martin's marine engineering page logo The sun sets on a Maersk box ships sailing in the Indian Ocean, picture by M Leduc, May 2015

Detroit Diesel - North American Diesel icon

Authored by: James Jensen, 2011


Fire TruckThere is not one person in North America who has not, in some form, whether they knew it or not, been impacted by the venerable Detroit Diesel engine. A wartime workhorse, this simple, highly adaptable engine at one time propelled just about every types of heavy North American road vehicle such as buses, fire trucks, and all sorts of heavy equipment. Affectionately knows as "Green Leakers", "Screemin Jimmies", or just "Jimmy", were (are) also extensively found on the water, the Detroit Diesel engine powered many fishing boats and a great many work boats.

This high speed two stroke engine, painted in that iconic "Alpine Green" color, is nearly an oddity to most European engineers and mechanics. Although not as common as twenty years ago, they are still widely found in service in North America. As I type this, there is four aboard this ship I am on now, two 8V92, and two 8V71- not to mention the two EMD main engines.

While going to mechanic school, I always looked forward to that transit bus ride home, the iconic sound of that 671 always put me to sleep for a quick nap. I remember one time, while working in the mechanic division of the Victoria Fire Hall, we had to bring Aerial 3 to the main hall for servicing. During that short trip, that engine lived up to its moniker, Screemin Jimmy. As we drove down the road, I could hear all the car alarms going off, as we went by - I was grinning ear to ear. Being a fire truck there was no restrictions on the noise or power level you pulled from the engine, just get there quickly was the ethos. I will not soon forget the "singing of the pistons" on the first engine I ever rebuilt, a 12V71. If it had not been for the steady sound of that engine at full load on the dyno, my heart would have stopped, I was so excited. To this day, there is no better sounding machine in my mind.

The two stroke Detroit Diesel is no longer in commercial production. The two stroke is just too hard to bring into compliance with modern emission regulations. I am happy to have met James Jensen, a serious enthusiast of Detroit Diesels, who has compiled a short history of the Detroit Diesel engine, with a particular British Columbia flavour; I hope you enjoy.

- Martin Leduc


The Detroit Diesel Engine

Detroit Diesel Inline 4-71In 1938 an engine was introduced that would help bring an end to WW2, and would develop into one of the most versatile engines ever made. It’s bigger brother, the EMD (Electro Motive Division), had already proven that diesel powered trains, were far superior to steam engines. A two-stroke design, with its excellent weight to horsepower ratio, would allow power users to offer the safety and ruggedness of a diesel, where normally a gas engine would be used.

The Series 71 built by Diesel Engine Division of General Motors, was, at first, only available as an inline engine in 3, 4 and 6 cylinder types. The model number 71 describes the amount of displacement per cylinder. These engines ran on the two-stroke principle, with a bore of 4.25” and stroke of 5”. Unit injectors provided the fuel. These engines would go on to be used around the world in many different applications but probably their most important job, was to power almost every landing craft to bring soldiers to the beaches on D-Day, June 6th 1944.

A lot of development had to occur before 1944. To truly understand the story behind the “Jimmy” diesels, we have to go back to 1928, and the relationship between Winton Engine Company, and a GM engineer by the name of Charles Kettering.


The Winton Engine Company : Early Diesels

Alexander Winton had started out building bicycles and automobiles, in which he made his fortunes. In 1911 he built his first yacht which was powered at first by steam. But the inconvenience of having to get the ship ready hours before going out caused him to investigate gas engines. When he was unable to find a suitable manufacturer, he built his own designed as a six cylinder engine with a nine inch bore and 12 ¾” stroke rated at 150HP. These engines did so well that in February of 1912 he decided to manufacturer them under the Winton Gas Engine and Manufacturing Company banner.

Winton quickly moved to building diesel engines, and the first appeared in 1913. By the mid-twenties Winton was recognized as a premier supplier of diesel engines, for both yachts’ and workboats. During this time, Winton embarked on the development of airless injection. In 1928 the first Winton airless injection diesel was built, utilizing a plunger type pump to pump fuel into the manifold, where it was injected into the cylinders, by a cam operated injector valve.

