R/A III Carb question
 

Hey guys. Gotta question concerning carbs. On my 70 Judge (R/A III) I noticed I did not have the right carb #7040273. The carb was off a 70's Firebird. So I sold it and later bought a 70 GTO carb #7040262 that was on a 455. It is a 750 cfm. I do have the #'s matching cam,intake, and heads. I know the 7040262 is for a auto tranny and I do have a 4speed car. If the are both 750 cfm's what are the differences in the 2 performance wise? If I were to run the 7040262 for a while then switched to a 7040273 would there be a great deal of improvement? If so what would it take to make the 7040262 perform like the 7040273? Thanks

ALL 1970 RamAir M/T engines used the #7040273 Quadrajet, and so did your 1970 Judge.

#7040262 were used on 1970 Bonneville, no GTO used this Q-jet.

Both are 750cfm, but the 273 is much richer calibrated from idle tubes, idle channel restrictions, off-idle slots, main jetting and secondary emulsion tubes.
Also the 262 is more emission oriented using the primary POE-system for using leaner part-throttle jetting.

With all that said, both can be equal in performance once properly adjusted/modified in areas described above.

What carb # did the standard 350 HP GTO 400 come with?

#7040263 for M/T and #7040264 for A/T.

^^Thanks!^^

One minor addition. For MT RA III/IV cars built in California, the carb was 7040573. 7040570 for AT CA RA cars.

my preference goes to the 7040262 about 5:1 in favor of the Off-idle pull & 60 foot capability. It's the top-plate, and seemingly easy to dial that sort of carb in.