ACL Race Series connecting rod bearings for Mazda MPS and CX-7 (2.3L L3-VDT DISI Turbo Duratec)
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ACL Race Series connecting rod bearing set for Mazda MPS and CX-7 (2.3L L3-VDT DISI Turbo Duratec), part number 4B8172H. This is ACL's competition range, the same as used in drift, circuit, and drag racing engines.
These are trimetal bearings: an SAE 1010 steel backing, a copper-lead-tin intermediate layer approximately 0.3 mm thick, a nickel barrier, and a lead-tin-copper surface layer that conforms to the crankshaft surface and resists seizure. In connecting rod bearings, the surface layer is thinner to better withstand fatigue.
Compared to a standard bearing, the Race range features more crush, which improves seating and heat transfer, as well as a greater eccentricity that promotes the oil film at high engine speeds.
In the standard size, ACL specifies them for a crankpin diameter of 51.980 to 52.000 mm, with a bearing width of 17.0 mm. For this diameter, they recommend an oil clearance of approximately 0.055 to 0.065 mm, measured with a micrometer and bore gauge. If the crankshaft has been ground, the measurements change.
They do not have the final silver-tin plating of standard bearings, so their dark color—ranging from brown and black to bluish—is the factory finish and does not indicate any defect. ACL advises against polishing the bearing surface to adjust clearance; if more is needed, they are combined with the HX version, which provides 0.025 mm of additional clearance.
Before ordering, confirm the measurement of your crankshaft (standard or ground); if you have any questions, write to us with the engine code.