While Winton worked to increase the efficiencies of his engines, many different engine manufacturers were working on reducing the size, and weight of their engines, while increasing rpm so the horsepower to weight ratio could be improved. Their goals were to transform the diesel from a heavy slow speed machine to a high speed, light weight “automobile” type engine.

8-278A Cleveland Diesel Division marine engineWatching all of this was Charles Kettering. Considered by many to be the “presiding genius of the automobile industry”, he had invented such things as the electric starter, safety glass, high compression gas engines and quick drying lacquer paint. In 1928, Mr. Kettering was approached by Alfred P. Sloan, then president of General Motors, with the idea of building diesel engines. Like many automobile executives, Kettering had his own yacht which, at the time, was powered by a Cooper-Bessemer, four stroke, common rail fuel injected engine. He had found this engines fuel system lacking in that the proper amount of fuel could be satisfactorily injected, while at cruising speed but not at any other speeds. He personally spent time to rebuild the entire fuel system, but was still unable to improve on the design.

Figuring he had done all he could, he decided to replace the engines in his yacht with a Winton engines. He had done some research on other engine companies, and was impressed with the work of Winton's chief engineer, Carl DeWitt Salisbury; he was working on a type of fuel injection, that used an individual unit injector for each cylinder. Mr. Kettering wanted his Winton engines equipped with the unit injectors, each weighting 75lbs, but Winton had reservations about this. Mr. Kettering’s wish was granted but the fuel system failed almost right away.

Through Mr. Kettering’s insistence, General Motors began the development of their own unit injector, using a single cylinder, two-stroke engine, known as “Big Bertha”. After much testing, these injectors were finally ready to replace the Winton ones in Kettering’s yacht. The injectors were installed, and immediately put to work for an 18 hour cruise, where they proved to be very reliable. For the next few years, this set of GM injectors was worked on and improved.


GM's first Diesels

After the stock market crash of 1929, GM turned to acquisitions. The company began looking to buy a diesel engine manufacturer, and after considering several companies, including Cummins, GM decided to buy Winton, in 1930. At the same time, General Motors bought Electro-Motive Company which was Winton’s biggest engine purchaser. EMC was a builder of gas-electric rail cars in Cleveland, Ohio. A lot of development and frustration, by Winton took place, trying to not only perfect their fuel system, but also every other piece that makes up an engine. This included development of governors, blowers, and new welded crankcases instead of cast steel. All of this, was an attempt to improve the weight to horsepower ratio.

In 1930, Kettering began his own research into two-stroke diesels, by having Winton build two single cylinder test engines, with 8 inch bores, and 10 inch strokes. One engine was shipped to EMC in Cleveland and the other sent to Kettering’s lab in Detroit. Kettering sent his son Eugene to Cleveland, to work alongside Winton engineer, Carl DeWitt Salisbury, to perfect the injectors to be used in the engines. Development continued on these prototypes and in December, 1932, a 6 cylinder, two-stroke Winton Model 201 began testing.

GM's "Big Bertha" at 1933 worlds fair
GM's "Big Bertha" on exposition at the 1933 Worlds Fair

8-268 EngineFinally, an eight cylinder version of “Big Bertha” was used to power the General Motors exhibition at the 1933 World’s Fair, in Chicago. It was designated the 8-201, and used a 10 inch bore/stroke. It ran at 720 rpm and produced 600HP, with a power to weight ratio of 22:1. These engines were to be used to prove Mr. Kettering’s basic design; commercial applications were not expected to come as soon as they did.

A gentleman by the name of Ralph Budd, was to change all of that. Mr. Budd was a director at Burlington Rock Island Railroad, which was in the process of building a lightweight, streamline train, built of stainless steel. The 8-201 engine was a perfect match for this new train, and in October 1933, the third 8-201 was installed in the Pioneer Zephyr. These engines propelled this train past crowds of people that lined the track, to watch this new style of travel.

