ACL Race Series main bearings for Nissan 350Z 313 bhp and 370Z (VQ35HR, VQ37VHR)
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ACL Race Series main bearing set for Nissan 350Z 313 bhp and 370Z (VQ35HR, VQ37VHR), part number 4M2505H. These support the crankshaft in the block and, in a tuned engine, are responsible for ensuring oil reaches the entire crankshaft correctly.
They feature a tri-metal structure with a steel backing, a copper-lead-tin lining, a nickel barrier, and a soft overlay that conforms and prevents seizing even under very high loads.
The upper shells have a full 180° oil groove, while the lower shells have a partial groove to avoid restricting oil flow to the connecting rods; the end of the groove is tapered to prevent pressure spikes. Compared to stock bearings, the Race range has greater crush for improved retention and heat transfer, as well as increased eccentricity to promote an oil film at high engine speeds.
In standard size, ACL specifies them for a crankshaft main journal diameter of 64.951 to 64.975 mm, and recommends an oil clearance of approximately 0.065 to 0.078 mm for that diameter. If the crankshaft has been reground, the required size will change.
They do not have the silver-tin final plating of standard bearings, so their dark, brownish-black and bluish color is the factory finish and does not indicate any defect. ACL advises against polishing the bearing surface 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.
Not sure if your crankshaft is standard size? Write to us with your engine code and we will help you choose.