We DON"T KNOW your exact compression ratio, and
we DON"T KNOW your exact cylinder pressure.
If we did, we could back-estimate the severity of your problem. All we have are these;
So all AJ can tell you is that if you install a smaller cam; the engine will immediately make more cylinder pressure. And more pressure can quickly morph into detonation. Actually in your case, it might only take a few degrees less Ica, to make it undriveable at the new pressure, cuz we have NO STARTING POINT, so we are all just best-guessing.
What we can do is recommend a nice street cam, and then generate the easy compression ratio based on various input factors... like;
Your altitude
the gas you are willing to buy
what trans,TC, and gears you want to run, and what your expectations might be for the finished combo.
In your case, you already have high compression pistons, so milling the tops off is an option.Which as already mentioned, would require a rebalance, and so between those two costs, you are close to the price of new pistons; also already mentioned.
In your case, everything is connected to everything else and there is no easy/cheap solution .............
Except maybe a whiplash/ thumpr type cam,or a variable-duration lifter, or some combination.
But;
until we know where the current cylinder pressure is,
as they say,
we're just spit-balling.
