ACL Race Series Main Bearing Set, tight clearance — ten tri-metal shells covering all five main journals of the 2.0 litre Theta II turbo block, machined with a thicker wall so the assembled engine runs 0.025 mm (0.001 in) less oil clearance than our standard set.
Read this before you order: this is a clearance grade, not an undersize bearing. ACL list it on the same table as the standard and extra-clearance sets, all three for a crankshaft at standard journal size. It is the tight mirror image of the extra-clearance set we also stock. If your crankshaft has been reground undersize, this is the wrong part — see our 0.25 mm undersize main set instead.
Who it is for. A build where you want a tighter oil film than standard, or a crankshaft that measures slightly under standard through wear or a light polish and needs clearance brought back into specification without a regrind. Tighter clearance holds oil pressure better and quietens a cold start; it leaves less margin for housing distortion, so it suits a controlled build rather than an extreme one.
Fitment — ACL's own application guide names the i30 N. Hyundai i30 N 2018 on, Veloster N 2019-2022, Elantra N 2022-2026 and Kona N 2022-2023 — 2.0L Theta II turbo (G4KH). Journal and tunnel dimensions are unchanged from the standard set; only the wall thickness differs.
From ACL: tri-metal construction, with a lead-tin-copper overlay over a nickel barrier layer and a copper-lead-tin lining on SAE1010 high-tensile steel. Full 180 degree grooved uppers with matching partial grooves in the lowers, tapered groove run-out and enlarged chamfers, so big-end oil supply is never cut off abruptly.
Details: 10 shells, 5 upper and 5 lower, positions 1 to 5; standard journal size with 0.025 mm (0.001 in) reduced clearance; block tunnel bore 56.000-56.018 mm; crank main journal 51.942-51.960 mm; wall approximately 0.0125 mm thicker per shell than the standard set.
Mixing grades is normal practice. ACL expect builders to mix adjacent grades on one journal to reach a target clearance — one tight shell paired with one standard shell halves the change, to 0.0125 mm (0.0005 in). On a main bearing the thicker shell goes in the cap half.
No thrust washers are included. This set is ten shells only, so source thrust washers separately.
A note on appearance. Race Series shells arrive dark and tarnished, with no cosmetic tin flash. Deliberate, not a defect.
Final oil clearance is the engine builder's responsibility. Measure the assembled bearing bores before you commit.
Availability: ON ORDER at our distributor as of 6 November 2026.
Not sure this suits your car? Ask us before ordering — we would rather check the fitment than process a return.