dunno if you have seen this site yet, but the information is worth its weight in gold...http://www.tocmp.com/manuals/Carbs/Holley/H4000/C228/index.htm
That will give you quite a bit of information to troubleshoot that carb with. Sometimes it is hard to get an answer on this site with carb woes because of all the tricky details (as I'm sure you are finding out).
Have you removed the lid to the carb and inspected the fuel bowl and the lid itself?