[Mgs] Unleaded fuel and Cylinder Head

[Rick Lindsay]

Hello LBCers,

Tetra-ethyl-lead did three things,

1) It elevated the apparent octane rating of the fuel to reduce ping  
   (pinking), predetonation and the possibility of run-on.  It did so
   by elevating the flash point of the fuel.

2) It left lead deposits on the surfaces of the combustion chamber, 
   including the valve seats.  That may have cushioned the valve-seat 
   collision but more importantly, that thin deposit allowed the valve 
   to 'bite' into the coating for a better seal.

3) It was argued that it put lots of lead pollution into the atmosphere.

   I have always viewed those aftermarket 'additives' as octane boosters, 
not compounds to replace the lead deposited on the seats.  It only makes 
sense that one would see no added protection to the seats if the actual 
goal was to tweak the octane.

YMMV.

rick

--- On Wed, 2/25/09, Paul Osborne <paul at ece.rochester.edu> wrote:

> Hello, just my observations on head rebuilds. Have done 3
> heads from various B and midget engines. New steel guides 
> and reground valves and cleaned up seat faces. the fuel
> being used in all of these is mid to high octane and have
> noticed no valve seat problems. These are cars that are
> driven as daily drivers in the better weather here in the
> north east.
> 
> paul