74 Dart 360 Sport

So I have read that total timing on a HEI is 60 this cannot be right out of the box. I had set it at 10 so I thought but will only idle if vacuum is unplugged from distributor. At my wits end on this final crap here about to take it some where if need be. Basically I cant seem to get the timing right with vacuum connected, it idles fine with it disconnected now so I think I can hook it up little worried it will go back to running way rich and fuel wash my stuff ruin it.