Hot running problem, 1990 460

[Rainbird]

I've got a 1990 460 1.7 with a carburetteur. When the engine gets hot it misses. This is particularly the case after sitting in traffic. When it's cold it runs perfectly so it's not a dirty fuel issue especially as I've put in an extra filter in the fuel line. Also, once in clear traffic and it sorts itself out and runs fine

Could this be a heat soak problem resulting from a silted radiator causing fuel vapourisation in the fuel line? My old Range Rover had a similar problem with heat vapourising the fuel after a run, but they are known for silting the rads. Are 460s known for this problem?

The other thing I was thinking about was to do with the fuel pump getting hot and sticking due to thermal expansion, especially as it's at the back of the engine where temperatures are likely to be highest.

Does anybody have any ideas?

Many thanks
Peter