[Bellerophon]

Well Rubbond, The 2 litre Bristol engine does not have an inlet manifold,
it does have an inlet tract where the carburetors are bolted direct onto the
cylinder head.
All fuels are not the same and some burn at a slower rate than others, so
if you have one of these in your tank you can still have burning fuel
entering your exhaust manifold, and thus end up with a very hot manifold.

Modern fuels are only intended to stay in your tank 3 or 4 weeks maximum,
after that they start breaking down into their various parts (ethanol)
which can eat away at components such as the old type of petrol pump diaphragms.
If you have one of these change it to a modern resistant one or you may
suffer the same thing I did on my way to Scotland. Although my engine kept
running a hole developed in the diaphragm which allowed petrol to fill up my
sump and resulted in an engine rebuild.
My regards,
Bellerophon