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I have recently received back my XK120 Replica Aristocat from mechanics. While I am please overall, there is still a problem with even modest acceleration being sluggish it's still troubled by a backfire! The car has triple 2" HD 8 carbs with the fabled AED choke. While the car was away I purchased a set of 2" HS 8 carbs complete with inlet manifold and a manual choke adaptation. I am not a mechanic but the swap is pretty basic I think. So do I take the plunge and go for fewer (twin) carbs option, ditching the auto choke to give me a smoother ride? I am a sedate and not a power driver so for me three carbs is an ego trip only.

The valve timing, clearances, ignition timing, mixtures, or a combination thereof must be incorrect if the acceleration is sluggish and accompanied by backfiring.
Look for air leaks / vacuum pipes disconnected to start with; the cheapest and easiest thing to fix.

I have recently received back my XK120 Replica Aristocat from mechanics. While I am please overall, there is still a problem with even modest acceleration being sluggish it's still troubled by a backfire!...

Probably far too late to be useful, but have you checked the damper/dashpots on top of the carbs are full of oil? I think you're supposed to use SAE 30 or some such monograde oil, but I always used engine oil as it was handy. Without it, the mixture weakens under hard acceleration, and AFAIK that causes backfires.

Never too late Paul. Many thanks

The valve timing, clearances, ignition timing, mixtures, or a combination thereof must be incorrect if the acceleration is sluggish and accompanied by backfiring.
Look for air leaks / vacuum pipes disconnected to start with; the cheapest and easiest thing to fix.

Very welcome input I went through each of these and paid particular attention to the timing and distributor setting. She is purring again thank you