If your lucky and its a nice weber 45dcoe then they have whats known as an
'accellerator pump' mechanism.  This is so that if you suddenly put your
foot flat to the floor it won't let the cylinders run lean, it squirts a bit
of petrol down into the inlet manifold.  On a 1380 hill climb car I owned a
few years back the best way to start it was turn the ignition on, then the
electric fuel pump , wait for normal fuel pressure to be reached then prod
the accellerator about 5 or 6 times in quick succession.  This normally put
enough juice into the bores to start it easily enough on 11:1 c/r.  Not sure
if this is fitted to much older webbers mind.

Chris