70-81 ENGINES CODES
Identify a PONTIAC engine block is very simple, the code is entered, or rather "hit" on the front right of the cylinder block (when you're driving), close to the plane of the cylinder head gasket. Often it isn't visible at first sight either because it may be hidden by rust, paint or air conditioning compressor support. You will find a set of a pair of letters designating the engine code and number that is the serial number of the engine.
Below you will find the 180 codes for engines installed in firebird. Generally we can see that PONTIAC for blocks codes beginning with "W" for engines with manual transmission and codes beginning with "Y" for engines with automatic transmission, this for the V8 engine.
The color codes in the table below are made to differentiate the four brands of engine fitted to the firebird.
PONTIAC CHEVROLET BUICK OLDSMOBILE
1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 A3 400 AA 350 AD 400 AH 400 AT 400 AU 455 265 AW 265 AZ 265 BA 265 BD 301 BJ 301 BO 301 CAA 250 CAB 250 CBA 250 CBG 250 CBJ 250 CC 250 CCA 250 CCB 250 CCC 250 CCD 250 CD 250 CEL 305 CEM 305 CF 250 CH 250 CJ 250 301 CL 250 CSD 250 D6A 305 D6B 305 D6C 305 D6D 305 DB 265 DC 265 DH 265 DHA 305 DHB 305 DHC 305 DHD 305 DHF 305 DHH 305 DHJ 305 DHK 305 DHU 305 DHZ 305 DJ 305 DKB 305 DND 305 DNF 305 DNJ 305 DNK 305 DNZ 305 DRY 350 EA 231 EC 231 EE 231 HF 350 HJ 350 HL 350 HR 350 JL 250 JT 250 JU 250 LZ 231 MS 231 MX 231 NA 231 NB 231 NC 231 ND 231 NF 231 NJ 231 NK 231 NL 231 231 NZ 231 OJ 231 OK 231 OL 231 OM 231 ON 231 OZ 231 Q6 403 Q8 350 Q9 350 QE 403 QJ 403 QK 403 QL 403 RA 231 RB 231 RC 231 RD 231 RK 231 RL 231 RX 231 RY 231 SG 231 SI 231 SK 231 SM 231 ST 231 SU 231 TD 403 TE 403 TH 305 TJ 305 TK 305 TX 350 TY 350 U2 403 403 U3 403 403 VA 403 403 VB 403 403 W8 455 455 WA 350 400 WB 301 WC 455 400 WD 455 WH 400 400 WJ 455 WK 400 400 400 WL 455 WM 455 WN 350 350 WP 350 400 WR 350 350 WS 400 400 400 WT 400 400 455 400 400 400 WU 350 350 400 WW 400 455 WX 455 455 X4 301 X6 301 X7 400 XA 400 XC 301 XM 301 XN 400 400 301 XP 400 301 XR 350 350 301 265 XX 400 400 Y3 400 400 Y6 400 400 Y8 455 455 Y9 400 350 YA 455 350 400 YB 455 350 350 YC 455 455 YD 455 YE 455 455 YF 400 YG 400 400 YH 400 301 YK 455 301 YL 350 400 301 YM 400 YN 350 350 301 YO 350 YP 350 YR 350 350 350 YS 400 400 400 400 400 400 YT 400 400 YU 350 350 350 400 YW 455 YX 400 400 400 YY 455 YZ 400 400 400 400 ZA 350 ZB 250 ZF 350 ZG 250 ZJ 400 ZK 400 400 400 ZP 350 ZR 350 ZS 400 400 ZT 400 ZX 400 400 350 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981
There is another code that is located along the lid and timing cover. It should be the end of the VIN code of the car (the panel). If it doesn't match, engine is not from the factory.
In 1970, all blocks received three additional holes (5 in total per side) for the installation of engines in the new pontiac firebird chassis of the second generation. Below the serial numbers had to be sure to identify the engine size. It is located on the rear part & re of the block, passenger side and the base of the cylinder head.
