First I tried to re-tune my current carburettors to see if I was losing some performance here.
The first thing I did was check the carbs were all synchronised, but soon found that cylinder #1 was significantly down on airflow at both idle and high rpm, compared with all the others. Adjustment of the idle screw had no effect so I started to suspect an air leak on cylinder #1 manifold.
I decided to change that carburettor first with the newly refurbished one, and to recheck to see if that made a difference.
Once fitted both cylinder #1 and #2s airflow matched, and so I set up the new carb to match the old one still fitted to cylinder #3/#4.
One test drive later and the car is definitely transformed again, much smoother and definitely more powerful.
I then swapped the remaining carburettor over and retuned everything again.
Both newly refurbed carburettors fitted.
This time there wasn't much difference or improvement.
So in summary the main problems have been an air leak on the cylinder #1 intake and the incorrect throttle linkage setting resulting in less than 100% throttle.
The car is now transformed and drives really well - there may be more to be had from some further tweaking to the mixture - but overall I am really pleased with the results.
Thanks to everyone who has helped along the way.
