Compression - How much is too much?

[ZDoman]

I used to do my engines around CR 11:1 if I removed the "joggles" inside the combustion chamber. Running on 98octane petrol. Without any problems by this time.
If you don't remove the joggles I think around 10,3-10,5 is the safe.

I always used to resurface the cyl head and the block top. Especially the block top used to have some small "rust" points, it used to be -0,1-0,2mm off the top to get it OK. With this I wasn't able to use thin metal headgasket on any of my engine (i tried 0,8mm) because the piston was knocking on the cyl head at the first engine start. So be careful!

I know an AW11 guy who has 12:1 CR with stock everything and he rallycross race the car. He told its not revving over 7000 but has a great torque I wouldn't try it, but it is working for a long time for him...maybe 99+ octane petrol, I don't know.