1980 Q-jet jetting questions

[zackm58941]

Hi, I have a 1980 4spd and I'm not sure on what jets to put in. I already have dynomax long tube headers, cat delete, dynomax ultraflow mufflers and edelbrock pro flow intake(basically stock). I am gonna be installing the L-82 camshaft and was woundering what the stock jets were on my Q-jet and what should I bump them up to? This engine (l-48) is only going to be in the car for another year and then I'm buying the GM crate engine (350HO, 330hp) but I want to get a little more out of it for the time being. I dont want to spend money on a new carb so I figured this will be the best route for now. Any input would be greatly appreciated!!!

Zack

 

[wishuwerehere82]

Hi Zack,

Frank's Garage on Rome St. off the inner loop specializes in Quadrajet rebuilds. You could probably give him a call for the jet numbers. His # is 325-6938. He may also know what a good match to your cam and headers might be. He also rebushes and rejets carbs.

Where are you in Rochester? I'm up by the lake in Greece, close to Charlotte.

Pete.

 

[MMM]

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

 

[zackm58941]

Thanks guys! I'm living in west irondequiot, its good to here from someone in the same area. I might go with MMM and try to go more along with the 73's jet sizes and see what happens, other wise I might give Frank's Garage call. It does has a little off idle stumble or flat spot as you put it so I might go with both the secondary and primary jets too. I'll post back when I order the jets and put them in, I mine as well re-build the carb while I'm in there anyways.

Thanks again,
Zack

 

[wishuwerehere82]

It would be fun to get some other members together and have a mini Vette show when the weather gets a little(lot) nicer. Fredsvettes, Stangmata, Goingballistic, and a few others live in this area.


Pete.

 

[zackm58941]

That would be cool to get some people togather for a little show. I have been in North Carolina for the past year and a half for school and the weather down here is so nice compared to rochester, its gonna be hard coming back to that, haha.

Zack

 

[wishuwerehere82]

Don't hurry home just yet, it's going to snow this weekend.

 

[bill81vette]

Don't hurry home just yet, it's going to snow this weekend.

supposed to rain on this side of the state!!!