For my first car, my parents gave me their elderly Chevy, which had a "stove-bolt" I-6. It needed a valve job (possibly from failure to adjust the valve clearances after its ring job of 40K miles earlier). I took it to a local country mechanic. Including one new exhaust valve, grinding the other 7 valves, and a new heater hose, his total bill for parts and labor came to something like $40. Afterward, it ran well as long as I kept it. I realize there has been a lot of inflation since then, but not THAT much! More modern engines do normally have the compensating advantage of needing such repairs less often, so I'm curious what cause CarlD will find.