The owner of this 1970 Plymouth Road Runner purchased it in 1986 for $300. Since then he has installed a 159 ci (2.6 L) Detroit Diesel 3-53 inline-three engine connected to a Chrylser four-speed transmission. The engine produces around 101 horsepower and 205 lb-ft of torque and running off a 50/50 mix of diesel and cooling oil returns 25 mpg. The owner has plans of upgrading the injectors and installing a turbocharger which should double the power.
Source: Jon Shaw Youtube channel via BangShift
many of the 3-51’s had a geared blower on industrial applications
that would be an easy off the shelf upgrade