What are possible causes for delay in starting?

Probably comes down to properly tuning the carb or timing, but my mild 69 318 now with 4bl intake, a 600 (i think) holley and rv cam is slow to fire. oh yeah it has an orange box MP electronic ingnition too.

Seems to have gotten worse here lately. When the engine is hot...no prob turn the key and it fires immediately without touching the pedal...but if it sits for more then 5 min it takes an awfully long time to fire up.

Would greatly appreaciate any advice on where I start and sequence of tweaks so I can sort this out...
1) retard or advance the timing
2) air/fuel mixture lean it out or richen it up

Many thanks
Steve