I put a 3 inch summit system on my old 69 coronet.It had a 499 in it and it was very loud.So i tired to switch the mufflers to some turbo mufflers,it was still loud.Then i put an h pipe on it and some edelbrock mufflers(23 inch long ones)and it was very quiet.Almost too quiet.When i sold the car i put a mild 440 in it and you almost couldnt even hear it running,lol