Block ID Stamped Numbers

Motor Unit Number
The sequential production number for the engine. Often referred to in service bulletins to identify production changes or service issues. It appears all Pontiac engines were cast and machined in Pontiac, MI.

Engine Code
Two character code identifies the engine assembly. This is like an engine "model designation"  and can be cross-referenced to just about all the parts used on the engine. The same engine codes were used for vastly different engines, so one must know the year of the engine as well.

Partial VIN
Usually starting with 2P..... It identified the VIN of the particular car the engine was installed in.

Block ID Stamped Numbers (closeup)

Motor Unit Number
Note that it is a 6 digit number.
Prior years had a leading "0" for a seven digit number.

Engine Code
 2 character application code

Block ID Casting Numbers by Distributor

74  Model year

E214 Casting date E = May, 21=21st day, 4=1974

2 Foundry casting line?

D<N Cast on Day shift

Note Allen head oil galley plug is not original. Pontiac used square drive plugs

Block ID Casting Numbers Passenger Side Rear

481988  Block casting number

Circle with dots Time cast = 8am?

2 Foundry casting line?

Block ID Casting Numbers Lifter Valley
Often these numbers are missing, especially on 4 bolt main and other performance blocks.

5 / 0 = 350 block

0 / 0 = 400 block

2 / 8 = 428 block

5 / 5 = 455 block

X / X = 78-79 blocks

Block ID Casting Numbers Driver's Side

400 = 400

455 = 455

Sometimes this number may be missing

Note the 5 motor mount holes

Block ID Casting Numbers Passenger's Side

400 = 400

455 = 455

Sometimes this number may be missing

Located behind dipstick tube

Sometimes this number may be missing

Head ID Stamped Numbers 

3H = 400 4bbl 4X head with screw-in studs and heavy valve springs for manual trans car.

1974 HEI distributor

Some of you will say that HEI did not come out until 1975, but this is not true. HEI was released May 1st, 1974 which required new engine codes for the rest of the 1974 production year. Most, but not all engines got HEI. The 455SD did not.

The distributor has the number stamped on the side of the housing and also on the aluminum tag shown. 112871 is for a WR code manual trans 400.

The date code 4E17 translates to:
1974 
May (A=1, B=2, C=3, D=4, E=5...)
17th day of the month

4 different types of distributors were offered in 1974
Points
Uniset points (combined points and capacitor)
Unitized Ignition
HEI.