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Hemi Identification: Part I

The History and Quick Visual Identification Queues

This article is to help anyone like me who loves early Chrysler, Dodge, and Desoto hemi engines in hopes that you will find one and save it! It is a two part guide to help you identify the engine you are lucky enough to discover and give you a bit of history on what has become a legendary engine for hot rodding and racing.

Early hemi engines were born from Chrysler’s involvement in the production of military aircraft engines during World War 2. After the war they utilized the wisdom they had gained to produce a production car engine to compete with other overhead valve power plants being made available such as the early Cadillac V8, Nailhead Buicks, and Oldsmobile V8s.

It is also interesting to note how much Chrysler learned from looking at other groundbreaking designs preceding them such as Arkus Duntov’s “Ardun” overhead conversion cylinder heads for flathead fords. When you study an Ardun Cylinder head you can understand why it worked so well breathing new life into the Flathead. While it is not well documented that Chrysler was inspired by Duntov, a quick look at a set of 241 Red Ram heads from 1953 might convince you!

Another interesting thing to note about early Hemis is that each division of Chrysler worked from the same playbook, but developed their own versions of the Hemi for their specific vehicles. Because of this none of the parts from each division’s engines interchange. Dodge, Desoto, and Chrysler engines all have their own internals, features, and benefits. Each was created separately, but one thing they all share is a great attention to detail and quality of foundry and machine work. In comparison to other engines of the time period, early Hemis are known for showing great precision in machine work and accuracy with regard to symmetry and consistent wall thicknesses in block and head castings.

Chrysler made its engine available first and debuted it in 1951. Desoto would follow in 1952, and then Dodge in 1953. The run of early hemis was relatively short lived and by 1959 Chrysler would cease production in favor of cheaper to produce wedge head engines.

A quick Visual Identification- before getting into the finite details and crunching numbers you can generally identify what hemi engine you have by simply looking at it. Hemi engines get their name from the layout of the combustion chamber design. A hemispherical combustion chamber with the spark plug placement directly over the pistons meant a large cylinder head casting and impressive looking valve covers where the plugs dropped straight down the middle.

Chrysler Corporation being proud of their achievement embossed different words on the valve

Chrysler Embossed Valve Covers

Chrysler Firepower, IMPERIAL, Chrysler Marine, & Chrysler Industrial

Chrysler Firepower
Chrysler Marine
Chrysler Industrial
Dodge Valve Embossed Covers

Dodge Red Ram & Dodge Super Red Ram

Dodge Red Ram
Dodge Super Red Ram
Desoto Embossed Valve Covers

Desoto is embossed on the wire cover running down the middle of the valve cover.

Desoto FIRE DOME Eight
Desoto FIRE FLITE Eight

Extra bumps in the valve covers where the wire caps install are a sign that your engine was set up with adjustable rockers. These are desirable and were typically installed on Marine and Industrial Engines.

Chryslers are physically the largest of the early engines making them easy to spot when sitting close to their Desoto and Dodge cousins. It is also important to note that the engines were always cast in iron and increased in cubic inches over the years. In terms of weight here is the how they scale:

Casting visual ID- If you come across pieces of a Hemi there are some easy ways to Identify them visually as well.

Chrysler Blocks

331 - 354 – Notice the uppermost water pump mounting holes are very close to the top of the deck. Note early 331 engines had intergral bellhousings. These are referred to as extended bellhousing blocks and were the earliest engines. The oil pan rail also differs in the front on these early engines therefore later oil pans from 1955-1958 will not work. Note also that the bellhousings can be machined off but it requires a talented machinist. There are also transmission adaptors through Wilcap which allow various modified transmissions to be mounted to the block in its original “extended” configuration.

392 (featured a “raised” deck) – There is more space between the upper most mounting hole for the water pump (1/2 inch).

Industrial and Marine – Note the extra coolant ports. It is also important to note that Industrial and Marine engines may have come equipped with sodium filled valves. Handle these with care! Also be weary of Marine engines which may have been cooled by lake/sea water. These engines can be used for the street but require special consideration.

Chrysler Heads

331 heads do not feature a water outlet on the heads, but are otherwise interchangeable with 354 heads. Heads are not RH or LH specific and can be swapped side to side.

354 heads have water ports on both front and back. They differ from 392 heads in that if laid on a flat surface you will see the intake ports are further off of the surface in comparison to 392 heads.

392 heads are recognizable when on a flat surface because the intake ports nearly touch the surface.

Dodge Red Ram and Super Red Ram

Dodge blocks are physically the smallest of the early hemi engines and can be easily identified by the style of the valley cover and the fact that they do not have engine mount provisions on the side of the block. Cylinder heads feature water ports and can be swapped side to side.


Desoto engines are the most difficult to find speed parts for. They can be identified due to their smaller size and distinctive valve covers. They also have engine mount provisions cast into the side of the block unlike the Dodge.

There were no variations of Industrial applications for the Dodge or Desoto engines. Chrysler Industrials are well known for having been used for irrigation pumps, air raid sirens, and generators.

If a visual ID is not enough and you want to know more specifics continue to part 2 to learn exactly where to find casting and ID numbers and what they mean!

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