Take it from me. The Sr20VE will take allot of detonation NA :offended: Don't ask me how I know. That makes these NA engines great for tuning experiments
irate:.
Anyway glad you got it sorted!
Just an fyi, richer mixture is not always less prone to detonation. It is a rule of thumb that VERY rich is going to cool the charge and help prevent detonation. Just as VERY lean will cause for less heat and therefore less detonation.
It is likely richening your mixture caused you to be slightly richer then stoichiometric. You had essentially tuned for peak flame temperature which occurs in the 13's depending on the octane and a few other variables. This will lead to more knock tendency VS. a stoichiometric (14.7) burn. Coupled with whatever your timing was, could have caused for noticeably large amounts of detonation. Of course this is all blabber here since we do not know your afr's. Just wanted to give you an idea of why the "richer" mixture could have excited more detonation.
This tells me you should work to verify your base timing so you can move forward knowing what your actual timing is. I guess investigate a spun pully, and verify with your timing light. Then get back to tuning!
Walker