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Re: tyres & petrol

To: "Vodden, Dave" <Dave.Vodden@Telematics.com>, Morgans@Autox.Team.Net
Subject: Re: tyres & petrol
From: Howie <hclark@mail.dcwi.com>
Date: Mon, 17 Jun 1996 19:56:32 -0500
Hi,
Unleaded gas is a continuous source of discussion with old car folks.
Unleaded fuel will cause valve seat recession in a engine without hardened
valve seats i.e. valve seats in the cast iron of the head rather than in
hardened valve seat inserts. The recession is only a problem with engines
in continuous service, like buses or taxis or daily long-commute drivers.
I've talked to guys who have used non-leaded fuel and non-hardened valve
seats in their old cars for years without problems. 

I have an old Chevy truck with a 400 c.i.d. small block V8 that was rebuilt
without hardened valve seats in the early eighties. At that time, machine
shops were still a little wary of installing hardened seats as they
occassionally came loose. I've put about 70,000 miles on it and, although
it is getting a little seedy, it still runs fine. 

The rule of thumb seems to be: If you have remove the head to do a valve
job, by all means have hardened valve seats installed. Until that time,
don't worry about it.  




At 06:03 PM 7/15/97 PDT, you wrote:
>
>Chuck Vandergraaf writes
>
>>A second question concerns the use of unleaded gas in an engine that was
>>designed for leaded gas.  I've been led (no pun intended) to believe
>>that lead (Pb) in gas hardens the valves and that the replacement,
>>manganese (Mn), will eventually lead to problems.
>
>The issue is that the valve seats on older engines are not hardened.  Lead 
>in the fuel forms a protective layer, especially in the exhaust port.  Such 
>an engine will suffer valve seat wear when run on unleaded fuel.  I am not 
>clear on the extent of the wear, or on the influence of substitute 
>additives.
>
>98 Octane leaded fuel is still available in the UK as it was only in 1988 (I 
>think)  that cars had to be able to run on 95Octane unleaded and only in 
>1993 that CATs became compulsory on new cars.  Advice given by some 
>manufacturers (e.g. GM) for those who wished to change was to run one 
>tankful leaded in four so maybe an occasional treatment would be enough.
>
>Dave Vodden
>1992 Plus 4 4 seater
>Hampshire UK.
>
Howard Clark 
P.O. Box 413
Brookston, IN 47923
'65 +4 2 str
'36 Cord 810
'47 Ford Street Rod

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