Re: leaded fuel for fools

[Charlotte Udall <100662.3423@xxxxxxxxxxxxxx>]

>>That was my understanding also.  It served as a lubricant for the valve=
s.
>>That's why most pre 70's american cars don't have hardened steel valve
seats
>>in the engines and all mid 70's to current cars do.  Octane is needed t=
o
deal
>>with knocking due to timing right? Wouldn't that make lack of lead and
>>addition of octane fairly independent of each other?  How about Octane
ratings
>>in the 60's.  Were there any?  I wasn't around so I can't say.  =


Lead was originally added to fuel to provide a cheap method of raising =

the octane rating. However, its properties of protecting valve seats was
soon noticed and taken advantage of by those wishing to use cheaper
valve seat materials.

I have not heard of anybody having valve seat problems on an Alfa
which was definatly due to unleaded fuel. However, on some engine
(such as the old A series engine designed in the early 1950's) are =

particularly prone. Hopefully most Alfa's should need no more than =

an adjustment of ignition timing. European octane ratings are =

97RON for leaded and 95RON for unleaded which is effectivly a =

greater difference if the MON figures are compared. There is also =

a 98RON unleaded fuel available, but in the UK it is about 30% =

more expensive than normal  uleaded (although it is only maybe 1% =

more expensive in Belgium for example), which makes it around =

US$4.65 for a US gallon.

Compared to America, Europe has a far greater number of small
engined high revving cars and generally higher speed limits. The
higher revving engines impact on the valves seats harder and also
tend to have more radical cam profiles to again increase the impact
on the valve seats. It is widly claimed that below 3000rpm, valve seat
recession is not a problem, but as revs increase so does the problem,
and for example my Alfa 33 1.3 is geared to do around 4500rpm at
a normal highway speed (but runs fine on unleaded).

All the best

Keith

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End of alfa-digest V7 #399
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