Assuming your car still has the Q-jet originally installed by GM, these are the specsfrom RP bulletin 9C- 14001)
Carb. model #17080207
Primary jets - #7031971, stamped "71" on jet, diameter of orifice - .071"
Primary rods - #17057742, marked "42_" on the rod, diameter at first step - .042"
Secondary rods - #7045779 - marked "CH". The tip of the rod is .0567" diameter, which is a median diameter relative to the originally available Q-jet secondary rods. The tip length is short, which is best for economy as they require a lot (> 90 degrees) of air valve opening before the rod is raised enough to expose the tip.
Do you need to change anything? Lets compare the jet sizes to what was used in a '73 L-82 (hi-per, no cats same cam). From RP bulletin 9C-3072:
Primary jets - "74's"
Primary rods - "44's"
Secondary rods - "DA's", Medium length tip, tip diameter -.0440"
Without displaying all the math, the primaries on the '73 carb are 8% richer, and the secondaries are 16% larger.
So what would I do? Start by leaving the primaries alone, but change the secondary rods. The secondary rods can be changed without disassembling the carb. I believe secondary rods can be purchased from Jeg's, Summit, etc. and/or some shops that specialize in Q-Jet performance (can be found thru Google). The only reason I would play with the primaries would be an obvious off-idle stumble or a low rpm "flat spot".
Good luck,
Mike
