Technical Information: Pontiac 400 428 455 Engine ID

Technical Information
Pontiac 400 428 455 Engine Codes

This is a quick block ID for junk yard hunting, etc. You must find the date code at the back LH side of the block first. The letter is the month, next 2 digits are the day and the last digit is the year. Here are 2 examples:

A249 code "XE"
A = January - 24 is the 24th day - and 9 is 1969
The block is a 69 428.

Another example is:

K109 "WA"
K = October or November - 10th day - 9 = 1969
The block is a 70 455 4 bolt.
These motors usually have a large "70" at the rear of the block.

*Note - blocks with only 2 mounting holes or pads (for the motor mounts) per side is from 1969 and older blocks with 5 or 3 mounting holes or pads (for the motor mounts) per side is from 1970 and newer blocks with 2 freeze plugs per side is 1966 and older blocks with 3 freeze plugs per side is 1967 and newer certain blocks for 4 bbl carb usage have scallops in the cylinders at the deck for unshrouding the intake valves. Most 1967 and earlier blocks place these scallops at approx 4 o'clock and 8 o'clock while 1968 and newer blocks place the scallops at 3 o'clock and 6 o'clock . Early 2 bbl blocks and most newer blocks did not have any scallops.

400 Engine Codes

Year	Model	Codes
1967	GTO	XM XL WT WW YS XE WS WV YZ YI (RAM AIR) XS YR XP
1967	Firebird	WZ WU YT (RAM AIR) WQ XN WI
1967	Fullsize	XA XB WA WB WM WN YA YB YC XV YD XU YU YV XC YE XW YF XX YX WD XT WE WY XY XZ YL XH XJ WF
1968	Fullsize	YA XA WA WB YC ZR YE YF XZ XH
1968	GTO	XM WT YS (400 HO) WS YZ (RA I) XS XP (RA II) WY XW
1968	Firebird	WZ YT (400 HO) WQ YW (RA I) WI XN (RA II) WU XT
1969	Firebird	WZ YT (RA III) WQ YW (RA III) WH XN
1969	GTO	WT YS XM XX (RA III) WS YZ (RA IV) WW XP
1969	Fullsize	WA WD YA YB WB WE YC YD XZ WX XH YF WA WD YA YB WB WE YC YD
1970	Fullsize	WE YD YB XZ WX XH
1970	GTO & Firebird	XX XV WT YS (RA III) WS YZ (RA IV) WW XP
1971	Fullsize	WS XX YS
1971	GTO, GP & Firebird	XX WT WK YS
1972	All	YX YZ ZX WS WK YS YT
1973	All	YP ZK Y4 YX Y1 ZX YZ YT XK ZN WS YF WP Y6 YG YN ZS YY XX X5 Y3 YS XN
1977-79	T/A 6.6 (W72) option	casting number 481988 XX is cast on the valley area and externally

428 Engine Codes

Year Codes

1967 WG YY YH Y2 XD WJ XK YK Y3

1968 WG YH WJ YK

1969 YL YH WG XK XE XJ WJ YK WF XF WL XG

455 Engine Codes

Year Model Codes

1970 Fullsize YH - 2 BOLT WG XF - 4 BOLT

1970 GTO WA YA YC - 4 BOLT

1971 Fullsize WJ YC WG YG - 2 BOLT

1971 Others HO (4 BOLT) WL WC YE

1972 2 BOLT YH YC YA ZH

1972 4 BOLT (HO) WM YB WD YE 4 BOLT (HO) WM YB WD YE

1973 YK X7 YD XM WW WT YC XE YA XL ZC ZA (SD) ZJ XD

1974 Y9 Y4 Y6 A4 Z4 Z6 YY YU YX AU ZU ZX YW ZW YR (SD) W8 Y8

1975 YW YU ZU ZW WX

1976 Y3 Y4 Z3 Z4 Y8 ZB WX