leaded/unleaded

[Phil Waterman]

Michael- You ask a very good question about valves and lead or lead substitute and Lang I think hit the nail on the head. It depends on how hard the engine is run.

My experience is limited to this issue as it impacts Chevy CMPs. I've been driving my HUP since 1980 that's 30 years and the engine has never been apart and the head has never been off. No problems and I have not used the lead additive. With the HUP you do not run it at full throttle very much of the time.

But with my C60S I did have valve wear problems with valve recession, actually meaning that the valves had to be readjusted about every 2 years (2000 miles) as the clearance would gradually disappear. When clearance goes to 0 the end is quick see http://www.canadianmilitarypattern.c...edvalve6x4.jpg for what happened in one trip. Once the valve doesn't close all the way or has a small bit taken out the flame cuts the valve quick. (When the valve burnt I had a vacuum gauge mounted and in one trip it went from normal to needle bouncing of the peg.)

The problem with the C60S with the radio body was that it had two throttle positions "on the floor" or "foot off the pedal". Because of the weight and non aerodynamic shape the engine basically spent its life at full power.

The fix for the Chev Stove Bolt 6s seems to be installing modern exhaust valves. Once that is done the valve wear seems to go away.