For the Pontiac Enthusiast as if you didnt already know :)

Robin Ziel-Vernon — Tue, 24 Mar 2009 12:00:00 GMT

Pontiac used the same codes on different year blocks.To differentiate them it will have to be determined what year the block is.Next to the distributor hole there is a casting number that has a letter with 2 or 3 numbers. The letter is the month of manufacture- A=Jan. B=Feb,etc.

The next number or two is the day, but sometimes the factory left the first part off, i.e. 5 could mean 5,15,25.The most important is the last number,it is the year of Manufacture it is not always the model year,as most blocks are cast a few months before the car is made. In addition 1966 and earlier blocks had 2 freeze plugs on each side of the block. 1967 and newer had 3 freeze plugs per side.

These blocks had 2 motor mount holes per side.Starting in 1970, most blocks were cast with 5 motor mount holes with the mounts using 2 bolts in line with 1 higher up in the middle.Some 1977 and later blocks only had 3 holes that used the newer mounts. This means you can put a 455 in about any Pontiac car with that car's motor mounts, but if you want to use a 428 block in your 1970- Firebird you'll have to modify the frame mounts or make an adapter.

Starting around 1969 Pontiac cast a 2 digit year number next to the distributor also. They also cast the engine size on the sides of the block,usually in front of the motor mounts or between the freeze plugs.

Around 1968 Pontiac also stamped the VIN numbers next to the timing cover about even with the timing marks on cover.These are usually covered with oil and crud, and probably hard to see.This will tell you if this is an original motor.

