It sounds as if you don't have the right walking foot for these machines. They would take a low-shank foot such as this one:
http://www.ebay.com/itm/SINGER-Even-...-/370613789188
They would not take this one:
http://www.amazon.com/Singer-Even-Fe...dp/B002EZRV4C/
The vintage machines did not have built-in anything! Darning foot is a separate foot, as is the walking foot.