[Skidmark]

For the kind of Pontiacs I have auto qjets end in an even number while the stick carbs end with odd numbers.

My question is what is the difference in performance? Are the even and odd numbered quadrajets different. If so how? Thanks

[Andre]

i don't know the exact answer, but I suspect that since we can't get the gas that was used in the 60's, the slight difference in the carbs is lost to the ages

[JSuchma]

Vacuum port for the automatic transmission modulator.

[mgarblik]

I am sure someone like Cliff could provide a very detailed answer, but a few generic differences would be: 1. Auto trans carbs typically have a few additional vacuum ports in the base plate or main body for things like the vacuum modulator and such. 2. Auto trans carbs often have a hot idle compensator for cleaner idle in drive in hot weather driving. Not aware of manual trans carbs having this feature. 3. In general, an auto trans carburetor needs an idle circuit tuned to allow smooth operation under light load from being in a drive gear with torque converter load. I am sure there are other subtle differences.

[KS circutguy]

I was under the impression they are the same.

[77 TRASHCAN]

Don't some of those stick Q-Jets lack the linkage arm for the TH350 kick down cable hook up?

[Half-Inch Stud]

I think some stick Q-JETs (68-69) have bleed holes in strange places: csn be the Pri throttle plates, or nearly parallel with the throttle shaft.

[carbking]

As a general rule (not just Q-Jets), carburetors designed for use with auto transmission vehicles are calibrated about a half a size richer than those designed for standard transmissions. The extra fuel is necessary for the additional power loss in the torque converter.

We tell folks a carb designed for an automatic may be used on a vehicle with a stick with a few percent loss in fuel economy; but using a stick carb on an automatic will generally require mild calibration changes.

Also, the vacuum port differences mentioned by others in this thread.

Jon