SU Carburettor

[Pearls not a Singer]

I'm currently working on a fellow members car fitted with an 1¼ SU carburettor.

There are symptoms of fuel starvation (engine under load loses power for a few seconds then picks up again). I know that the zenith 26VA runs on 1½ p.s.i. but I suspect that a  SU electric pump would supply with a higher pressure.

Is this  a common problem when using an SU carb? and if so what was the solution?

Thanks in anticipation of a helpful discussion