hi, i have a datsun a15 with dellorto dlha40 carburetors

known mods:
~porting on the inlets, a bit bigger than a12gx ports
~4-1 headers
~the carburetors

it seems to be over fueling, sooting the plugs and blowing a bit of black smoke.

does anyone have a similar setup to this and what jets are you using and are they suitable? If you have an air-to-fuel ratio reading that would be very handy.

thanks very much