i have just put in a high compression piston with 10.25:1 compression and bought 93 octane fuel for it the person that is putting this piston in for me says that this wiseco piston reccemends 103 octane. will 93 be high enough or will i have to use an additive. People also talk about pinging what is that and what does it sound like. ALso the difference in the way the pistons are put in don't that have a role in what octane fuel you need. Thanks for your help.

There are a few things to consider when determining what octain you should run.
Its not just the compression ratio of the piston. Other considerations are the intake air flow,(how much air the engine will pull in). The best way to tell is to do a compression test. Around 200psi, yes you should be using around 100 to 104 octain.
Other considerations air temp., altitude, timing adjustments,and other mods.
I have a very modified Wolverine, with an .080" bore, ported head, and cam, 11:1 compression. And it runs 92 oct.
Knocking is just pre-ignition.
A higher oct fuel is actually less flamable than a lower oct.
What happens is compression builds heat, sometimes enough to actually ignite the fuel prematurely, thus a knock as the piston is coming up to top dead center.
This is very bad on the piston and rod.
Hope this helps...

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Thanks for your help, but if your using 11:1 and i am only using 10:25:1 then wouldn't i get away with 93 octane fuel. Also you said that valves have something so do with it so do YOu make the cleareance more or less.