Retro Friday: diesel slant sixes

When the fuel crises of the 1970s hit, American automakers were unprepared. Once Chrysler saw that big car owners were dropping their V8s in favor of newly-available slant sixes to save fuel, they authorized a two-barrel slant six to make the smaller engine more satisfactory—but could they go further?

1977 Slant Six

Chrysler had more than one slant six project, including fuel injection. Today, we’re looking at one of two diesel projects, this one tapping diesel experts at Ricardo to create and test diesel conversions. Chrysler had not made diesel engines for some time, preferring to buy Perkins, Mitsubishi, and other company’s engines for their trucks and European cars.

The work was promising, according to Ricardo’s 1980 paper. They  used glow plugs, fuel injection, and a 21.5:1 compression ratio as a matter of course, expecting to lose 30% of the slant six‘s power during the conversion. The compression and fuel injection mostly made up for the switch from diesel, and they only lost around 10 horsepower. (The slant was rated for around 90 horsepower, net, at the time.) Noise wasn’t a problem with emissions gear installed.

Ricardo addressed several longevity issues but stopped short of adding a turbocharger, because that would hurt durability. In tests with the diesel and a gasoline engine in a Volare, they found the diesel engine ran a 0-60 mph in 20.5 seconds—two seconds slower than the gasoline engine. These were not fast cars! However, gas mileage, on a city/highway cycle, shot up from 18 mpg to 29 mpg with the switch from gasoline to diesel, while emissions fell.

The engine never went into production, though. Light four-cylinders were incredibly popular once the K-cars arrived, at about the same time as Ricard’s report, and the diesel would have been more expensive. Gas prices had fallen back and shortages were already a thing of the past. GM’s poorly thought out diesel conversion didn’t help the project, either.

Full story and charts at

Also at Motales: Leaning Tower of Power (Slant Six)Kaiser’s Tornado SixKangaroo Hemi Six

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