Winton 16 201The US Navy began testing a V12 version of the 201 engine, for use in submarines. Producing 950HP at 720RPM, it weight only 12.6 pounds per horsepower. Out of the five companies to submit engines for Navy tests, only the Winton engine was selected. In late November, 1933 the US Navy placed another order with Winton, for sixteen V-16 201A engines, also for submarine power.

Now that the 201 engine was past the test stages and production was ramping up, there were some arguments between Winton and GM, about which direction their business should go. Continue the development of the two-cycle engines, or drop that program and continue with the four-cycle engines. Winton, it seemed, did not want to continue the two-stroke engines, and GM did. There were also infighting between Kettering’s research lab, Winton and EMC.

But development continued and in 1935; Eugene Kettering and Carl Salisbury began development of a successor to the 201A engine. The 201A engine had some short comings and the Model 248; a V-16, rated at 1600HP was introduced as a successor, mainly for use by the US Navy. An increase in cylinder displacement, resulted in the Model 248A and a refinement of simpler construction, resulted in the 278A; an engine that would go on to be used in great numbers, for both the navy, and in postwar years for commercial use in the United States.

Workers at factoryOnce this project was complete in 1936, Kettering and Salisbury brought some Winton engineers down to GM and began designing the Model 567. Designed originally for use in EMC trains, the 567 was introduced in 1938 and took the railroad world by storm. EMC also engineered these engines for marine work; most notably the US Navy’s LST landing craft.

In 1937, GM reorganized Winton as its Cleveland Engine Division, limiting its market, to marine and stationary power. This division continued to develop four-stroke Winton designed engines, as well as two-stroke General Motors designed engines; making this, the only division of GM, to produce four-stroke diesel engines. EMC would continue to develop trains and the 567 engines. In 1941 EMC, was reorganized as Electro-Motive Division of General Motors.

Several different displacement sizes were also developed for the war effort, including the “pancake” engine built by EMD. The 16-184A was a vertical engine with the pistons in a radial design, stacked on top of one another. It was used to power US Navy anti-submarine boats. This design maximized horsepower while minimizing weight and space needed for the engine room.

GM 12V 278A
GM 12V 278A


The birth of GM's 71 Series
1941 factory shot building 4-71 engines
While development on the “big” diesels continued, the two-stroke principal was being applied to a smaller engine. Two single cylinder engines of 3 5/8” bore and 4 ¾” stroke were built; one with direct injection and the other with an antechamber. The goals for these engines were that they be suitable for mass production, and be easily adapted to different applications.

It was recognized that these engines would have an entirely different market compared to its bigger brothers so a separate division was set up. In 1934, GM Diesel Engine Division of General Motors was established. William Crowe, an engineer, working for Kettering, was assigned to this project. Some space at the Cadillac Motor Company was set aside for this fledgling division.

It was decided that the engines, which would go on to become the Series 71, would be available in three sizes; a 3, 4 and 6 cylinder. But these engines were not just scaled down versions of the bigger diesels. The design was the same, but development of the smaller engine had its own problems. Lubrication and supply sources for the blower rotors, almost cut the engine development completely. But these problems were overcome, largely due to Kettering’s belief in the two-stroke theory, and in 1937 the first of these engines came off the line.

Production was limited at first, and then in 1938, almost 700 engines were sent to GM’s Truck and Coach Division, and to Gray Marine for marine conversion. In 1939, the engine was sent to various suppliers, such as Allis-Chambers for use in their tractors.

Before the United States declared war in 1941, US companies were producing equipment for allied countries already fighting the Nazi’s. This included GM Diesel which provided engines for use in tanks, standby generators, road building equipment and other applications, for British and Russian armies. When the U.S. declared war in 1941, GM Diesel was overwhelmed by the demand for their engines.

For the marine side, GM provided EMD, Cleveland Division and Gray Marine with engines without oil pans, exhaust manifolds, flywheel housings, oil pumps, front mounts and cooling systems. This allowed each to develop their own components to work for their needs. As an example, Gray Marine used a chain driven oil pump, while EMD and Cleveland Division used a gear type. Gray Marine concentrated on providing engines for the landing craft program, while EMD and Cleveland built main, and auxiliary engine packages, for tugs and other Navy vessels.


