Humber sceptre 1725 cold start problems

[james78]

My dad has a sceptre it's been converted to unleaded petroleum it has a Webber carb all the ignition systems and electrical side has been replaced.The car won't start from cold it has to be warmed up to start.he has tried numerous solutions to the symptoms of the problem but to no avail.Just wanted to see if anyone had any ideas as to what may be causing the problem to start with as we are at a blank.Any ideas would be much appreciated thank you.

[CommerNut]

Good day,
My guess is that with the unleaded conversion your timing may be at fault. Setting it to the workshop manual specifications might be fine for the old leaded RON ratings, but not for chemically enhanced unleaded fuel.

This is an useful article to check:
classicmechanic.blogspot.fr/2011/05/ignition-timing-with-modern-fuels.html

Good luck