400s are torquey motors not high HP motors, but that doesn't mean you cant boost the HP... with a rebuild you could easily get some HP by boring it, decking it a little bit, mill and port and polish the heads, add a mild cam, a better intake and a 4bbl carb... those 76cc heads alone kill a lotta power... if you mill the heads right you can cut down the combustion chamber size and raise compression to a little tastier amount....