firestone, tom is right work your up on the tune he's been doing it for a long time and know's his chit. i can give you some examples from yrs of dynoing but in no way is it to be use as every engine does the same thing. my 555 in my chevelle has 850ish hp with 38deg of timing and with 30 deg of timing it made 730hp. the engine in the duster is a 410cid and it made 500hp with 37deg of timing and 420hp with 30deg of timing. but here is the big differents the engine in the mustang was a 420cid sbc with 34deg of timing it made 900+ and with 30deg of timing it made 690hp.