the "instructions" that came with my narrow lda 509 said put it in straight up (108). i put it at 107.5. it's in a 3350# scamp, 496, 10.33:1, 4200 stall. the thing has huge power everywhere, and, yeah. it sounds bad ass! i couldn't be happier. btw, it runs 7.0 at a slow track on drag radials!