I have a problem with my Holley 600 (4160)

Hmmmmm... I have a Performer intake, 67 barracuda, and 750 Holley WITH a 1" spacer and my hood closes fine. I had fuel percolating problems until I added the 1" spacer. With drop down air cleaner. I have the thinner motor mount insulators if that would make a difference.

These work amazingly well and they aren't that thick. Also you might consider pulling that intake and blocking those heat cross overs too.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL-9265&N=700+115&autoview=sku

or if you want a center divider type:

http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL-9266&N=700+115&autoview=sku
do what these guys are saying, check your fuel line routing and insulate it, use a phenolic/plastic carb spacer or one of these rubber base plate gaskets and a drop down air cleaner. You shouldn't have to pull your intake. check your float level too, if its too high it, when it gets hot it will reach high enough to get to your idle circuit and flow down into your intake. (vapor lock)