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1.6L 16v - W10B16
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1.6L 16v - W10B16
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Set of 8 trimetal connecting rod half-bearings for MINI 1.6 16v W10B16.
Fitted to the first-generation MINI Cooper and One (R50 and R52 convertible), the W10B16 is a 1,598 cc inline four with a single overhead camshaft and 16 valves. All its versions share the same crankpin diameter: a single bearing set covers the whole family.
From the factory, this engine is fitted with standard production connecting rod bearings, sized for the loads of the original engine: as soon as power, engine speed or boost pressure increase, they reach their limits.
A trimetal bearing stacks three layers: a steel back, a copper-lead intermediate layer with high load capacity and an anti-friction running surface that protects the journal. The complete set contains 8 half shells, four pairs for a four-cylinder engine.
The original bearing relies on an aluminium alloy over a steel back, intended for low to medium loads, whereas trimetal is designed for high, sustained loads: an aluminium bi-metal takes around 8,000 psi, a performance trimetal up to 12,000 psi, 50% more. Hence better resistance and better durability on turbocharged, supercharged and high-revving engines.
| ACL bearings Crankpin Ø 43.992 / 44.008 mm Housing bore Ø 47.000 / 47.020 mm Width 16.25 mm |
| Reference | Brand and treatment | Size | Wall thickness (mm) |
|---|---|---|---|
| 4B2903H-STD | ACL Race - Untreated | Standard | 1.489 |
| 4B2903HX-STD | ACL Race - Untreated | Std, increased clearance (HX) | 1.476 |
| 4B2903H-.025 | ACL Race - Untreated | +0.025 | 1.502 |
| 4B2903H-.25 | ACL Race - Untreated | +0.25 | 1.614 |
The running clearance is the gap between the bearing and the journal where the oil film flows.
In operation, the crankshaft journal does not rub against the bearing: it rides on this oil film, which carries the load. Clearance sets the thickness of this film: too tight, oil flows poorly, temperature rises and the risk of seizure increases; too loose, oil escapes, the film loses load-carrying capacity and oil pressure drops. The right clearance is the balance between adequate lubrication and a well-maintained oil film.
| Size / grade | When to choose it | ACL Race Series |
|---|---|---|
| Standard (STD) | Standard journal, not reground | 0.048 to 0.057 mm |
| Increased clearance (HX) | Wider clearance: high oil flow, high rpm | 0.074 to 0.082 mm |
| +0.025 mm | Polished journal | 0.048 to 0.057 mm |
| +0.25 mm | Journal reground to 0.25 mm | 0.048 to 0.057 mm |
Checking on assembly: lay a calibrated strip (Plastigauge) on the journal, torque the rod cap to spec, then compare the crushed strip against the gauge to read the clearance.
The ACL rod bearings shown here are trimetal bearings, designed for engine building and racing. Compared with an original bearing, they handle far higher loads: they cope with increased power, high rpm or the addition of a turbo or supercharger, where a standard bearing quickly reaches its limit.
 | ACL Bearing Company, an Australian manufacturer of high-performance engine bearings since 1949, offers with its Race Series precise trimetal bearings, available in many sizes and proven on built engines worldwide. |
This connecting rod bearing set fits the W10B16 four-cylinder of the following MINI models:
| Brand | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| MINI | MINI (R50, R53) Cooper | W10B16 | 116 hp | 2001–2006 |
| MINI | MINI Convertible (R52) Cooper | W10B16 | 116 hp | 2004–2008 |
| MINI | MINI (R50, R53) One | W10B16 | 90 hp | 2001–2006 |
| MINI | MINI Convertible (R52) One | W10B16 | 90 hp | 2004–2007 |
