Fitted one of these club cassis electronic ignition, fantastic low end and smooth idle, lost 5mph of top speed as expected. Problem : No matter how much I retard the timing I can not stop pinking in the mid range.
650 big bore and ecas/ bourbor exhaust.

Have you fitted larger jets? If running on standard jets will pink especially with blower kit....

Mark,
what amount of total ignition advance are you running?
I don't know what the target compression ratio is with Burton's 652 conversion, but if it's 9.0:1 or higher, I'd guess that you should not be running much over 30*.

Also, which grade of plug?
If they're NGK, a plug with the originally recommended heat range of '6' will be too hot, I'd recommend using an '8', as in B8HS or equivalent.

Thanks, all yes burton big bore & jets. Was all fine on points no problems other than a slight low spot at around 2500 to 3000 rpm. Electronic ignition cured this flat spot, better starting low torque.
Have been running points at full advance , marks on flywheel set with strobe since 1997.
Set up as club cassis instructions the electronic ignition is a good tooth (retarded) out from my timing marks, I have retarded it to the point of rough idle & still pinking if I put my foot down 3000 to 4500 is rpm range. Now I have lost 15mph off top speed!

Does smell like it is running rich.

How old is the MCC ignition?, would suggest thoroughly checking timing dynamically.

Bought new at Christmas, I suspect this would be fine on a standard engine but the curve is wrong for my modified engine. Is it feasible to set my own curve on this ?

15mph off top speed?
That's a huge reduction in power, assuming that 'top speed' was above 70 mph, so perhaps the ignition setting you've got is too retarded?
That will cause the engine to run very hot, possibly to the point that detonation will occur.

As Roy has advised, worth a thorough check of the timing setup, maybe even revisiting your 8* BTDC mark...

Thanks, yes I have deliberately over retarded the timing in an effort to stop pinking in the mid range. I thought that only overly advanced timing causes pinking, i didnt realise overly retarded timing also cause pre detonation.
Temperature gauges indicate it's not running hot.

I would go back to points straight away as you are about to make changes to your engine that where not there before mounting that ignition.