Pontiac Engine Codes

Bold Type is for manual transmissionStarting in '73,2nd HP # is for Dual Exhaust

1964	326	250 HP	92x,96-0
	326	280 HP	94x,97-0
	389	230 HP	04L,05L,08R,09R
	389	235 HP	22B
	389	267 HP	11H,12H
	389	283 HP	10A
	389	303 HP	25K,26K,27P,28P
	389	306	23B,29N
	389	325	78X,79J
	389	330	32B,34N,33-6
	389	348	76X,77J
	421	320	35B,38S,43N
	421	350	44B,47S,49N
1965	326	250	WP,ZN
	326	285	WR,YP
	389	256	WA,WB,YA,YB
	389	290	WC,YC,YD
	389	325	YE,YF
	389	333	WE
	389	335	WT,YS
	389	338	WF,YG
	389	360	WS,YR
	421	338 HP	WG,YH
	421	356	WH,YJ
	421	376	WJ,YK
1966	326	250	WP,WX,YN,XF
	326	285	WR,YP,XG
	389	256	WA,WB,YA
	389	290	WC,YV,YU,YC,YD
	389	325	YX,YL,YW,YF,YE
	389	333	WE
	389	335	WW,WT,YS,XE
	389	360	WV,WS,XS,YR
1967	326	250 HP	WP,WX,WC,WH
	326	250 HP	YO,YN,XF,YJ,XI
	326	285 HP	WR,XR,WK,WD
	326	285 HP	YP,XG,YM,XO
	400	255 HP	XL,XM
	400	260 HP	XB
	400	265 HP	WA,WB
	400	265 HP	YA,YB,YC,YD
	400	290 HP	XV,XU
	400	293 HP	XC
	400	325 HP	WU,WZ,WQ,WI
	400	325 HP	YE,YF,YT,XE,XN,XW,XX
	400	333 HP	WD,WE,WY,XT
	400	335 HP	WT,WW,YS
	400	350 HP	XZ,XY,XH,XJ
	400	360 HP	WS,WV,WR,XS,YZ,XP
	428	360 HP	WG,Y2,YY
	428	376 HP	WJ,XK,Y3,YH,Yk
1968	350	265 HP	WD,WC,YN,YJ
	350	320 HP	WR,WK,YP,YM
	400	265 HP	XM,YA
	400	290 HP	WA,WB,YC
	400	330 HP	YT,YW
	400	335 HP	WQ,WZ,WI,XN
	400	340 HP	WU,XT
	400	350 HP	XZ,XH,YS,YZ
	400	360 HP	WT,WS,XS,XP
	400	366 HP	WY,XW
	428	375 HP	WG,YH
	428	390 HP	WJ,YK
1969	350	265 HP	WC,WP,WM,WU
	350	265 HP	XL,YJ,XR,YN,XB,YE,YU,XS
	350	325 HP	WK,WN,XC,XD
	350	330 HP	WR,WV,XT,XU,YP
	400	265 HP	XM,YZ,XX,YB,YF
	400	290 HP	WA,WB,WD,WE,YC,YD
	400	330 HP	WZ,YT
	400	335 HP	WQ,YW
	400	340 HP	XZ
	400	345 HP	WH,XN
	400	350 HP	WT,WX,YS,XH
	400	366 HP	WS,YZ
	400	370 HP	WW,XP
	400	375 HP	WI,WY,XY,XW
	428	360 HP	WG,YL,YH,XE,XJ
	428	370 HP	WF,XF
	428	390 HP	WJ,WL,YK,XG
1970	350	255 HP	W7,WU,X7,YU
	400	265 HP	XX,YB
	400	290 HP	WE,YD
	400	330 HP	XZ,XV
	400	350 HP	WX,WT,XH,YS
	400	366	WS,YZ
	400	370	WW,WH,XP,XN
	455	360 HP	WA,YC,YH
	455	370 HP	WG,XF
1971	350	250 HP	WR,WU,WN,WP
	350	250 HP	XR,YU,YN,YP
	400	265 HP	WS,WX,XX,YX
	400	300 HP	WK,WT,YS
	455	280 HP	WG,YG
	455	325 HP	WJ,YC
	455	335 HP	WL,WC,YE
1972	350	160 HP	WR,YU,YV,YR
	400	200 HP	YX,YZ,ZR,ZV,ZX
	400	250 HP	WK,WS,YS,YT,ZS
	455	185	YH,YW
	455	200 HP	ZH
	455	220 HP	YA,YC,Y4
	455	250	YD,YK
	455	300	WD,WM,YB,YE
1973	350	150,175 HP	XR,WV,ZB,ZD
	350	150,175 HP	Y2,Y7,YR,YV,ZR,ZV
	350	150,175 HP	WA,WC,WD,WF,WL,WN,XZ
	400	170,185 HP	W5,XH,XI,X3,X4
	400	170,185 HP	YI,YP,YX,YZ,Y4,ZK,ZX
	400	200,230 HP	WK,WS,WP,YN,YX,YT
	400	200,230 HP	Y3,ZN,ZS,XK,XN,XX
	400	200,230 HP	XZ,X5,YF,YG,Y6
	455	215,250 HP	WT,WW,ZZ,ZE,YA,YC
	455	215,250 HP	YD,YK,ZA,AC,XA,XE,XJ
	455	215,250 HP	XL,XY,XT,X7,XO,YE
	455	290	ZJ,XD
	455	310	Z8,X8
1974	350	155,170 HP	WA,WB,AA,YA,ZA
	350	155,170 HP	YB,YC,ZB,YN,YP,YS
	350	170,200 HP	WN,WP,ZP,YN,YP,YS
	400	175,190 HP	AH,YH,YJ,ZH,ZJ
	400	175,190 HP	AD,YF,YK,ZD,ZK
	400	200,225 HP	WT,WR,Y3,AT,YT
	400	200,225 HP	YZ,ZT,AD,YL,YM,ZS
	455	215,250 HP	AU,YR,YU,YW,YX
	455	215,250 HP	YY,ZU,ZW,ZX,A4
	455	215,250 HP	Y4,Y6,Y9,Z4,Z6
	455	290 HP	W8,Y8
1975	350	155 HP	YB,YA
	350	175 HP	WN,YN,ZP
	400	170 HP	YH
	400	185 HP	WT,YS,YT,ZT,YM
	455	200 HP	WX,YU,ZU,ZW
1976	350	160 HP (Early)	YB,YA,YP,YR,ZX
	350	160 HP (Late)	XM,XP,XU,XR,XW,XX,X3,ZF,ZH
	350	165 HP	ZX,ZF
	400	170 HP (Early)	YJ,YC
	400	170 HP (Late)	X9,X4,XT,XY,XS,XZ,X8
	400	185 HP (Early)	WT,Y6,Y7,YS,YT,YY,YZ,ZA,ZK
	400	185 HP (Late)	WY,X7,ZJ,ZL,X6
	455	200 HP	WX,Y3,Y4,Z3,Z4,Y8,ZB
1977	301	135 HP	WB,YW,YX,YH,YK
	350	170 HP	YA,YB,XB,XC,Y9
	400	180 HP	XH,XJ,XD,XF
	400	180 HP	YU,Y4,XA,Y7,XK
	400	200 HP	WA,Y6
1978	301	140 HP	XA,XC,XL,YM
	301	140 HP	XD,XB,YL,YP
	301	150 HP	XF,XH,XU,XW
	400	180 HP	XJ,XK,X9,YK,YH,YS
	400	180 HP	YT,YJ,YR,YW,YA,YU
	400	220 HP	WC,X7
1979	301	135 HP	PX7,PX9,PXF
	301	135 HP	PXH,PXP,PXR
	301	150 HP	PWA,PWB
	301	150 HP	PX4,PX6,PXL,PXN
	301	150 HP	PXS,PXT,PXU,PXW
	400	220 HP	PWH,LAST 400

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For the Pontiac Enthusiast as if you didnt already know :)

Pontiac Engine Codes