Depends on the particular engine, it's state of tune, air temperature
and atmospheric pressure, grade of fuel, etc, etc. In short there's no
way to tell without trying it, and there's not really any good way to
know how high you can go before something breaks and when it does break
it's often catastrophic. Everything will be just dandy, then in a blink
of an eye you have con rods knocking holes in the engine block and oily
metal bits puking all over the road. Be careful.