How Much Vacuum??

Thanks for the replies. The engine is already together and on the road. It runs great and seems to want quite a bit of initial timing. It's at 25* now, but seems to want more. It's got RHS heads and with 1.6 rockers, so theoretical lift is at .561". It idles great at 750, but only seems to pull 6" vacuum in gear at 750. I just thought that seemed a bit low. I don't have power brakes or anything, just wonder if 6" is all it has.