It's the cold air,( and that is relative seeing it is ambient
temperature air from within the engine compartment, but much cooler
than combusted (sic) air), anyway, as it is sucked in through the leak
it hits the exhaust valve and the mix of that and the heated air
already in the combustion chamber (not all burned gassed air is
exhausted) will cause a hot spot or a heated valve that is exposed to
the little blast of cooler air that will react into , over many many
RPMs, as a cool spot. Like blowing on burning embers in a fire place
to get them to flare up. The main problem with this phenomenon is that
that cooler air is hitting the back side of the valve face, ie stem
and seats area and not the valve face, giving those weaker pieces of
metal a certain amount of fatigue. It never has a chance to cool down
as the engine is running and because of that can burn the metal of the
valve or stay continually hot enough in stop and go driving that it
can cause detonation either prematurely or down into the exhaust
runner in the head....ending with burned valve, valve seat, stem and
valve guide. That's the long way around. ERGO, the need for gaskets
that seal....did I mention top of piston , especially with any carbon
build up over the years. All intake and exhaust gasket leaks must be
dealt with ASAP or as a result you could end up replacing more than a
few parts.
On Sat, May 29, 2010 at 10:54 AM, Eric <huffy340@gmail.com> wrote:
>
>> In Addition, being an exhaust port, on the down stroke of the
>> piston cooler air can be sucked in through the leak and put a hot
>> spot on your valves.....that can cause them to detonate
>> prematurely and burn valve as well as top of piston
>
> Would you explain that a little more? What's causing the hot spot?
>
> thanks,
> eric
>
>
--"The reason dogs have so many friends is that they wag their tails instead of their tongues"
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