ACL Race Series connecting rod bearings for BMW 316i, 318i, Z3 (M40, M42, M43, M44)
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ACL Race Series connecting rod bearings for BMW 316i, 318i, Z3 (M40, M42, M43, M44) (part number 4B1490H), designed for engines that will operate under much higher loads and higher RPMs than stock.
These are trimetal bearings: an SAE 1010 steel backing, a copper-lead-tin layer approximately 0.3 mm thick, a nickel barrier, and a lead-tin-copper overlay that conforms to the crankshaft surface and resists seizure. In connecting rod bearings, the overlay is thinner to better withstand fatigue.
ACL manufactures them with more "crush" (housing interference) than standard bearings to ensure a secure fit and better heat dissipation, as well as more eccentricity, which helps maintain the oil film when the housing deforms at high RPMs.
In standard size, ACL specifies them for a connecting rod journal of 44.975 to 44.991 mm, with a bearing width of 18.0 mm. For this diameter, they recommend an oil clearance of approximately 0.049 to 0.058 mm, measured with a micrometer and bore gauge. If the crankshaft is reground, the measurement changes.
They do not have the final silver tin plating of standard bearings, so their dark color—ranging from brown and black to bluish—is factory-standard and does not indicate any defect. ACL advises against polishing the bearing surface to adjust clearance; if more is needed, they should be combined with the HX version, which provides 0.025 mm of additional clearance.
Not sure if your crankshaft is standard size? Message us with your engine code and we will help you choose.