ACL Race Series connecting rod bearings for Opel Z28
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These ACL Race Series connecting rod bearings, part number 6B2270H, are for Opel Z28 engines. They are the standard choice when opening an engine for performance tuning.
Internally, they feature three layers on a high-strength steel backing: a copper-lead-tin lining, a thin nickel barrier, and a lead-tin-copper sliding layer, which is the one that interfaces with the crankshaft. In the connecting rod bearings, the surface layer is thinner to better withstand fatigue.
The Race Series have more housing interference and a slightly more eccentric shape than standard bearings, two details designed so that the bearing does not move and maintains proper lubrication when the block and connecting rod deform under load.
In standard size, ACL specifies them for a rod journal of 55.992 to 56.008 mm, with a bearing width of 18.55 mm. For that diameter, they recommend an oil clearance of about 0.058 to 0.069 mm, measured with a micrometer and bore gauge. If the crankshaft has been reground, the measurement changes.
They do not have the silver tin final 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 at standard size? Write to us with your engine code and we will help you choose.