Part numbering
| 1965 through 1974 Quadrajet ID | 1975 and later Quadrajet ID |
| Example 7042283 | Example 17057282 |
| 70 = 1966 through 1975 | 170 = 1976 and later |
| 7042243 (third digit) | 17057282 (fourth digit) |
| 2 = 1966 thru 1969 | 5 = 1975 thru 1979 |
| 3 = 1966 thru 1969 California only | 8 = 1980s |
| 4 = 1970 thru 1975 | |
| 7042283 (fourth digit) | 17057282 (fifth digit) |
| 6 = 1966 | 5 = 1975 |
| 7 = 1967 | 6 = 1976 |
| 8 = 1968 | 7 = 1977 |
| 9 = 1969 | 8 = 1978 |
| 0 = 1970 | 9 = 1979 |
| 1 = 1971 | 0 = 1980 |
| 2 = 1972 | 1 = 1981 |
| 3 = 1973 | 2 = 1982 |
| 4 = 1974 | 3 = 1983 |
| 5 = 1975 | 4 = 1984 |
| 7042283 (fifth digit) | 17057282 (sixth digit) |
| 2 = four-barrel, Q-Jet | 2 = four-barrel, Q-Jet |
| 5 = four-barrel Q-Jet California only | 5 = four-barrel Q-Jet California only |
| 7042283 (sixth digit) | 17057282 seventh digit) |
| 0 = Chevrolet | 0 = Chevrolet |
| 1 = Chevrolet | 1 = Chevrolet |
| 3 = Chevrolet | 3 = Chevrolet |
| 4 = Buick | 4 = Buick |
| 5 = Oldsmobile | 5 = Oldsmobile |
| 6 = Pontiac | 6 = Pontiac |
| 7 = Pontiac | 7 = Pontiac |
| 8 = Holden | 8 = Holden |
| 7042283 seventh digit) | 17057282 (eighth digit) |
| 0,2,4,6,8 (even #’s) – Automatic | 0,2,4,6,8 (even #’s) – Automatic |
| 1,3,5,7,9 (odd #’s) – Manual | 1,3,5,7,9 (odd #’s) – Manual |
Date Codes
Example: 3283 = 328th day of 1973, ie. 24th November 1973
Metering Rods & Jet Sizes
| Primaries | Secondaries | |||
| GMH Part # | Jets | Metering rods | Metering rod | |
| HQ engines – pre ADR 27 | ||||
| 350 manual | 7041853 | 76 | 45 | AN |
| 350 THM400 | 7041854 | 76 | 44 | AN |
| 308 manual | 7041851 | 77 | 49 | |
| 308 trimatic – REF. | 7041852 | 71 | 47 | |
| HQ engines – ADR 27 | ||||
| 350 manual | Nothing listed in parts book – assume no manual cars with ADR 27 engine | |||
| 350 THM400 | 7046589 | 74 | 45 | DA |
| 308 manual – REF. | 17050641 | 77 | 50 | |
| 308 trimatic | 17050642 | 76 | 45 | |
Metering area difference compared to a HG 350 manual with Quadrajet
| GMH Carb Part # | Primary Jets |
Primary Metering rods |
Part throttle metering area | Final WOT metering area | Part throttle metering difference over HG 350 manual | Final WOT metering increase over HG350 manual | Secondary Metering rod |
Secondary Metering orifice area |
Secondary Power tip diam |
Secondary Power tip area |
Secondary WOT area |
Final WOT metering difference to over HG 350 manual | |
| HG engines | |||||||||||||
| 350 manual – refernce | 71 | 42 | 0.00257 | 0.00343 | 0.0% | 0.0% | AN | 0.01431 | 0.07000 | 0.00385 | 0.01047 | 0.0% | |
| 350 powerglide | 71 | 44 | 0.00244 | 0.00343 | -5.2% | 0.0% | AN | 0.01431 | 0.07000 | 0.00385 | 0.01047 | 0.0% | |
| 308 manual | |||||||||||||
| 308 trimatic | |||||||||||||
| HQ engines – pre ADR 27 | |||||||||||||
| 350 manual | 7041853 | 76 | 45 | 0.00295 | 0.00401 | 14.5% | 16.8% | AN | 0.01431 | 0.07000 | 0.00385 | 0.01047 | 0.0% |
| 350 THM400 | 7041854 | 76 | 44 | 0.00302 | 0.00401 | 17.2% | 16.8% | AN | 0.01431 | 0.07000 | 0.00385 | 0.01047 | 0.0% |
| 308 manual | 7041851 | 77 | 49 | 0.00277 | 0.00413 | 7.7% | 20.3% | ||||||
| 308 trimatic | 7041852 | 71 | 47 | 0.00222 | 0.00343 | -13.6% | 0.0% | ||||||
| HQ engines – ADR 27 | |||||||||||||
| 350 manual | DA | 0.01431 | 0.04430 | 0.00154 | 0.01277 | 22.0% | |||||||
| 350 THM400 | 7046589 | 74 | 45 | 0.00271 | 0.00377 | 5.3% | 10.0% | DA | 0.01431 | 0.04430 | 0.00154 | 0.01277 | 22.0% |
| 308 manual | 17050641 | 77 | 50 | 0.00269 | 0.00413 | 4.6% | 20.3% | ||||||
| 308 trimatic | 17050642 | 76 | 45 | 0.00295 | 0.00401 | 14.5% | 16.8% |
The HT and HG 350 manual engines would seem to have provided the best combination of power AND fuel economy for Quadrajet-equipped cars. All HQ 308 manual cars and all 350 cars had jets and metering rod combinations that pushed more fuel into the engine for less power out compared to the HG 350 manual. QJets on HQ 308 Trimatic cars had the most miserly part throttle primary jetting of all QJet cars.