I dont think it would be worth the risk. (though i did it, "do as i say not as i do" i guess
) There is a tool out there (perhaps called valve relief cutter or somthing) which is pretty much a valve with cutting blades on it, you just attach to a drill and push it into the piston. Again, this is something I havent done (it seems like things are getting more and more like that...) so dont go to town with my advice, wait till the others whom have rebuilt more than one engine help ya out. Best of luck.