This article is from the Lotus Cars FAQ, by email@example.com (Alan F. Perry) with numerous contributions by others.
From Dave Van Horn (firstname.lastname@example.org):
You should budget for an engine rebuild roughly every 50K miles.
Certainly the head will need going through by then, since the short
valve guides wear quickly and start leaking oil into the cylinders.
The water pump lasts only about 25-30K miles. The short drive
belt => high tension => high stress on the pump pulley bearing.
From John McLaren (email@example.com):
The rear suspension uses the prop shafts as part of the load
carrying structure. It is vital that the correct shims are fitted
between the inboard drive yokes and the gearbox output. No shims
result in the axial force being exerted onto the roll pins securing
the yokes to the gearbox splined shaft. This results in eventual
destruction of the differential bearings, breakage of the roll pins
and/or wearing of the splines. The problem can usually be detected
early by checking for play in the rear wheels when the car is jacked
up (suspension at full travel).
The engine always tends to overheat, even when the water pump is in
good condition. I found that removing the water thermostat and fitting
a more powerful electric cooling fan worked wonders (although I only
run the car in the summer months).