Since I added 30% E-85 to my '69 440 10:1 engine
I'm able to add 5 degrees more timing with no ping. I also used E-85 in my '81 Kawasaki 440 8:1
motor and it stopped the pinging that it has had since day 1, even though I use 93 octane. No timing change. Finally I used it in my 25 year old
Briggs & Stratton with no ill effects.
Can't say about the carbon deposits but I would ask the guys in Race Only. E-85