wear in" 
     together when an engine is new and shouldn't be replaced except as a 
     group. Is it ok to replace the pushrods and not the rocker arms and/or 
     lifters? 
     
     Thanks,
     Jim
     jims@autodesk.com
     '74 TR6 CF20076U