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 # Jets 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 Metering rod Metering orifice area Power tip diam Power tip area 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.