G's 6V53 Millitary applications
Detroit Diesel 6V53 engine for military applications


The 71 goes to war

During World War II, the 71 really showed what it was made of. According to Stan Grayson in his book “Engines Afloat”, 9000 Series 71 engines were built in 1941. That jumped to 62,000 in 1944; and these numbers do not take into account engines built for Gray Marine. At its height of military production, engines were coming off the assembly line at approximately 6000 per month.

Gray Marine really took GM’s engine and made it shine. Power was available in single units up to a quad six arrangement, with either a single shaft or dual shafts. In multiple units, each engine could be taken off line individually, while the others carried on powering the ship. This flexibility, along with simplicity in design, made these engines ideal for war time use.

When looking at the total number of engines GM built for the war effort, 41% went to GM Diesel and EMD/Cleveland Diesel sat at 32.7%. Compared to other manufactures of engines for the war, GM provided 73.7% of the diesel power. Quite an accomplishment for relatively new engines. What might have been even more important to GM Diesel’s success, were the returning servicemen praising and using the many surplus engines, available after the conflict ceased.

Detroit Diesel Inline 6-71 twin power unitA majority of these engines were Gray Marine built Model 64HN9s, with limiting speed governors, and Twin Disc 1.5:1 marine gears. Gray Marine built two different styles of 6-71 marine engines. The first was a standard unit which they describe as a “commercial style”. This engine was rated at 27.5 HP/per cylinder, and used 60mm injectors.

The other style was a “high output Navy style” with “battle rating” of 37.5HP/per cylinder using 90mm injectors. Marked on the governor cover on high output engines, was the word BATTLE; and when placed in this configuration the engine put out a total of 225HP, whereas out of battle mode, it would make 165HP.

There were several other differences between the engines involving injection timing, oil coolers and thermostats, but the basic engine used, was the same. Navy style engines were mounted on frame rails and all vessels using these engines were made to fit these rails, making it quick and efficient to replace defective units.

16-278A Cleveland Diesel Division diesel electric drive, believed to be from a  NYC harbour tug
16-278A Cleveland Diesel Division diesel electric drive, believed to be from a NYC harbour tug

Hoffars Ltd in Coal Harbour, Vancouver

16-184A "Pancake" engine press release photoIn 1938, Hoffars Limited became the GM Diesel marine engine distributor for the west coast of Canada. Originally located at the Southeast corner of Denman and Georgia in Vancouver, Hoffars was also the distributer of Gray Marine gas engines, and Johnston outboards. Hoffars was started by two brothers, Jim and Henry Hoffars; and when the two split ways, Jim became the sole owner of Hoffars Limited. Very few GM Diesels were on the west coast up to 1941, but soon after hostilities ended, surplus Navy 6-71s became readily available. In 1954 Jim Hoffar passed away and his son Peter took over the business and few years later the company moved to a new location on-West 1st Ave at the head of the new False Creek commercial fishing floats.

In 1955, Mr. William (Bill) Hughes went to work for Hoffars Limited, as a Temporary Mechanic and within three months, was moved up to a Journeyman Mechanic working in field service. He remembers Hoffars being a very busy place, with both new engines, and Navy surplus engines. Hoffars would buy the high output surplus engines; rebuild them with in-house modifications, such as replacing 90mm injectors, which were causing over fuelling problems, and replacing with 60mm injectors.

The marine gears were also modified with kits sold by Twin Disc, to change the gear ratio from 1.5:1 to a 3:1. Surplus 6-71’s were not always purchased from the Navy, many came out of generators and even GM Diesel powered tanks. Local owners would buy two engines, using one in their boat and leaving the other as a spare engine. In many instances, it was easier to buy and rebuild a surplus engine, then it was to purchase a new engine from GM.

