Reboring my car engine?

i have plans on reboring my car engine (oversized), but afraid that it might cause detonation in my engine due to high compression. how can i make it a low compression engine? i have no source finding a compression tester, that's why i keep doubting whether or not to rebore my engine. what other key factors that i should consider before reboring my engine? for now its just .010 but i'm going to make it to 0.020... will i gain HP and speed? i'm doing this for a project... i'm finding ways how to make a 1.5 litre engine fast without spending too much money. thanks!