Originally Posted by
Lead Balloon
You (and many others) confused correlation for causation.
Removing the lead from the fuel meant that the lead was no longer in the fuel. That caused an increase in the probabilities of detonation in engines that were not designed to run on unleaded fuel. Detonation causes a disruption of the boundary layer inside cylinders that usually helps to insulate them from being exposed to all of the heat generated by the combustion event. That’s why ‘heavy’ detonation causes an increase in CHT (and is what is causing the problem in mustering chopper engines).
I think you’ll find that what actually caused the rapid valve seat recession in car engines when lead was removed from MOGAS was detonation/high CHT.
Once again not quite true. Whist the boundary layer protects the top of the piston detenation will at the extreme will and can blow down the side and top of the piston. It also damages the small and big end bearings and can even bend the con rod. Light detenation will damage plugs and cause errision in the chamber and top of the piston.
Damage to car engines valve seats when lead was removed was that most cars up to that period didn’t have hardened valve seats as they were part of the head casting and machines out of the parent material.
To get around this problem hardened valve seats were used in both alloy and cast iron heads. It had nothing to do with high cht as the water cooling system in a car is far more efficient than air cooling.
Stick to your day job !!!!!