It began with an unassuming purchase – a budget-friendly Mercedes C124 from eBay, harboring dreams of a simple engine replacement and a quick resale for profit. However, plans shifted when the C124 caught the eye of my partner, who deemed it a far more stylish choice than my reliable but less fashionable Toyota Avalon. Suddenly, the engine swap project took on a new dimension. Having a history with performance vehicles, including tuned BMW E30s and a Mazda RX-7, the idea of simply replacing the engine felt insufficient. If an engine swap was on the cards, it had to be an upgrade.
Considering local regulations in Victoria, Australia, which restrict older engine installations unless LPG-converted and emissions-compliant, the search for a suitable powerplant began. Initially, a Mercedes V8 from an SL500 was considered, but the AU$5,500 price tag for a front cut seemed steep. While the SL500 shares the W124 chassis foundation, albeit with a modified transmission tunnel, a more economical and equally potent alternative emerged. A 1991 Lexus LS400 (Celsior in Japan) front cut, boasting a remarkably low 52,000km (verified for authenticity), was sourced for AU$2,200. The Lexus LS400’s renowned 1UZ-FE V8 engine promised a significant power boost for the Mercedes C124 project.
(Alt: Front view of a Mercedes C124 project car, hinting at an upcoming engine swap)
The real work commenced amidst long work hours and the crucial task of maintaining a healthy relationship. Disassembling both the Mercedes C124 and the Lexus LS400 revealed a fundamental difference in engineering philosophies. Despite Toyota’s meticulous study of German automotive engineering during the Lexus development, the LS400 embodied a distinct Japanese approach. This meant minimal parts compatibility and components often positioned on opposite sides compared to the Mercedes.
(Alt: A Lexus LS400 1UZ-FE V8 engine, prepared for installation in the Mercedes C124 engine bay during an engine swap project)
To ensure seamless integration, the decision was made to transplant the entire Toyota electrical system behind the Mercedes C124 dashboard, including the Lexus climate control. The interior will retain its Mercedes aesthetic, utilizing the original controls and switches, expertly wired into the Toyota electrical loom to operate the Lexus systems. Integrating the Mercedes C124 instruments with the Lexus electronics also requires adapting the speedometer from mechanical to electric operation, a modification that conveniently allows for a higher reading range beyond the original 220km/h limit. Photos documenting the Mercedes C124 engine swap progress will follow soon, once the misplaced card reader is recovered.
