ACL Race Series connecting rod bearings for BMW S14/7 Motorsport
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ACL Race Series connecting rod bearing set for BMW S14/7 Motorsport, part number 4B1489H. This is ACL’s competition range, the same used in drift, circuit, and drag racing engines.
The structure is tri-metal, with a steel backing, a copper-lead-tin lining, a nickel barrier, and a soft overlay that conforms and prevents seizure even under very high loads. On the connecting rod bearings, the overlay is thinner to better withstand fatigue.
Compared to a stock bearing, the Race range features higher crush for better seating and heat transfer, and increased eccentricity to promote an oil film when the engine is running at high RPM.
In standard size, ACL specifies this for a rod journal of 44.975 to 44.991 mm, with a bearing width of 16.0 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 of standard bearings, so their dark, brownish-black-bluish color is as manufactured and does not indicate any defect. ACL advises against polishing the bearing surface to adjust clearance; if more is needed, combine them with the HX version, which provides an additional 0.025 mm of clearance.
Not sure if your crankshaft is standard size? Write to us with your engine code and we will help you choose.