here is a vid of my 366 RA V NASCAR engine in 69 bird.1K RPMs,2 1/2 with H pipe and Hushpower mufflers.Have them on my 421 63 Lemans also.They are small and much quieter than the flomaster I replaced.No issue listing to my radio and no drone like the flos.Love them.Tom
https://www.youtube.com/watch?v=HSmu7-0WkAA