only place in Phoenix i would use is Chucks Speed Center on Weldon Ave...
they have done great work for me, have always taken extra steps to make sure i was happy with there service.
i had a issue with a stuck valve/guide. i think it was the valves but they went and replaced all the guides with NEW bronze, hand honed them, re-did the valve job and bought valves... no cost to me...
i have heard good things about Eaton (somewhere in Phx)