Plymouth 1946-1959, the book

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Plymouth 1946-1959, Sidebar: Diesel Plymouth cars

The mid-1950s are best remembered by enthusiasts as the beginnings of the horsepower race, tailfins, and chrome applied with a trowel. In the Chrysler Corporation laboratories, it was also a time of serious research into alternative forms of powering an automobile. This was not a search for economy, as gasoline was cheap and the Arab oil embargoes were decades away, but a search for viable alternatives to the piston-engine.

1951 desoto diesel

Chrysler's gas turbine program drew reams of publicity, but in the long run, after spending millions of dollars over nearly three decades, the gas turbine program is no closer to production today than it was in the 1950s.

Taking a back seat to the turbine cars was Chrysler Corporation's work with diesel power. The diesel, despite the fact that it probably held greater production line potential than did the turbine, gathered barely more than passing mention in the trade press. The April 1956 Motor Trend mentioned only "that Chrysler is offering a Perkins four-cylinder diesel engine in the Plymouth Belvedere as an alternative to the conventional gasoline engine." Three short lines most readers probably glanced over and quickly forgot.

Perkins diesel engine

Plymouth's diesel engine program was the collaboration of three companies: Perkins Diesel of Peterborough, England; Hunter N.V. of Antwerp, Belgium; and Chrysler's Antwerp subsidiary Societe Anonyme Chrysler. The Antwerp plant was among the oldest of Chrysler's overseas assembly plants; its main purpose to supply locally assembled Chrysler products to the European lowland countries.

Rear of Perkins carHunter N.V. actually developed the Perkins diesel conversions. B. Geerstem, managing director of Hunter, stated, "We developed the Plymouth conversion, based on P4 Perkins engines. A reasonable number were transformed in our own workshop. Most of them went to Belgian taxi companies and for many other professional users."

Perkins P4 engines (Perkins had three "P" series engines in 3-, 4-, or 6-cylinder form) shared a common 5 inch stroke with a choice of 3-1/2in or 3-9/16in bore. Power and torque ratings and further details are on Allpar’s Perkins diesel page.

When Hunter began retrofitting Perkins into Plymouth sedans is uncertain—there is some indication the practice may have gone back as early as the P15 models of the late 1940s.

Proof of a Plymouth diesel's existence surfaced in the Chrysler Historical Foundation archives in 1988 when photos of a 1955 Belvedere sedan were found predating Motor Trend’s 1956 article. Except the word "DIESEL" written across the windshield, the car looked entirely stock. Interior photos of the same car revealed four control knobs—reading heat, start, idle, and stop—not found on regular Plymouths. Detailed photographs of the engine revealed a four-cylinder diesel. Outside of an additional 6-volt battery, the engine compartment was basically stock Plymouth.

1955 Diesel Plymouth Belvedere

While this particular 1955 may have been a one-off to test the feasibility of fitting the Perkins diesel, sources indicate that about 100 1956 diesel-powered cars were built. In its February 1957 issue, Motor Life wrote, "Some experimental work has gone on in the past year with diesel-powered Plymouths in Belgium. The research, involving about 100 limited-production units, was conducted by an English firm called Perkins, which has offices in Canada."

According to Motor Life, these 1956 diesel Plymouths sold for "about $750 over the cost of the same car equipped with a six-cylinder engine"— about $2,700 U.S. 'The idea behind the whole project is to develop something in which the higher initial cost would be offset by lower operating expenses,'* the article said. This was a particularly viable concern in Europe where the price of gas was already high and oversized American-built cars were falling out of favor.

diesel controls

Perkins, which had branches in Canada, apparently saw to it that a handful of diesel-powered cars were shipped there, where at least one car has survived.The diesel experiment was considered enough of a success that plans were made to continue the project into 1957. The 1957 Plymouth, with its much lower hood line (which dictated a “shallow” carburetor in regular production) was considered a major challenge.

diesel Plymouth Savoy

"Whether or not the new combination will be placed upon the market—which might or might not extend to other countries—depends on test results," Motor Life commented. The October 1959 Motor Life later reported, "Plymouth diesels are being seen more and more in taxicab fleets from coast to coast. Under-hood unit is the Perkins diesel. While they may be successful in cab operations, where continuous running is a factor, they are unlikely to be worthwhile as a private vehicle. The added cost of diesel installation could not be offset by fuel savings in life of the engine."

Nothing more was reported on the project, and whatever development took place went unnoticed by the U.S. trade press. Hunter N.V. continued to make Perkins diesel conversions and still does to this day—a current project finding a Perkins 6.247-liter diesel placed into a Jaguar XJ6! During its heyday, even Valiants were commonly converted to diesel power.

Perkins diesels and Chrysler Corporation vehicles

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