<snip>ducantibruce I thought these cars were designed to run on unleaded though. Still I do acknowledge that there are probably other ways that modern fuels differ. I am wondering if using something like BP Ultimate 98 octane would make a difference?
Designed to run on unleaded, in that they have hardened valve seats. Lead is an upper cylinder lubricant as well as knock inhibitor.
Modern ULPs have a vast number of additives to achieve the knock inhibitor properties of leaded fuels. Most of those additives are highly volatile. They also mean that the combustion process changes quite a lot between a cold & hot engine. Modern electronics use ambient as well as engine temp in addition to a whole bunch of other parameters to determine appropriate ignition timing. Our poor old Marelli/Bosch distributors can't do that.
Timing that's optimised for hot running will be less than optimal for cold starting.
Modern ULPs additives are also quite volatile in that they evaporate quite quickly. Modern EFI's are pretty well air tight and don't allow much evaporation. Dellortos & Webers are anything but airtight. Parked hot a lot of the volatile compounds evaporate from the carbs quite quickly - leaving a vaguely fuel like fluid. Part of the long starting process is getting fresh fuel into the engine to replace the old stale stuff.
The guy who gave me this info (about 10 years ago) was engaged in developing tests to check for mandated retail pump fuels in motorsport. His basic recommendation was that modern fuels were so variable over time (same brand/batch even as it aged) that it was next to impossible to test for cheating & proposed a max octane rating as the best derterminant.
At that time, & with the fuels tested the BP was most consistant (& therefore probably least volatile) whilst Shell was most variable & volatile.
The higher octane ULPs have more volatiles than the lower octanes & will probably (if I'm right) make the problem worse. FWIW I run the BP ultra 98 for various reasons & put up with the harder starting when cold (which is worse the longer the car has been parked(up to about a week))
None of this is to say your 105 should be really hard to start cold, just that it will almost always take a bit more than when it's warmed up