ACL Race Series main bearings for Mitsubishi 4G94
Fits
Mitsubishi
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ACL Race Series main bearing set for Mitsubishi 4G94, part number 5M8037H. These support the crankshaft in the block, and in a tuned engine, they are responsible for ensuring that oil reaches the entire crankshaft properly.
The structure is tri-metal, with a steel base, copper-lead-tin lining, a nickel barrier, and a soft surface layer that adapts and prevents seizing even under very high loads.
The upper bearings feature a full 180° oil groove, while the lower ones have a partial groove to ensure oil flow to the connecting rods is not interrupted; the end of the groove is tapered to prevent pressure spikes. ACL manufactures them with more "crush" (housing interference) than standard bearings to ensure a secure fit and better heat dissipation, as well as increased eccentricity to help maintain the oil film when the housing deforms at high RPM.
In standard size, ACL specifies them for a crankshaft journal of 49.982 to 50.000 mm, and for this diameter, it recommends an oil clearance of approximately 0.053 to 0.063 mm. If the crankshaft has been ground, the measurement changes.
They do not have the silver-tin final 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 should be combined with the HX version, which provides an additional 0.025 mm of clearance.
If the crankshaft has been ground or you are unsure of the required size, please write to us with your engine code before ordering.