Facing the eventual necessity of a valve job and head replacement, I would like to make the 915s I purchased a year ago serve. To my knowledge, these have not ever been prepared for use with unleaded petrol, and I wonder if investing in hardened valve seats for these will be warranted. (I doubt if the old 516s I currently run have ever been so prepared either.) MOST (over 90%) of my driving is urban, and even on the highway, I RARELY turn the engine over 3000 rpm.
Given such...
Hardened valve seats for iron heads; worth it or not?
