The power increase depends entirely what spec your engine is. Just dropping in a set of pistons with the rest of the engine stock, you'll get about 3-4hp peak but bags more midrange. When you add cams and head work/bigger valves, then power starts to go thru the roof. There are a lot of 700 dyno charts on my site, just click on the banner below.
The compression ratio works out to slightly less than 11:1. Stock is about 9:1. The heads can be skimmed .020" to .040" to bump it up higher if you want. My personal Hawk is close to 13:1.
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