King Engine Bearings MB5578AM0.5 Main Bearing Set BMW Oversize - 318 M40 M42 M43 0.50mm

The King Engine Bearings MB5578AM0.5 is an OE-replacement bi-metal main bearing set designed for BMW 318-series engines equipped with the M40, M42, and M43 engine families (1.6L and 1.8L). This set is sized at +0.50mm oversize, making it the appropriate choice for engines with crankshafts that have been reground to that specification during engine reconditioning or rebuilding.

Constructed using King's AM-series bi-metal aluminum alloy material, equivalent to SAE-783, this bearing set is engineered for low to medium load street and daily-driver applications. The aluminum-based construction provides reliable performance, good conformability, and solid resistance to corrosion for rebuilt engines returning to regular service.

Key Features:

• Oversize: +0.50mm — for use with reground crankshafts
• AM-series bi-metal aluminum alloy construction (SAE-783 equivalent)
• Engineered for BMW M40, M42, and M43 four-cylinder engines (1.6L and 1.8L)
• Main journal shaft diameter range: 59.971–59.990mm (2.3611–2.3618")
• Tunnel/housing bore: 65.000–65.019mm (2.5591–2.5598")
• Bearing length: approximately 24.94mm
• Features King's Bull's Eye Tolerance™ technology — precision machining with computerized wall thickness monitoring for consistent, accurate fitment
• Complete main bearing set for the engine block

King Engine Bearings has been a trusted manufacturer of precision engine bearings since 1960, supplying the automotive aftermarket, aviation, and motorsport industries worldwide. The MB5578AM0.5 is a straightforward, quality replacement solution for BMW 318 engine rebuilds requiring a +0.50mm undersize grind on the crankshaft main journals.