Identifying Big Block Mopar Engines

Block Serial Number Stampings

(On B engines, 351-400 ci, there is a pad on the right front of the engine below the distributor. On RB engines, 413-440 ci, there is a pad on the left front of the engine. These pads contain stampings that will quickly identify an engine and usually tell you a little about it.)

The stampings on the top of the block will look something like this:

C H 426 B

(These particular markings are of the form:)

Series / Hemispherical / CID / Bodytype
Month-Day-The Number Engine Built This Day

These marking are noted below. The stamping on the bottom of the block will be the formal serial number for that block and read similar to the following:
9-10-68 PT38326010001. These numbers are decoded as follows:
A. The first numbers are the date of the stamping (9-10-68)
B. The next letters indicate the engine assembly plant- in the case of our example, Trenton.
C. The next three digits indicate cubic inch displacement: 383 cid.
D. The next four digits (2601) are the 10,000 day calender numbers: 2601 = Sept 10, 1968.
E. The final four numbers (0001) show that this was the first engine assembled that day.

S = 1962
T = 1963
V = 1964
A = 1965
B = 1966
C = 1967
D = 1968
E = 1969
F = 1970
G = 1971
H = 1972
J = 1973
4T = 1974
5T = 1975
6T = 1976
7T = 1977
8T = 1978

Diamond = 0.008-in. oversize tappets
Maltese Cross = 0.001-in. undersized crankshaft
Maltese Cross and an X = 0.010 undersized crankshaft
A = 0.020-in. oversized cylinder bore
B = 0.010-in. undersized main and rod bearings
E = cast crankshaft
H = standard 4bbl
HP = high performance
LC = low compression
O.S. = 0.005 oversized valve stems
P = premium fuel recommended
R = regular grade fuel may be used
S = special engine
WT or TW = water test
X = oversized valve guides

K = Toluca
PT = Trenton
M = Mound Road
T = Trenton (400 and 440 only)
MV or MN = Marysville

Note: This information comes directly from page 49 of HPBooks "How to Rebuild Big-Block Mopar Engines" by Don Taylor and is repoduced w/o their permission. This is a very high quality book full of valuable resources and numbers and I recommend it to anyone interested in these engines.