Early Hemi Engines

It was the design of the " Hemi " head that really stamped the

Chrysler, Dodge and Desoto engines as being different yet

unique.

The hemi headed engines were already common in Europe , mainly

Grand Prix race engines, with the valves open and shut by twin overhead

camshafts.

Chrysler decided to adopt a different approach , instead of leaving it's single

five bearing camshaft in the vee of the bent eight, they chose to run adjustable

pushrods up in a straight line to work short and long rocker arms , pivoted

on parallel rocker shafts.

The hemi design was the choice for such marques as Duesenburg , Stutz,

Miller and Offenhauser.

During World War 11, Chrysler was engaged in the development of aircraft engines

and a V-12 tank engine which were to use the hemi head.

James Zeder and Ev Moeller were on the team after the war that looked into the

Hemi for Chrysler. They looked at a Healey engine with a Hemi head and found it

to be the most efficient design that they had seen.

They built a head for a Chrysler six cylinder engine , and called the experimental

unit the A161. It was tested in the real world in a car driven by the head of testing

Wallace Zierer. It passed the test and by 1948 they had a 330 cubic engine called

the A182 , a V8 with hemi heads.

Hemi heads feature HUGE inlet and exhaust valves set at opposing angles in the

head to grab at maximum space created by the half round or " hemi -sphere "

combustion chambers.

This design allowed for short, large inlet and exhaust ports, ideal for almost

straight in and out gas flows.

The Chrysler hemi engines really began as a " back yard " Ford conversion

in the early 1940s.

Zora Arkus Duntov, the legendary Chevrolet guru, had a real hard look at

the famous Ford Flathead engine and he designed a brilliant overhead valve ,

push rod operated Hemi head conversion , which became known as the

Ardun flathead.

This adaptation by Duntov, attracted the attention of the then Chrysler engineers.

In 1951 , the first engine, known as the " Chrysler FirePower " was produced at

331.1 cubic inches and it developed 180 horses at 4,000 rpms. There were 312

foot pounds of torque at 2,000 rpms. This was a 40 % boost in horsepower and

a 16 % increase in torque over the 1950 straight eight engines.

In 1955, the stock version of the same engine boasted 250 horses and the performance

version, with two twin four barrel carburetors and a solid lifter cam resulted in 300

horsepower. The engine cubic capacity was lifted to 356 cubic inches in 1956 and

then to 392 in 1957.

The 392 engine was produced for two years only and they were rated at 325

horsepower and with twin four barrel carburetors this was lifted to 375 horses.

With the factory performance push and it's already inbuilt strength the Chrysler hemi

engine became a popular engine in the late 1950s to the late 1960s as it became a

natural race engine for quarter mile racers.

De soto manufactured five engines, they ranged from 276 and the 291 , to the 330

and 341 cubic inches.

These were known as the " FireDome " and the " FireFlite " engines.

Dodge produced four engines and these consisted of the 241, the 270 that were classed

as low block engines , and the 315 and the 325 cubic inch engines are described as

tall or raised block engines. These engines were known as " Red Ram " engines.

Further descriptions and Engine Identification numbers can be found at other

web-sites that are listed under " Hemi Links " on this web site.