Development of the PW1120 to Israeli Air Force (IDF/AF) specifications began in June 1980. It retained the F100 digital electronic control system, along with the F100 main module transmission fuel pump forward channels, with only minor modifications. Unique PW1120 components include a wide-chord low-pressure (LP) compressor, a single-stage uncooled low-pressure (LP) turbine with a simplified single-flow booster, and a lightweight convergent/divergent nozzle. Full-scale testing began in June 1982, and the PW1120’s flight permit testing began in August 1984. The PW1120 had a 70% similarity to the F100, so the IDF/AF would not need a dedicated facility for spare parts. It was to be built under license by Bet-Shemesh Engines Limited in Israel.

IAI installed a PW1120 on the starboard bed of an F-4E-32-MC of the IDF/AF (Number 334/66-0327) to explore the airframe/engine combination for an upgrade program for the F-4E known as the Kurnass 2000 (“Heavy Hammer”) or to serve as an engine testbed for the Super Phantom and Lavi. The engine was more powerful and more fuel-efficient than the General Electric J79-GE-17 turbojet normally fitted to the F-4E.

Structural changes included modified air intake ducts, new powerplant ports, new or modified powerplant bay doors, integrated drive generators, and a new fuselage-mounted gearbox with an autothrottle system. It also included a modified bleed management and air conditioning ducting system, modified fuel and hydraulic systems, and a powerplant control/airframe interface. It first flew on 30 July 1986.

Two PW1120 power plants were installed in the same F-4E and first flew on 24 April 1987. This proved very successful, allowing the Kurnass 2000 to exceed Mach 1 without afterburners and have a combat thrust-to-weight ratio of 1.04. This improved the sustained turn ratio by 15 percent, the climb rate by 36 percent, mid-level acceleration by 27 percent, and the low-level speed from 1,046 km/h to 1,120 km/h (654 to 700 mph) with 18 bombs (or 565 kn to 605 kn). It was demonstrated at the 1987 Paris Air Show.