In 1987 I switched from the purple shaft hydralic .455 RV cam with a Holley 650 vac. sec. to that .509/292 purple cam in my 1969 300 440 big block, with factory oem compression(10 to 1) and stock 906 heads (except for a fresh valve job with stock valves). And the Holley 750 #3310 carb. It made a HUGE NIGHT AND DAY DIFFERENCE in performance! I had power brakes, which worked fine with that .509 and it idled around 800 RPM or so in gear. That big car could do tremendous burnouts, AND keep up with new Buick Grand Nationals on the street !