I don't know but they say the old models with cams do some great stitches. I've heard some people keep old Singers just to do buttonholes with the cams. Hope you can figure it out.

According to someone on patternreview.com New Home may send you a manual if that helps.

Here is a link that might be useful: patternreview website

I have a New Home model 534. Older than yours, a 1963 model. Mine doesn't have a cam for overcasting. They're all decorative stitches. I looked at my manual and overcasting was done with the zigzag stitch. The tension needs adjusting to eliminate the pucker you get when the edge of the fabric is pulled tightly in. I never used it as the hassle to adjust the tension to overcast and then back was more than I wanted to do. I just always used a stay stitch around the pattern pieces instead. Never had a problem with ravel beyond the stay stitch. Yours may indeed have an overcast cam as your model is later than mine.