Lexus unveiled a one-off at the 2003 Sema Show, a IS 300 luxury sport sedan powered by a 4.3-liter V8 engine from a Lexus GS 430. Seeking to demonstrate the potential of the IS 300, Lexus commissioned Rod Millen Special Vehicles (RMSV) to build the car. The resulting IS 430 was completed last week at Millen’s shops in Huntington Beach, Calif.

The potent V8 engine was paired with a Getrag 6-speed manual transmission and lightweight flywheel, which drive the rear wheels through a stronger limited slip differential and GS 430 driveline components.

The concept direction from Lexus required that handling be matched to the high-powered V8 while maintaining reasonable ride comfort and noise levels. TEIN springs and 16-way electronically adjustable shock absorbers work with the original IS 300 front suspension in addition to selected GS 430 rear suspension components, which help ensure durability against the higher torque of the 4.3-liter V8. Large, sticky Michelin Sport Cup tires on 18-inch Speed Star SSR alloy wheels put the power to the ground.

A similar approach was taken with the cooling system and brakes. A GS 430 radiator was fitted to provide ample cooling for the high-output engine. Large Brembo brakes with vented, cross-drilled rotors and four-piston aluminum calipers are there to arrest the newfound acceleration and speed of the IS 430.

Although not a simple conversion, the V8 and 6-speed fit well within the compact IS 300 body structure. Curb weight is slightly higher than the standard IS, some of which is due to larger/stronger components needed to deal with the increased performance and some from the new audio/video system.

‘Fitting the 4.3-liter V8 and six-speed manual transmission to the IS 300 was fairly straightforward,’ said Millen. ‘The larger challenge was to develop an electronic interface that would allow the V8 engine to work with the manual transmission and IS 300 body – something it was never designed to do.’

RMSV’s engineering team met the challenge with expertise developed through years of successful racing and building special vehicles for military and automotive clients. They focused on designing the electronics interface while simultaneously working through the mechanical conversion and enhancements. Numerous parts were specifically fabricated for the IS 430 including stainless steel exhaust headers and dual exhaust system, transmission adaptor, engine and transmission mounts, air intake system, wire harnesses and fluid connectors.

The Lexus IS 430 is a one-off vehicle built to study of the considerable performance potential of the IS 300 luxury sport sedan. There are no plans for a production version.

Story by Lexus, a Division of Toyota Motor Sales, U.S.A., Inc, edited by Supercars.net

In Detail

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