In the course of his duties, Bill did many startup inspections of engines, either in new or re-powered boats. These inspections included checking the alignment of the installations, hooking up water and fuel lines and horsepower checks. Done with the rocker cover off, “just in case something went wrong”, these horsepower checks on tug boats would include a “dock push”. The tug would be placed up against the dock and the governors buffer screw was taken out. “We would slip a thin screwdriver in there and push the rack all the way to full fuel. We’d look for 1800RPM out of the engine. If they didn’t get that speed then the propeller size was wrong and we wouldn’t give them warranty.” Bill remembers.

On pleasure boats they would do the same test, but they would have to do it in Coal Harbor once they were past the CN Docks, where they were allowed to “open her up”. Bill remembers one wooden tugboat they were testing which had the entire afterdeck under water. There was so much power out of the engine, that the propeller was sucking the back of the boat down into the water.


Detroit Diesel Turbo Charged 8V71GM's post-war developments

In the early 50’s, GM Diesel introduced a new model, called the 6-110. It was only available as an inline six cylinder, and had a continuous rating of 220HP at 1800HP. This engine, along with the 71 series, was available in twin sets, either beside each other, or running inline into a common marine gear. 71 and 110 engines replaced many gas, and slow turning diesels already powering hundreds of tugboats and fish boats along the coast.

Bill can remember seeing Vivian, Atlas, Superior, Washington, Enterprise and Cummins engines being replaced with GM Diesel power. As an example, a 300HP Superior engine, which ran at 360 RPM, was 22 feet long by 8 feet wide, would be replaced by a 6-71’s turning at 1800 RPM loaded, fitting easily into the same area, even allowing more space in the engine room.

In 1950 GM Diesel introduced the Series 51 engine. A valve-less engine rated at 87 HP, it used different port sizes on either side of the liner to allow exhaust gases to escape. Its replacement, the Series 53, came in 1957. This engine powered thousands of boom boats along with log skidders in the forest industry.

Bill Hughes became Preventative Maintenance Mechanic at Hoffars, which involved going to different companies and doing a check list of work on the engines. One engine stands out in Bills memory. One job stand out in his mind, “I did some work for a company that had about 40 boom boats, all tied up; bouncing and banging into each other. I had to do the work at night so everything was done with flash lights. I got down to where the engine was in one and discovered that all four engine mounts were broken. Every time they went forward, the engine moved forward. Every time they went in reverse, the engine slid back. There were deep grooves cut into the cast iron oil pan. That was a Jimmy though.”

The cost of a preventative check was $25 dollars for a 4-53, and $35 for a marine 6-71. But the "Jimmies" always started, so some operators just kept putting them to work and ignored the 'finer points' of routine maintenance.

As GM Diesel’s became more and more popular in B.C.; as well as North America, and the world, newer and better models were being introduced. Improvements to the engines were constantly being developed. In 1957 the Vee type 71 series came out. Available as a V6, V8, V12 and a V16, these engines allowed users to move away from twin, or quad engine installations, to a single 71 engine.

Internal changes included needle valve type injectors, four valves per cylinder, aluminum blocks and turbo charging. Pictures of early turbocharged 71 engines reveal a turbo almost as large as the engine. GM Diesel also produced “inclined” engines which offered a very low profile for marine applications. The inline engines construction also improved. The front of the block could also be the back, the exhaust manifold and blower could both be installed on either side of the block. Some of the main concerns with these engines were their ability to leak oil from every orifice, one of their moniker was "Green Leakers". They also had a tendency to “run away” on their own, when either a governor was set up wrong, stuck racks, or leaking blower seals.

Entering the 1960s, Hoffars Limited was doing very well, and was enjoying a large market share of not just marine sales but industrial and off-road equipment too. This was also a decade of huge growth for Hoffars thanks to the many mines opening up all over BC. With the introduction of the 149 Series in 1967, many mining companies were ordering these engines to power their haul trucks. Hoffars began opening branches across BC to service marine, industrial equipment, off-highway vehicles and on-highway trucks.


