RCING1, thanks for the tip. Great site, with loads of info. Too bad there is nothing on the ryobi. The port timing figures in the "hot rod" section look a little too stout for a slow reving Ryobi. Think that I'll try to "sneak up" on the 160 deg exh. figure, a little at a time, & check the results about every 5 degrees. Thanks again. ....... Geo.K.