ACL Race Series main bearings for Honda F23
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- Collection at our shopCartagena, Spain
ACL Race Series main bearing set for Honda F23, part number 5M1957H. These support the crankshaft in the block and, in a tuned engine, are responsible for ensuring that oil reaches the entire crankshaft properly.
These are tri-metal bearings: SAE 1010 steel base, a copper-lead-tin layer approximately 0.3 mm thick, a nickel barrier, and a surface layer of lead, tin, and copper that conforms to the crankshaft surface and resists seizing.
The upper bearings feature a full, 180° oil groove, while the lower bearings have a partial groove to avoid restricting oil flow to the connecting rods; the end of the groove is tapered to prevent pressure spikes. ACL manufactures them with more "crush" (housing interference) than standard bearings to ensure they are held securely and dissipate heat better, as well as greater eccentricity, which helps maintain the oil film when the housing deforms at high RPM.
In standard size, ACL specifies them for a crankshaft journal of 54.980 to 55.000 mm and recommends an oil clearance of approximately 0.057 to 0.068 mm for this diameter. If the crankshaft has been ground, the measurements will change.
They do not have the silver tin finish of standard bearings, so their dark color—ranging from brown to 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 clearance is needed, combine them 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.