1970 (350 ci) #9799916
1970 (400 ci) #9799914
1970 (400 RA III) #9799914
1970 (400 RA IV) #979991(5)
1970 (400 RA V) #481708
1970 (455 ci) #9799140
1971 (350 ci) #481990
1971 (400 ci) #481988
1971 (455 HO) #483677
1971 (455 HO) #485428 late
1972 (350 ci) #481990
1972 (366 ci) #(485)212
1972 (400 ci) #481988
1972 (455 ci) #485428
1973 (350 ci) #488986
1973 (400 ci) #481988
1973 (455 ci) #485428
1973 (455 SD) #(490)132
1974 (350 ci) #488986
1974 (400 ci) #481988
1974 (455 ci) #485428
1974 (455 SD) #(490)132
1975 (350 ci) #488986
1975 (400 ci) #488986 early
1975 (400 ci) #500557 late
1975 (455 ci) #500813
1976 (350 ci) #488986
1976 (400 ci) #500557
1976 (455 ci) #500813
1977 (400 ci) #568557
1978 (400 ci) #568557
1979 (400 ci) #568557
All blocks have a date code of manufacture at the foot of the distributor. It consists of a letter (A = January, B = February ... L = December) and two or three-digit day of the month, the last being the year. Example: D036 -> April 3, 1976. This is to match the casting number in the table above not to be confused with the 60s.
Unlike this time and our European cars, a Pontiac wasn't necessarily motorized by PONTIAC engine, and all displacements combined, there was also Chevrolet, Buick and Oldsmobile engines on the second generation firebird. This bio-diversity appeared in 1977.
Chevrolet V8 engine offered were only the small block 305ci (5.0L) and 350ci (5.7L), but also had to rely on the venerable six-cylinder fitted to the firebird base for almost forever. So apart from the L6, the two V8 were installed from 1977 to 1981. The 305 is 3.736"x3.48" (95x88.4 mm) bore and stroke and from 125 to 150hp depending on the year. The 350 is 4.00"x3.48" (102x88mm).
For Buick, only the V6 231ci (3.8L) versions of this base was offer. Bore 3.8"x3.85" (96.5x97.8mm). In fact we must consider this V6 as a V8 350 which it would have been cut 2 cylinders. Used from 1978 to 1981, producing from 105 to 115hp.
Oldsmobile V8 350ci (for 1977) and the famous 403ci (1977 to 1979) eventually to expand the range of the engine. The 350ci's cylinder heads were manufactured by the PMD (Pontiac Motor Division) but only from 1977 to 1980. The 403 is a special block with a bore/stroke of 4.351"x3,385" (110.5x86mm) as saying that the short stroke favors high speeds engine. But with a big bore, the wall cylinders are thin and the coolant doesn't pass between the cylinders, causing some overheating problems ... Power 185 hp (138 kW) and 320 lb-ft (433 Nm).
CYLINDER HEAD
They are as important as the engine code because often they are replaced by "good" versions, those that offer more compression and more power. 3 codes on them, for example: Type: 4X, 5C, 6X, date and combustion chamber size....
Here is a picture of one of my head to illustrate the locations of these codes and serve as an example.
1973-74, 4X heads
4X-1H, 455, 2.11/1.66" valve, press in stud, 114cc
4X-3H, 400 4bbl, 2.11/1.66" valve, screw in stud, 98cc
4X-4H, 400 2bbl, 1.96/1.66 "valve, press in stud
4X-7H, 400 4bbl, 2.11/1.66" valve, screw in stud, 98cc
46, 350 2bbl/4bbl, 1.96/1.66" valve, press in stud, 86cc
4C-5, 350 wAIR, 1.96/1.66" valve, press in stud, 86cc
4C-9, 400 wAIR, 1.96/1.66" valve, press in stud, 98cc
1975, 5C, valve length 4.960/4.949", diameter 2.11/1.66" and 30°/45° valve seat
5C-4, 350 4bbl, 93cc
5C-7, 350 4bbl AIR, 93cc
5C-8, 400 4bbl, 101cc
5C-9, 400 4bbl AIR, 101cc
The 6X heads were installed after February 1975. The 6X-4 and 6X-8 heads were used only after 1976. diameter 2.11/1.66"
6X-4, 350 (et 77-79 T/A 6.6), 93cc
6X-8, 400, 101cc
6H-6, 455, 124cc
6S-7, 350 w/AIR, 93cc
6S-9, 400 w/AIR, 101cc
The date of manufacture; HO84 here and based on the first letter designating the month (A = January, B = February, etc. ...), and the third two digits for the day (01 is the first of the month up to 31) and finally the last digit for the year (4 = 1974 5 = 1975, etc. ...). This gives H = August 08 = Day 8, 4 = 1974. So my heads were made August 8, 1974 which is normal for a car model produced in 1975 late 1974.
