ACL Race Series main bearings for Alfa Romeo 1300
Fits
Alfa Romeo
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ACL Race Series main bearings for Alfa Romeo 1300, part number 5M1112H. These support the crankshaft in the block and, in a tuned engine, they are responsible for ensuring that oil reaches the entire crankshaft properly.
These are tri-metal bearings: SAE 1010 steel backing, a 0.3 mm copper, lead, and tin layer, a nickel barrier, and a surface overlay of lead, tin, and copper that conforms to the crankshaft surface and resists seizing.
The upper shells feature a full 180° oil groove, while the lower shells have a partial groove to avoid interrupting oil flow to the connecting rods, with a tapered groove end to prevent pressure spikes. Race Series bearings have increased crush and a slightly more eccentric shape than standard bearings, both designed to ensure the bearing remains seated and well-lubricated as the block and connecting rods deform under load.
In standard size, ACL specifies them for a crankshaft journal of 59.959 to 59.972 mm, and recommends an oil clearance of approximately 0.061 to 0.073 mm for this diameter. If the crankshaft has been reground, the measurement changes.
They do not have the silver-tin final coating 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, combine them with the HX version, which provides 0.025 mm of additional clearance.
Before ordering, please confirm your crankshaft measurement (standard or reground); if you have any questions, write to us with your engine code.