Weird starting problem

No one seems to want to tackle this one, so I'll give it a shot for you. :) What carb are you running on that motor? My first thought is that the gas is evaporating out of you carb after sitting for a while. Maybe try priming it with a little fuel after it's been sitting for a while and see if that helps. I run an old Carter AFB on my 360 and I know they're bad for gas evaporation with the newer shitty fuel we get now, but I'm stickin' with my AFB! :) I have a switched electric fuel pump back near the tank running through the stock mechanical pump, so I can just hit the switch and let it run for a few seconds before attempting to start the engine, then a few cranks on the starter ususlly does the trick. Hope this helps.