Combustion chamber size: 4 corresponding to the small size which is 93cc for the 5C heads.
YEAR Ci POWER HEAD CODE VALVE COMP. 1970 350 255HP 11 1.96/1.66 8.8 c.r. 400 265HP 11 1.96/1.66 8.6 c.r. 400 290HP 16 (small valves) 1.96/1.66 10 c.r. 400 330HP Big Car 16 1.96/1.66 10 c.r. 400 330HP 12 (manual) 2.11/1.77 72cc 400 330HP 13 (automatic) 2.11/1.77 72cc 400 345HP(FB/RAIII) 12 2.11/1.77 72cc 400 350HP(GP) 13 2.11/1.77 72cc 400 350HP(GTO) 12 (manual) 2.11/1.77 72cc 400 350HP(GTO) 13 (automatic) 2.11/1.77 72cc 400 366HP(GTO) 12 (RA III) 2.11/1.77 72cc 400 370HP(RA IV) 614 (round port) 2.11/1.77 71cc 455 360HP Big Car 15 1.96/1.66 87cc 455 360/370HP(GTO/GP) 64 2.11/1.77 87cc 1971 350 250HP 94 1.96/1.66 96cc 400 265HP 99 1.96/1.66 98cc 400 300HP 96 2.11/1.77 96cc 455 280HP 98 1.96/1.66 114cc 455 325HP 66 2.11/1.77 114cc 455 335HP (455HO) 197 (191) round port 2.11/1.77 111cc 1972 350 175HP 7h1 1.96/1.77 7.6cr 400 200HP 7j2 1.96/1.77 8.4cr 400 250HP 7k3 2.11/1.77 96cc 455 200HP 7L4 2.11/1.77 114cc 455 250HP 7M4 2.11/1.77 114cc 455 250HP 7M5 2.11/1.77 114cc 455 300HP(455HO) 7F6 round port 2.11/1.77 111cc 1973 350 150/175HP 46/4c 1.96/1.66 96cc 400 170/185HP 46/4c 1.96/1.66 98cc 400 200HP 4x/4c 2.11/1.66 98cc 400 230HP 4x/screw in stud 2.11/1.66 98cc 455 215/250HP 4x/screw in stud 2.11/1.66 114cc 455 290HP(455SD) 16/X (round port) 2.11/1.77 111cc 1974 350 155/170HP 46/4c 1.96/1.66 7.6cr 350 200HP(GTO) 46 (screw in stud) 1.96/1.66 7.6cr 400 175/190HP 46/4c 1.96/1.66 8.1cr 400 200HP 4x/4c 1.96/1.66 98cc 400 225HP(AT) 4x (screw in stud) 2.11/1.66 98cc 400 225HP(AT) 4c 2.11/1.66 98cc 400 225HP(MT) 4x (screw in stud) 2.11/1.66 98cc 455 215/250 4x (screw in stud) 2.11/1.66 114cc 455 215/250 4c 2.11/1.66 114cc 455 290HP(455SD) 16/X (round port) 2.11/1.77 111cc 1975 350 ALL 5c 2.11/1.66 7.6cr 400 ALL 5c/6s 2.11/1.66 7.6cr 455 AIR 6s 2.11/1.66 7.6cr 350 HO/non-air 6h 2.11/1.66 7.6cr 1976 350 ALL 6X/6S 2.11/1.66 7.6cr 400 ALL 6X/6S 2.11/1.66 7.6cr 455 AIR 6S 2.11/1.66 7.6cr 455 HO/non-air 6H 2.11/1.66 7.6cr 1977 301 ALL 01 1.72/1.50 8.2cr 350 ALL 6X/6S 2.11/1.66 7.6cr 400 180HP 6X 2.11/1.66 7.6cr 400 200HP 6X 2.11/1.66 8.0cr 1978 301 ALL 01/02 1.72/1.50 8.2cr 350 ALL 6X/6S 2.11/1.66 7.6cr 400 180HP 6X 2.11/1.66 7.6cr 400 220HP 6X 2.11/1.66 8.1cr 1979 301 ALL 01 1.72/1.50 8.2cr 400 ALL 6X 2.11/1.66 8.1cr