I have a ZZ4 350 with 10:1 compression. What is the minimum octane I can put in to not get detonation without messign with the timing or anything else?    Thanks-James  

10 to 1 is pretty out there for todays 92/93 octane premium. To a large extent how much compression you can get away with will depend upon the cam, ignition timing, operating temperature and fuel/air mixture ratio. A long cam with lots of overlap will allow more compression. The ignition timing, both total amount and or advance rate, can be backed off if detonation is a persistant problem and or the engine's operating temperature reduced or the mixture richened. 

Vehicle weight, gearing, and where you live in terms of altitude topography, and weather all have an effect. More weight, high gear ratios like 3.08 versus 3.50, hills and mountains versus flat, low altitude versus high all require more octane to supress detonation. Weather is a big problem; hot runs operating temps up which tends to detonation, but cool increases air density which can also increase detionation tendencies, depends on whether the engine is more sensitive to cooling or mixture density.

The ZZ4 has an aluminum head which helps reduce combustion chamber temperature, this builds some more compression tolerance vis-a-vis cast iron. But when all is said and dune 9.3 to 9.5 is a safer bet.

Of course if this thing is racing, then you can use high octane racing fuel, but this stuff is expensive and not always convienient to get so using it in a street vehicle is not a good choice. Octane additives are rather expensive and usually don't offer a sufficient boost to the octane rating of the fuel to make them worth while.

Bogie