My bracket 400 stroker 505 C.I. motor is right at 15.0 to 1, I use the local pump E85 and check it for the actual percentages, they vary from 85 % all the way up to 89 percent after sitting in the plastic fuel jugs in the race car trailer
I'm getting ready to go dyno test and break in the new bracket motor this week and I'll use the fuel in the jugs left over from last year, I'll check it and maybe I'll jet it up to see if I can get it rich enough to loose power
The first time I dyno a motor I bought E85 from the same station in early fall six years ago, they had ordered winter fuel that ended up testing to be 75%
All the fuel I've bought from them since then has tested to be 85%
I have found that my bracket motor does NOT like cold spark plugs