I think "master fitter" would be more accurate - bolts off old stuff and bolts on new stuff. Doesn't usually get too immersed in the oily bits.

Really?, you must be recalling different episodes of Wheeler Dealer than me, i can remember plenty of cases where engine components were repaired or refurbished by him.

He used to get more involved in the early episodes. He also used to send Mike "weakest link" Brewer off with a broken intrument cluster or ABS module and they would explain of specialist repair.