The Blues take on Wanderers on Bromley's Hayes Lane artificial playingÂ surface, with the winners securing a third-roundÂ date with Premier LeagueÂ Liverpool.
Cray are already on their best run in the competition, but Dacey is hopeful his troops can progress even further.
Pompey's youngsters reached the second round with a thumping 5-2 triumph over Bristol Rovers, while Wanderers were winners at Worthing.
And Dacey is dreaming of clinching a trip to Liverpool by dumping out the Blues.
He told Cray's official club website: 'It's going to be a great occasion for the club, hopefully we get a decent crowd in to support the boys.
'We are fully aware they will be a very good side but we aren't a million miles away from that level either, in my opinion.Â Â
'We have absolutely nothing to lose in this fixture but we are going in to the game fully looking to win.
'˜Hayes Lane is a very difficult place to come, not many like the 4G.
'˜It's something I'm assuming Portsmouth won't be used to.
'Both clubs realise how big the prize is for the winner. For most, if not all, the chance to play Liverpool on their own patch is just a dream.
'˜To be one game away from it becoming reality gives you goosebumps.'