The noise of OHV generator is from valve train and other parts, and very little from the silencer, I have practically opened the silencer and the sound of generator increased, so the muffler is doing its job well. Now what about car mufflers, yes it will reduce sound but for better sound reduction the car muffler has more passages for sound to pass through like from one chamber to the other. That requires the pressure of exhaust gases to be a lot more than the generator mere small OHV running at around 3000 rpms. So if you attach a car muffler the chances are that your generator may overheat because of less exhaust gases escaping for the generator. So I think you need to live with the sound
