ACL Race Series main bearings for Honda D17
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- Collection at our shopCartagena, Spain
ACL Race Series competition main bearing set (part number 5M1957H) for Honda D17. These support the crankshaft in the block and, in a tuned engine, the proper oil flow to the entire crankshaft depends on them.
The structure is tri-metal, with a steel backing, a copper-lead-tin lining, a nickel barrier, and a soft surface layer that conforms and prevents seizing even under very high loads.
The upper bearings have a full 180° oil groove, and the lower ones have a partial groove to ensure oil flow to the connecting rods is not restricted, with a tapered groove end to prevent pressure spikes. Compared to stock bearings, the Race series features increased crush for better seating and heat transfer, as well as greater eccentricity to promote oil film thickness at high engine speeds.
In the standard size, ACL specifies this for a crankshaft journal diameter 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 reground, the measurement changes.
They do not have the silver-tin final plating of standard bearings, so their dark, brownish-black-bluish color 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 are combined with the HX version, which provides 0.025 mm more clearance.
If the crankshaft has been reground or you are unsure of the size needed, please email us with your engine code before ordering.