i checked a c\r calulator on c-speedracing.com, and 12.5 comp. pistons in a b20 vtec with a b16 or type r head on it has an overall comp. ratio of 11.6:1. would i possibly be able run on 91 octane safe tuned with my jun III cams. because big cams drop c/r. but i dont kno how much.

 

nobody knows?

 

You'll likely get by with that fuel. Is that the best available at the pump there? You need to locate the ABDC spec on those cams and run it through a dynamic c/r calculator. There is one located here:

http://www.rbracing-rsr.com/comprAdvHD.htm