1967: The 1,000,000th "Jimmy"

1958 factory photo with 71 series and 110 series engines
1958 factory photo with 71 series and 110 series engines

In 1965 GM Diesel Division was reorganized into the Detroit Diesel Engine Division and in 1967 celebrated building their 1,000,000th engine. In 1970, Detroit Diesel Division and Allison Transmission Division came together to form the Detroit Diesel Allison Division. Locally, Hoffars moved their headquarters to Willingdon Avenue in Burnaby, in 1968.

During the 1970’s Detroit Diesel was enjoying a large share of the overall diesel power industry, and had a commanding hold on the military, bus and marine markets. At the factory, each engine was built to a specific customer order, there were never any “shelf inventory” engines. Each engine was tested and run-in on either an eddy-current or a water brake dyno.

1974 saw the introduction of the Series 92, available in Vee-type with 6, 8, 12, and 16 cylinder models. The 92 had teething problems when first introduced, but GM engineers worked to improve the model, and by the 1980’s many of these problems had been overcome.

In 1976 Robert Cullen, who was Hoffars Ltd's Vice President and General Manager, bought Hoffars, and renamed the company Cullen Detroit Diesel Allison Limited. The business is now known as Cullen Diesel Power Ltd. and is owned by Allan Cullen, Robert's son. Also in 1976, Bill Hughes became Vice President of Parts & Sales; that same year Detroit Diesel built their 2,000,000th engine.

Into the 1980’s, Mr. Kettering’s engines were continually improved, and electronics were introduced which Detroit Diesel called DDEC (Detroit Diesel Electronic Controls). Injector racks were replaced by solenoids and sensors now told an ECM how the engine should perform.


Detroit Diesel Series 149
Detroit Diesel Series 149


EMD from 1954 press releaseThe "Jimmy" in the 21st century

Since 1938, millions of Detroit Diesel two-cycle engines have been installed in BC; and around the world, in every type of application imaginable. Tug boats, buses, logging equipment and power generation. Today Detroit Diesel is a part of DaimlerChrysler’s Power systems division and, along with MTU, still builds new two-stroke engines for the U.S. military.

There are almost 500,000 “screamin jimmies” still working everyday in the world, according to MTU-Detroit Diesel’s website, with a total of 3.5 million two-stroke engines built since 1940. Today though, many Detroit Diesel two-stroke engines are being replaced with more sophisticated, and more fuel efficient four stroke engines such as Detroit Diesels Series 60.

Regardless of the claims of new engines, no other engines comes close to the longevity, and adaptability of the Series 71 engine. Its basic design changed little from 1938; and nothing comes close to the sound of a Jimmy as it steps up to take the load it’s asked to pull. And it takes that load faster, and for longer, for over 70 years, more then any other engine.

Detroit Diesel 24V71Detroit Diesel 24V71 (video)

Videos from YouTube about Detroit Diesel

A promotional video by Detroit Diesel on their History

Modern day Detroit engine factory


Mr. Jensen writes...

" I'm a mechanic by trade, and my Dad works for Cullen Diesel; so did I as a shop cleanup kid, so that's how I got into these engines. I'm always looking for info on these engines, so any avenue where I can meet someone related to these engines is great. I'm still hoping someone might offer me a ride on a Detroit Diesel boat, so I can listen to those engines working hard!! "

If you wish to help him out, you can contact him at "jjbus2000 (at) hotmail  com"

He also sent us these pictures of his hobby engine (s), and writes...

" I have a 1-71 genset, a 4-51 valve-less engine and two 6-71 Gray Marine engines. I did not do the work on the 1-71, but I am currently working on one of the 6-71s, and hope to have it looking, and sounding, as good as the single cylinder. " (Pictured below)

(Some of...) General Motors advertisements for the Detroit Diesel and EMD line of engines


Download all the above advertisements
in a PDF file (6.2MB)

The main article above, was first published in Western Mariner Magazine, April 2011. You can download a copy of the original article here.

You can also follow the development of the Diesel Engine, including that of Detroit Diesel's milestones on the Development Timeline.

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