>The worst vehicle for VSR that I've encountered was......my 1971 MGB/GT! I
>surmise it isn't too far evolved from the BMC A series. Now it has stainless
>steel exhaust valves and stellite exhaust seats.
>
Indeed it would be, the B Series in this vehicle is virtually only a drawing
scale-up from the A series to make a nominal 1800cc engine.
>Just for good measure, I run a little 100 octane aircraft fuel through my
>old cars periodically. I don't like to run it straight up though, too much
>lead fouls the spark plugs- and it's expensive, nearly $1.89 per gallon
>(Let's not start that thread again!).
>
The only thing we recognise over here is 100LL AVGAS, where the LL stands for
low-lead; this is becoming hard to get even for the light aircraft people in
the know. A discussion with the Chief Scientist at Associated Octal, a classic
car owner himself, I learned that the quantity of TEL required to protect
exhaust valves without any octane boost effect is tiny and far below the actual
levels of the current pump fuels. The effect of the TEL lasts for something
like 500 miles when running on unleaded fuel alone so an admixture of leaded
AVGAS and unleaded fuel now and again will apparently provide protection.
Surprisingly some original 1940's MV manuals here specifically refer to the
different plug and engine internal presentation when run on leaded fuel and
reassure the mechanic that this is expected and not symptomatic of a fault, the
_inference_ being that unleaded was the norm.
We hear nothing of the MV scene in NZ, if it exists at all, but rumours
continually received suggest they are to re-introduce very low lead fuel as the
pollution budget favours engine efficiency over production processes to make
similar lead free fuelled engines. Perhaps our Aussie friends nearer the action
could comment.
Certainly a recent discovery here of pre-Roman (lead pipes), extensive and well
preserved human remains showed on analysis entirely the same levels of lead
absorption as for the present day, after that gem escaped from the labs we have
been told nothing further, suspiciously.
For those of us struggling under the delights of the money hungry, bureaucratic
dinosaur known as the EEC, member nations are permitted 0.5% of total sales to
be leaded fuel to current specs, some 109,000 metric tons per year for the UK by
1998 figures. If any of the oil companies choose to make it and how you come by
it is another matter entirely.
Incidentally the octane rating alone tells you very little about fuel
properties, AVGAS is low volatility and necessarily resistant to vapour locking
or carb icing. Octane ratings are derived using a standard, single cylinder lab
test engine with variable compression, the sample fuel is run with increasing
compression figures until the onset of knocking and detonation. At this setting
the engine is re-run on lab fuels, cetane and heptane, one which always
detonates and one which does not, the proportion of non-knocking element added
to just preclude the effect gives the rating.
Thus the figure cannot exceed 100 and any rating over this figure must have TEL
added and the last two digits represent this added amount in decimals of a
milligram per litre I think.
Richard
(Southampton UK)
===
To unsubscribe from the mil-veh mailing list, send the single word
UNSUBSCRIBE in the body of a message to <mil-veh-request@skylee.com>.