What state are you in? I went with Wesbanco, they serve a smaller territory in the Midwest (I think it's OH, WV, VA, TN, PA, IN ?). For a 660, they'll only go to 80% cltv. However, they did pull Experian 8 non-mortgage score, maybe your EX is higher?
Figure.com will also do 660, but it's the absolute cutoff for an 85% cltv. I believe they pulled my Experian 9 non-mortgage score. The loan must be a first or second lien position.
Both of them do not have origination costs and I'd highly recommend either.
Also fwiw, I got about 6 quotes and none used a mortgage score for a heloc. Thought that was weird.
Edit: Thought it might be helpful to post my data for Wesbanco:
Mortgage Balance: $259,600
Wesbanco desktop Appraisal (no in person appraisal needed): $434,000
EX 9: 686
CLTV Max: 90%
Approved for their Flexline HELOC: $131,000 interest only payments for 15 years, repayment phase after that for 10 more years.
Rate: prime + 2% (6% at approval, but is now 6.75% with the prime increase. But I get a .25% discount for making payments with a Wesbanco Checking account, so it's at 6.5%)
Intro rate: .99% for 90 days
BK 7 discharged 6.5 years ago
