This theme is a old round-around on the board, I write this message on benefit of new fans and members:

In the 1800 forum you can see a discussion about valve recession:

http://www.brickboard.com/RWD/index.htm?id=652579

JohnMc make a good resume on it:

"The general consensus seems to be that a head that was weaned off leaded fuel has a work-hardened face that will last very well indeed with no additives. Once that surface wears off (a normal valve job would do it immediately) it will wear down pretty rapidly. Also, high rpm use will also wear through that layer more quickly as well. The octane isn't (AFAIK) a factor in valve wear. Proper valve lash adjustment, however, is."

Also, on the following url you can read a good explanation about the sources of seat recession (at last, it make sense):

http://www.airheads.org/index.php?Technical%20Tips+Airhead%20Valve%20Recession

(the article is about valve recession on motorcycle engines, but we shared the same problem and the same principles apply).

As usual, my excuses for my spanglish.

Joaquin Novara
Rojo 121 Amazon
Lima - Peru
http://www.volvoadventures.com/121spec.html