My wife owns a 1986 Plus 4 with the Fiat 2-litre DOHC engine. This is
definitely not suited to unleaded fuel, and there is no way I could
ever persuade her to keep the revs below 3000 and never drive the car
for more than 10 minutes at a time. Thus ignoring the problem is not
an option, and I am sure that this would also be true for any other
Morgan driver. According to the AA, and some information I found on
the net(written by a petrochemical engineer), the available additives
are not all effective, and none of them are cost-effective. Also, I
would find it a bind to have to worry about carrying enough additives
for a long trip, so would prefer a "once and for all" solution. Having
spoken to a garage in Middle Barton, which was recommended by Fiat,
and to Guy Crofts former chief engineers, it seems that the conversion
involves changing the exhaust valve seats and valve guides (if they
are not already bronze). The inlets don't get so hot, so they don't
need changing. However, while you're at it, it pays to change all the
valve guides, blueprint the valves and have them ground on three
angles, and possibly have the head gasflowed. If you then use
super-unleaded, you shouldn't need any timing changes, and you should
see an improvement in performance, but you may be advised to use an
octane-booster in countries where you can't get super-unleaded fuel.
This can be a costly option, but it has extra performance benefits and
is sure to increase the resale value of the car, especially if it is a
low-number model like the Fiat-engined car (about 124 built). Of
course, the above may not apply strictly to other engines, but tuning
specialists are a great source of information on this subject. I tried
to get "horses mouth" information from Fiat in Italy, but haven't
heard anything yet. If you have a Ford engine, you may be luckier.
Roger Bennett
(whose wife has a 1986 Plus 4 which he is allowed to drive if he's
good.)
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