Quote:

Combustion temp is like 1500 to 1800 degrees. Again, 20 degree difference in the t-stat won't make a measurable difference in these cars especially at the typical hot rodder oil change frequency.



The point of the Continental Motors research long ago in the early 1960s,
and confirmed by later investigations,
is that at the end of the exhaust stroke the
"pore spaces" of the
ring land,
bore walls,
pistons,
head gasket gaps,
cylinder head combustion chamber,
are only a bit higher in temperature
than the coolant temperature.

These little 'caves' in the metal
now technically called 'quench clearances'
are cool enough
that mixtures of acids and water
can exist there as liquids
and cause corrosion.

It was a surprise to most
that the rust and corrosion in these little pockets
were the source of most bore wall wear.
It was a kinda breakthrough.

This struck me more than most people
because I am a mining engineer and
'quench clearances'
between metal parts
.... are the key thing that prevents explosions in mines.

You don't make things safe in mines
by making the electrical equipment cabinets
'airtight'
you make it safe
by making the walls massively strong and thick,
and by leaving ... on purpose
a special gap of limited size
that 'snuffs out'
internal explosions you accept will always occur
and keep this combustion from
'propagating'
outside to open air in the mine
where they sadly would become
man-killing explosions and fires.

This is pretty old technology
where Sir Humphrey Davie
in England in the early 1800's
won a national prize of
20,000 Pounds Sterling
for inventing the 'Flame Safety Lantern'

MPG improvement enthusiasts note:
these same 'quench clearances'
also kill off anywhere from
6% to 10%
of the fuel economy of an engine too!

Liquid gasoline droplets
'hide'
in the tiny 'caves' of the quench clearances
and either never burn during combustion
or burn so late that the dropping piston
has a bad angle to push against the crankshaft,
or even worse,
burn as the piston is trying to rise on the exhaust stroke.

This is why modern engines are going to
smaller 'ring lands'
more compact combustion chambers in the cylinder head,
and also one of several reasons that
polishing surfaces, or special coating,
of combustion chambers yield small improvements.

If you think to yourself:

"Hey, those little spaces are such a small percentage of the total space that there is no way they could make much of a difference"
..... then instead think:
a SCUBA tank of air at 3000 psi
holds much more than the SCUBA tank would at atmospheric pressure.

The key thing is that when combustion starts in the center of the cylinder head combustion chamber,
it generates very high pressures,
and these high pressures in turn:

"compress unburned fuel and air into the quench clearances along the outside edges of the chamber, especially the circular gap of the ring land"