This article documents the process of swapping a GM LS engine into a BMW E46 M3, focusing on the challenges and solutions encountered, particularly regarding the Atech Gm Obdii System. The project began with the acquisition of a Vorshlag LS swap kit.
Header Installation Challenges
The initial hurdle was installing the headers. The passenger side header required removing the starter and motor mount for proper clearance. Trimming the flywheel cover was also necessary to prevent interference. The driver side header presented a different issue: interference with a steering shaft bolt. Even after turning the bolt around, trimming was necessary to achieve a fit, although the header still rested on the bolt. This experience highlighted the importance of test-fitting headers before final engine installation.
Engine and Wiring Installation
With the headers finally in place, the LS engine was installed. The wiring process followed, requiring careful integration of the ATECH GM OBDII system with the BMW chassis.
Addressing Steering and Drivetrain Issues
The original steering shaft interfered with the header, necessitating the installation of a Vorshlag steering shaft. However, even this aftermarket shaft required modification for clearance. Rear differential work revealed broken threads, requiring a Timesert repair and a longer bolt for sufficient thread engagement.
Oil and Cooling System Modifications
A Lingenfelter oil block facilitated the addition of an oil cooler with custom AN fittings welded onto the cooler itself. The stock oil pressure sender was replaced with a remote-mounted unit using an adapter and braided line.
Custom Fabrication and Future Steps
A custom 58-tooth trigger wheel was mounted to the ATI balancer using a machined spacer. A custom power steering pressure line was also fabricated. Remaining tasks include wiring the GM ECU, routing heater lines, installing oxygen sensors (four for the BMW system, two for the LS), installing the differential and driveshaft, and fabricating an exhaust system, potentially incorporating a Corvette bi-modal exhaust for a sleeper look. This LS swap project demonstrates the complexities and custom fabrication often required for successful engine conversions, highlighting the importance of careful planning and problem-solving.
