DC-7

Aerolineas Peruanas DC-7 July 1966

Aerolíneas Peruanas flag carrier of Peru from 1956 to 1971. The tug in the foreground belongs to Braniff International, obviously. Who else would paint an airline tug in such garish colors? 

The DC-7 was the last gasp of piston engined airliners. The design went through several iterations, all designed for longer range and more capacity. At its peak, the DC-7C was flying non-stop between New York and London and from Copenhagen to Tokyo. This didn't last long. The Boeing 707 appeared in 1958 and the Douglas DC-8 (another jet airliner) in 1959. Flying to the Far East was kind of problem back then because you had to fly around the USSR.

The engines they used in the DC-7 were hybrid monsters:

Wright Turbo-Cyclone 18R-3350-TC Radial Engine

This engine powered the last generation of piston engine transports, including the Douglas DC-7 and Lockheed Super Constellation. It represents the end of engine-development that began with the famous Wright Whirlwind, and included an entire family of military and commercial piston power plants. The somewhat unique feature of this engine was a turbo compound device, consisting of an exhaust-driven turbine geared to the crankshaft, generating 20 percent additional take-off power without increasing fuel consumption. - Smithsonian National Air and Space Museum

Wright R-3350 Turbo-Compound Duplex Cyclone
The Turbo is visible in the lower left. Compare with the P-38.

I've heard of turbo-compound engines before. I remember Mack Trucks was experimenting with them an eon ago, and now Mack and Volvo are trying again. They are kind of problematic. You are basically trying to join two forms of incompatible technology that just do not want to cooperate. The first problem is that turbos spin about ten times faster than conventional gas engines, so need gears that can handle the speed and load. A bigger problem might be matching the power output curves. Theoretically, you should get more power and higher efficiency, but as been well established, theory and practice are not the same.

P.S. My dad made a little money off of Braniff stock. I remember mom telling me the "stock split and split and split". Sounds kind of like what Intel stock was doing in the 1980s & 90s.