ACL Race Series connecting rod bearings for Mitsubishi 4G63, 4G64 (83-92)
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Mitsubishi
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ACL Race Series connecting rod bearings for Mitsubishi 4G63, 4G64 (83-92) (part number 4B1146H), designed for engines that will operate under much higher loads and revs than stock.
Internally, they feature three layers on a high-strength steel backing: a copper-lead-tin lining, a thin nickel barrier, and a lead-tin-copper overlay, which is what works against the crankshaft. On connecting rod bearings, the overlay is thinner to better withstand fatigue.
Compared to a stock bearing, the Race series has more housing crush, which improves retention and heat transfer, and greater eccentricity to promote oil film formation when the engine is revving high.
In standard size, ACL specifies them for a rod journal of 44.991 to 45.000 mm, with a bearing width of 23.5 mm. For that diameter, an oil clearance of approximately 0.049 to 0.058 mm is recommended, measured with a micrometer and dial bore gauge. If the crankshaft is reground, the dimensions change.
They do not have the final silver tin plating of standard bearings, so their dark, brownish-black and bluish color is factory-standard 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 an additional 0.025 mm of clearance.
Not sure if your crankshaft is standard size? Message us with your engine code and we will help you choose.