When British Leyland (BL) launched the TR7 the USA was way ahead of
the UK & Europe on trying to rein in vehicle emissions. By 1975
(as early as '73?) all new models had to run on unleaded gas - BL
were aiming the new vehicle squarely at the US market and thus were
watching the situation there closely (hence the fixed-head only early
models). The TR7 was also produced in a 'California' specification - a
wimpy 86BHP from a single carburettor, in order to meet very strict
emission controls imposed by that State.
The UK and Europe were lagging somewhat, in the vehicle emission stakes,
and no such controls on the use of leaded petroleum had yet been
introduced. So did the engines themselves differ?
Well no they didn't - the timing may have been tweaked, and the Carbs
setup a little differently to allow smoother running on unleaded juice
but other than that there was no significant differences. A quick check of
the UK parts list reveals that the part number for the valve seats is the
same as that of the US car. The valve seats must be hardened when running
on unleaded as the protective qualities of the lead is absent (the lead
in petrol is 'baked' in normal usage thus providing valuable protection).
It is therefore safe to assume that the UK spec standard 2.0litre head will
cope quite adequately on unleaded petrol without major modification.
What is clear is that LRP sold in the UK has not attained a British
Standard mark. Neither have any conclusive tests been carried out on this
flavour of go-go juice. In effect reliance on LRP to protect your
'leaded' engine is no more guaranteed to lengthen the engine life than running
on unleaded gas. If you are using unleaded (or will start to) it is worth
using a quality fuel - such as Shell Optimax - every few fill-ups.... this
does assist performance and is certainly a noticeable improvement on
standard unleaded juice.
Cautionary note: What may be worth noting is that
the unleaded petrol sold today is different to that sold in the
mid 70's - it is cleaner and may contain less protective qualities
than early lead-free varieties.