Andy <adixon@loudoun.com>
wrote:Unleaded gas; Chevron's view
In response to a recent thread, I wrote to the customer service departments
of several gasoline companies. So far only Chevron (No financial interest,
Yadda Yadda Yadda) has responded. I guess unleaded is OK under the
"right" conditions. I'm pessimistic so I guess I'll go for the hardened seats
just to be sure.
Here's their response:-
"I am not aware of any inherent chemical properties of current unleaded
gasoline that would prevent valve seat sink under the "right" service
conditions in cars with valve seats that are not hardened. Nor do I
believe that many unleaded gasolines contain an additive to compensate
for the lack of lead. Chevron's unleaded gasolines don't. However, it
is Chevron's belief that using unleaded gasoline in older cars with
valve seats that are not hardened does not present a problem for most
types of service. This is should be particularly true for the light
service most antique sports cars see. Valve seat sink only becomes a
risk at higher than normal engine temperatures generated by operation at
sustained high speeds and/or loads. Please see our technical bulletin
on the subject at www.chevron.com/chevron_root/prodserv/index.html.
Happy driving."
Do with it as you will
Andy.
March 97,I attended the annual conference of the Federation of British
Historic Vehicle Clubs at the BMIHT Centre,Gaydon,Warwickshire,England.
The head Industrial Chemist from Esso/Exxon gave a talk about the impending
removal of Leaded Petrol/Gas from the UK on 1st Jan 2000 (that date again!)
She stated that there was no economical reason for any UK oil company to
continue to sell Leaded Fuel after that date,and it simply will not be
available thereafter.
But,our (LBC's) will run (in most cases) on unleaded fuel perfectly well.
Just so long as we do not exceed 55 mph under any circumstances,as over that
speed,the engine speed will most likely cause valve seat recession!
(oh terrific,so I have to drive my 180 bhp triple webered Vitesse,which I just
completed after 13 years,below 55 mph,until such time as I remove the cylinder
head and discover that the valves in my hideously expensive and beautifully
gas-flowed cylinder-head are too big to allow the insertion of valve seats!!!
(then I'm right in the Groop as the say in Holland!!!)
I've also had a very nasty experience with valve seats in an unleaded head I
had fitted to my Herald a few years back,they were professionally fitted by
heating the head casting and shrinking the seats in ? liquid nitrogen?,however
when the engine attained its' normal operating temperature,they fell out and
stuffed pistons etc...
That's not an experience I would wish to repeat.
However,I understand that there is an alternative method of fitting the seats
involving 'screwing' them into place.
Does anyone have any further thoughts on all this grief ?
Leon
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