ACL Race Series connecting rod bearings for Renault 129-5, XZ7R, 150-X5J
Fits
Renault
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These ACL Race Series connecting rod bearings, part number 4B7712H, are for Renault 129-5, XZ7R, and 150-X5J engines. They are the standard choice when opening an engine for performance tuning.
Internally, they feature three layers on a high-strength steel backing: a copper-lead-tin lining, a thin nickel barrier, and a lead, tin, and copper overlay, which is the layer that works against the crankshaft. In connecting rod bearings, the surface layer is thinner to better withstand fatigue.
ACL manufactures them with more "crush" than a standard bearing to ensure they are held firmly in place and dissipate heat better, as well as increased eccentricity, which helps maintain the oil film when the housing deforms at high RPM.
In standard size, ACL specifies them for a crankpin diameter of 44.975 to 44.991 mm, with a bearing width of 19.75 mm. For that diameter, they recommend an oil clearance of about 0.049 to 0.058 mm, measured with a micrometer and bore gauge. If the crankshaft has been ground, the measurement changes.
They do not have the silver tin final plating found on standard bearings, so their dark color—a mix of brown, black, and bluish tones—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 should be combined with the HX version, which provides an additional 0.025 mm of clearance.
Not sure if your crankshaft is at standard size? Write to us with your engine code and we will help you choose.