How would I convert 179cc to horsepower?

You can't. It is like saying "how do I convert gallons into dollars". What you need to answer to do the conversion is "gallons of what?" What sort of engine do you have? ...2 stroke ...4 stroke? Since a typical 4 stroke fires half as often as a 2 stroke at the same RPM, the 2 stroke will put out approximately twice as much horsepower. Then, you have to state what RPM you are testing at. That said, a 179 cc 2 stroke motor could be expected to put out somewhere around 10 brake horsepower. Your mileage will vary.