GMH Engine Numbers

The are several numbers stamped or cast on a block that identify the capacity of the motor and the vehicle it was installed in.
(see more information on Chevy Small Block V8 Engine Identification here)

Engine Numbers

Prefix: This refers to the identification of the engine. For a variety of reasons, engines need to be correctly identified, and it is this prefix which clarifies areas such as capacity, compression ratio, transmission, etc. The location of the engine number prefix varies depending on the type of engine.

• On all L6 (in-line 6 cylinder) engines, the prefix can be found stamped on a pad on the right (viewed from the rear) side of the engine block above the engine mount
  boss.
• On 307, 327 and 350 cubic inch VB engines, it is located on a pad in front of the right (viewed from the rear) side cylinder head on the block.
• On 253, 308, 4.2 litre and 5.0 litre VB engines, the prefix is stamped on a pad above the engine mounting on the left (viewed from the rear) side of the block.

Block: Each engine block has a casting number integral with metal castings for identification purposes. The block casting number can tell you important things likestandard bore diameter & stroke length, performance characteristics, and in the case of a Chevrolet V8 block, the crankshaft journal size and very often but not always the type of main bearing caps (ie two or four bolt).

• On all L6 engines, the casting number is located on the left (viewed from the rear) side of the block, just forward of the engine mounting boss
• On all 307,327 and 350 cubic inch engines, it is located on the left (viewed from the rear) top rear surface of the block near the bell housing attachment.
• On 253, 308, 4.2 litre and 5.0 litre V8 engines it is located on the left (viewed from the rear) side of the block slightly above and forward of the starter motor mounting pad.

Head:

• All L6 cylinder heads can be identified with the engine complete. The casting number is to be found on the top left (viewed from the rear) side toward the front of the engine. A locationg ear on the rocker cover gasket will need to be removed to expose the full casting number.
• All V8 engines require the rocker covers to be removed to expose the number.

Abbreviations: Most of these require no further explanation, however lu=limited use
and uu=uncertain usage do. These terms are limited to the HK, HT, HG and HQ models.

The rules of Series Production racing in the 1960s demanded that vehicles
involved in this motor sport had to compete in showroom stock condition. This was the
sale reason why Model Number 81837 was created. This vehicle enabled GMH to
successfully compete in motor sport despite the parent company world-wide ban on
motor sport involvement

lu=limited use - means exactly what it says. Certain parts used in the manufacture of cars were available 'officially' for very short periods of time. This satisfied the rules and as a result, these effectively 'modified' vehicles were eligible for competition.

uu=uncertain usage - is a term used where no one, not even GMH can completely clarify the correct usage of these parts, Vehicles exist in original condition with these variations, and documentation exists to support this, sometimes only in very sketchy form.

HK engines

*HK with optional 186S 2bbl. carb

HT engines

*HT with optional 186S 2bbl. carb

HG engines

*HG with optional 186S 2bbl. carb

HQ-WB engines

HQ series 1971-1974

Engine Serial Number Stamping Location
L6 - On Pad above Engine Mounting Bosses RH side of engine.
V8 - 253 & 308 cu. in - On Pad at top front LH side of Cylinder Case.
V8 - 350 cu. in. - On Pad RH side top surface of Cylinder Case, front of Cylinder Head

Engine Identification and Specifications

Note: The Statesman Engines carry an additional prefix of "11" preceeding the Alphabetical Prefix

HJ series 1974-1976

Note: The Statesman Engines carry an additional prefix of "11" preceeding the Alphabetical Prefix

HX series 1976-1977

HZ series 1977-1980

WB statesman deville & caprice 1980

BLOCK CASTING NUMBERS

You can actually find the exact day on which that engine was cast by finding the date code on the engine block.

This will be located on the very top front of the engine block near where the water pump bolts on (just forward of the front edge of the inlet manifold). Just behind the top of the timing casing/water pump.

It will be a 3 or 4 digit code consisting of several numbers and at least one letter. There will also be a little clock symbol just near it. This clock actually signifies the exact time of day that the block was cast.

Casting dates are very simple to decode

The first on or two letters are the day of the month.

The letter is the month
A = Jan
B = Feb
C = Mar
D = Apr
E = May
F = Jun
G = July
H = Aug
J = Sep
K = Oct
L = Nov
M = Dec

(I is not used so H=Aug then J=Sep)

The last number is the year. 2=72, 3=72 etc

Earlier blocks (which have a different prefix on the engine number [253H]) will have the month before the day in the date code. Later blocks such as 82, 83 etc can be distinguised from 72, 73 by having 4.2 cast on the side instead of 253. There are also other differences as well but that is a very simple one.

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