PSRU ever caused.

I'm not an engine guru, so what is the issue with 100LL fuel? My
recollection when the auto industry converted from leaded fuel to
unleaded, that it was the lack of lead that caused burned valves and
required different valves and valve seats. I do understand that higher
octane means a slower flame front. My guess is that the higher octane
in 100LL is keeping the combustion event ongoing long enough that the
exhaust valve opens while the fire is still pretty hot. Is this what
causes the valve problems? It can't be lack of lead as 100LL still has
lots, even with the "low lead" description.


Matt

You are dead on Matt. They Old Men were worried because the fuel
burns slower and burning fuel goes out of the exhaust valve. They
were worried that the valve would burn, so they did some things so
that wouldn't happen. It's in Jack's article in Kitplanes this month
(look on page 46).

I'm not an engine mechanic but what that article says is because of
this worry. They made sure they used a cam with a different profile
because GM provides that engine with six possibilities. You just don't
know what you are going to get.

They used hardened seats and stainless steel valves with chrome plated
stems, plus hard tips with bronze guides so nothing would stick and
freeze up on them using the 100 LL. Tom thinks that was all an over
kill but I have no idea. So, you'll just have to make your own
conclusions.

BWB