ACL Race Series main bearings for Subaru Impreza, Forester, Legacy (EJ20, EJ22, EJ25 - #5 spacer)

ACL Race Series main bearings for Subaru Impreza, Forester, Legacy (EJ20, EJ22, EJ25 - #5 spacer), part number 5M8309H. These support the crankshaft in the block and, in a tuned engine, they are responsible for ensuring that oil reaches the entire crankshaft properly.

Internally, they feature three layers on a high-strength steel backing: a copper-lead-tin lining, a thin nickel barrier, and a lead, tin, and copper overlay, which is the surface that works against the crankshaft.

The upper shells have a full 180° oil groove, and the lower shells have a partial groove to ensure oil flow to the connecting rods is not restricted, with the end of the groove being tapered to prevent pressure spikes. Race Series bearings have increased crush and a slightly more eccentric design than standard bearings, both of which are features intended to prevent the bearing from shifting and to maintain proper lubrication when the block and connecting rods deform under load.

In standard size, ACL specifies them for a crankshaft journal diameter of 59.984 to 60.000 mm, and recommends an oil clearance of approximately 0.061 to 0.073 mm for that diameter. If the crankshaft has been ground, the measurement changes.

They do not have the silver tin finish of standard bearings, so their dark color—ranging between brown, black, and bluish—is the factory finish and does not indicate any defect. ACL advises against polishing the surface of the bearings to adjust clearance; if more clearance 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 placing your order.