The Story Of How The ‘Gen III’ LT5 Engine That Never Was Came Back To Life

Back in 1986, General Motors purchased Group Lotus, a well-regarded British engine and auto manufacturing firm. GM was in need of a high-performance powerplant for a new version of the C4 Corvette– developed to be the world’s fastest production car– and the chaps at Lotus were well versed in motorsport and engine development.

As a result, Lotus’ work centered around the development of the LT5 engine, a DOHC aluminum-block V8 that had several upgrades over the typical small-block engine found in Corvettes up until that time. Mercury Marine would handle production and assembly.

Initially released in 1990 the Gen I LT5 was good for a respectable 375 hp. The GEN II LT5 was released just three years later and it packed an additional 30 hp, bringing total output to 405 hp. However, the engine platform was scrapped at the end of the C4’s lifespan just two years later. A tragic end to great powertrain, it would seem.

As was typical with other GM projects in the 90’s, the LT5 simply vanished, never to be found under the hood of a C5. Some claim the powerplant was scrapped due to its high costs, while others claim it was ditched due its weight or the fact it was not produced in-house.

But in reality Lotus had already started to develop a GEN III LT5 as far back as 1993, with a target of output of 475 hp. However, GM scrapped the program and blamed OBD-II as the main problem. The official word was that the GEN III would not meet emission standards.

EngineLabs recently had the chance to speak with Graham Behan, one of the Lotus engineers who worked on the project, about his goal of building a working version of the engine GEN III LT5 that never was.

As EngineLabs tells it, Behan “got his hands on some of the development parts” in 1998 and he tried to assemble the engine for several years without success.

Now, as an employee of Lingenfelter, Behan asked Ken Lingenfelter if he could build a special “what if?” ZR-1 build to mark the 25th anniversary of the engine. Luckily, the boss gave Behan the green light, allowing the ex-Lotus employee to finish the project through to completion.

Enginelabs has the official scoop on the build and we encourage you to take a look at how the Gen III LT5 engine that never-was, is unfolding 25-years later.

And yes, Ken plans to one day stuff it into a ZR-1.