The information from Kipping is actually from an article that sits
on the Team.Net ftp site. I am reproducing it here. It can be found
at ftp://ftp.team.net/sol/valves.txt.
And yes, I am related to the author, he is my dear old Dad.
Doug Mitchell
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The problem of valve seats in internal combustion gasoline engines
became apparent with the gradual fazing out of leaded fuel in the
late 60s and early seventies. Lead in the fuel accomplished more
than increasing the knock value of a fuel. When the auto companies
began testing "virgin" engines with unleaded fuel, valve seat
failure was encountered within 10 to 20 hours during a wide open
throttle 4000 rpm durability test. Lead in the fuel provided exhaust
valve seat lubrication and excellent heat transfer from the hot
exhaust valve to the seat in the head than to the coolant media.
Several methods were tried including seat inserts. valve rotators,
and cooled valves, either sodium filled or a "heat pipe" design. I
ran all types of designs including the "heat pipe" and also with a
jet of coolant (water) sprayed directly on the valve. It became
apparent that keeping the valve cool was a good solution but costly.
The hardened valve seats became a cost effective compromise and was
adapted by most if not all of the manufacturers. With the effect of
unleaded fuel under control, the next step was to incorporate a
catalytic converter to reduce the level of CO and HC. A catalyst
reacts very quickly to an increase in unburned fuel causing a
catastrophic catalyst failure within microseconds. Thus it was
apparent that the then widely used breaker point ignition systems
in use would allow the engine to operate, although poorly, and cause
a catalytic catalyst failure. This began the expedited development
of a breakers or electronic ignition distributor, referred to as a
"walk home" design since if the distributor began to fail, the
engine would stop preventing any costly catalyst damage. With the
advent of relatively inexpensive on board computers, electronic fuel
injection was introduced as well as non rotating ignition systems all
receiving inputs from sensors located in strategic necessary location
sensing temperatures, fuel mixtures and exhaust makeup.
First, there never was a "requirement" for valve seat treatment,
it was up to the particular automobile manufacturer. Further, I
mentioned valve seat failure (valve seat recession) on a "virgin"
engine. If the same test was applied to an engine that had been
run with leaded fuel, the valve seats did not fail. There is a
sufficient quantity of residual lead in the system affording
protection and very few engines are ever subjected to the durability
type test that produces a valve failure. In the case of your Triumph,
you should encounter no problem using unleaded fuel. In the test that
I mentioned, valve seat recession measured 0.000150 to 0.000180 of an
inch in 40 hours of wide open throttle, 4000 rpm operation. Incidentally,
valve seat inserts are not a good solution because of the expansion
differences and the tendency for the seats to loosen - staking the
seats only aggravated the situation in the long run. Hardening the
seats was a good compromise (the depth of hardening is only .030 or
so). Enough said!
>From B. John Mitchell, 15 March 1996
(Mr. Mitchell retired from GM in 1975 after 37 years. He was involved
with engine development during his tenure. One of his more well
known engines was the Buick aluminum V-8 designed in the early
1960s and still in production today as the Rover 3.5 family. He
was also involved in the development of the current Buick 3.8L
engine.)
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-----Original Message-----
From: Catchpole, Pat [mailto:Pat.Catchpole@ntc-europe.co.uk]
Sent: Wednesday, December 19, 2001 6:03 AM
To: spitfires (E-mail)
Subject: RE: UK/Ireland LRP question
The AA website ( www.theaa.co.uk ) has a list of all garages selling LRP,
but I have not checked if this covers Ireland. Have you tried the petrol
co. websites?
If you are only covering a few miles a year though, John Kipping's old
advice about just using regular unleaded probably applies. Apparently on
old cars the valves have accumulated enough lead over the years for it never
to be a problem wearing off.
Pat
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