Bob and Michael,
How 'bout a third opinion? My machinist tells me that unleaded is not
usually a problem until it is coupled with overheating. He says the
combination of no-lead and overheating will recess the valve seats in a hurry.
My experience seems to confirm this.
Other than that, I know nothing about it, but when I removed the head on mine
after 15,000 of no-lead, the seats were in perfect condition. When I removed
the head after another 15,000 miles, including some mileage (unknown amount,
but not a lot, certainly less than 1,000 miles) in an overheated condition, I
found three exhaust valve seats severely recessed.
I had no choice but to have hardened inserts added to those three, so of
course I went ahead and had the other three done as well while he was at it.
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74