ACL Race Series main bearings for Alfa Romeo 3.2L V6 JTS
Fits
Alfa Romeo
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ACL Race Series competition main bearing set (part number 4M2273H) for Alfa Romeo 3.2L V6 JTS. These support the crankshaft in the block and, in a tuned engine, are essential for ensuring oil properly reaches the entire crankshaft.
The structure is tri-metal, with a steel backing, copper-lead-tin lining, nickel barrier, and a soft overlay that conforms and prevents seizing even under very high loads.
The upper bearings feature a full 180° oil groove, while the lower bearings have a partial groove to ensure oil flow to the connecting rods is not restricted; the end of the groove is tapered to prevent pressure spikes. Compared to stock bearings, the Race range has increased crush for better seating and heat transfer, and greater eccentricity to promote an oil film at high engine speeds.
In standard size, ACL specifies this for a crankshaft journal diameter of 67.992 to 68.008 mm, and recommends an oil clearance of approximately 0.067 to 0.081 mm for this diameter. If the crankshaft has been reground, the measurement changes.
They do not have the final silver tin 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 are combined with the HX version, which provides an additional 0.025 mm of clearance.
Not sure if your crankshaft is standard size? Write to us with your engine code and we will help you choose.