Jim---I have been running unleaded fuel in my '73 for at least 100,000
miles, and have had no problem with valve recession. I never use
additives. If the valve lash isn't getting smaller, the seats aren't
being beaten in, in any significant amount. (The valves were ground
about 60,000 miles ago, and the seats had minimal wear.) It's good to
check the lash often enough to get comfortable that you're not losing
the clearance here, which of course could lead to burnt valves, should
one or more not close due to recession. Heavy valve return springs, such
as used with competition cams, may compromise this somewhat.
Dick Taylor
|