[Bellerophon]

Dorien, something does not add up here, if you say that the car runs cool
and yet after standing with the engine switched off you are unable to place
your hand on the carburetors.
I take it that you have an original water pump with no thermostat so that
the water circulation with the engine stopped reverts to thermo-syphon. If
this is the case then there is something which is preventing the water from
circulating, because no way should the carburetor become too hot to touch.
If it was my car I would do two things before anything else, first remove
the water pump and check that all is well, second remove the radiator and
flush it out. This if it does not reveal a problem, then it will eliminate
possible problems in this area. If this fails then further avenues can be
considered, but do you have the SU or Solex carburetors and is the internal
oil cooler fitted.
My regards and good luck,
Bellerophon