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1.8L 16v - M42B18
Manufacturers
1.8L 16v - M42B18
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Set of 10 tri-metal crankshaft main bearing half shells for the five main bearings of the BMW M40, M42, M43 and M44 four-cylinder engines.
Launched in 1987, the M40 introduced a new generation of BMW inline four-cylinder engines: cast iron block, single overhead camshaft and two valves per cylinder, in 1.6 and 1.8 litre form. The M42 arrived in 1989 with an aluminium cylinder head, twin camshafts and four valves per cylinder. The M43 replaced the M40 in 1993, still with two valves per cylinder, and the M44 succeeded the M42 in 1995 with displacement raised to 1.9 litres. All of them share the same crankshaft main journal diameter: a single main bearing set covers the whole family.
The crankshaft of these engines runs on five main bearings. Each journal turns between two half shells, one seated in the block and the other in the main bearing cap: they carry the crankshaft. The ACL Race Series and KING RACING tri-metal sets shown here replace them on built engines.
A tri-metal 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 covers the five main bearings of the crankshaft; the ACL set includes one pair of flanged half shells (integrated thrust); the King set is one MB5082XP box of 5 pairs.
An aluminium bi-metal takes around 8,000 psi, a performance tri-metal up to 12,000 psi, 50% more. Hence better resistance and better durability on turbocharged, supercharged and high-revving engines.
| ACL bearings Crankshaft journal Ø 59.971 / 59.990 mm Housing bore Ø 65.000 / 65.019 mm Width 20 mm | King bearings Crankshaft journal Ø 59.972 / 59.990 mm Housing bore Ø 65.001 / 65.019 mm Width 20.0 mm (bearings 1 to 4) and 25.0 mm (bearing 5) |
Manufacturer's note (ACL 5M1538H): the lower half has 2 notches. The set includes a pair of flanged thrust bearings.
| Reference | Brand and treatment | Size | Wall thickness (mm) |
|---|---|---|---|
| 5M1538H-STD | ACL Race - Untreated | Standard | 2.488 |
| 5M1538HX-STD | ACL Race - Untreated | Std, increased clearance (HX) | 2.475 |
| 5M1538H-.025 | ACL Race - Untreated | +0.025 | 2.5005 |
| 5M1538H-.25 | ACL Race - Untreated | +0.25 | 2.613 |
| 5M1538H-.50 | ACL Race - Untreated | +0.50 | 2.738 |
| MB5082XP | King Racing - Untreated | Standard | 2.494 |
| MB5082XP0.25 | King Racing - Untreated | +0.25 | 2.621 |
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 | King XP |
|---|---|---|---|
| Standard (STD) | Standard journal, not reground | 0.061 to 0.073 mm | 0.060 mm - 0.073 mm |
| Increased clearance (HX) | Wider clearance: high oil flow, high rpm | 0.086 to 0.098 mm | |
| +0.025 mm | Polished journal | 0.061 to 0.073 mm | |
| +0.25 mm | Journal reground to 0.25 mm | 0.061 to 0.073 mm | 0.060 mm - 0.073 mm |
| +0.50 mm | Journal reground to 0.50 mm | 0.061 to 0.073 mm |
Checking on assembly: lay a calibrated strip (Plastigauge) on the journal, torque the main cap to spec (see the torque table below), then compare the crushed strip against the gauge to read the clearance.
| Bolts | By torque | By stretch (gauge) |
| Original bolts (OEM), M40, M42, M43, M44 | 20 Nm + 50°, new bolts, washed and oiled |
The ACL and King main 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 tri-metal bearings, available in many sizes and proven on built engines worldwide. |
 | King Engine Bearings, an Israeli manufacturer of high-performance engine bearings since the 1960s, offers with its pMax Black tri-metal alloy bearings designed for heavy loads. |
| Criterion | ACL Race Series | King Racing |
| Cross-section |  |  |
| Type | High-performance trimetal bearing | High-performance trimetal bearing |
| Country of manufacture | Australia | Israel |
| Construction | Trimetal: steel back, copper layer, soft surface | Trimetal: steel back, copper layer, soft surface |
| Alloy | Race Series (copper-lead) | pMax Black (hardened copper-lead) |
| Protective coating | No | No |
| Available sizes | Standard to +0.50 mm (+ increased clearance HX) | Standard and +0.25 mm |
This main bearing set fits all BMW M40, M42, M43 and M44 four-cylinder engines of the following vehicles:
| Brand | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| BMW | 3 Series (E30) 316i | M40B16 | 99–102 hp | 1987–1994 |
| BMW | 3 Series (E36) 316i | M40B16 | 100 hp | 1991–1993 |
| BMW | 3 Series (E30) 318i | M40B18 | 113–115 hp | 1987–1994 |
| BMW | 3 Series (E36) 318i | M40B18 | 113 hp | 1990–1994 |
| BMW | 5 Series (E34) 518i | M40B18 | 113 hp | 1989–1994 |
| BMW | 3 Series (E30) 318i / 318is | M42B18 | 136–140 hp | 1989–1992 |
| BMW | 3 Series (E36) 318i / 318is / 318ti | M42B18 | 140 hp | 1992–1995 |
| BMW | 3 Series (E36) 316i / 316g | M43B16 | 102 hp | 1993–2000 |
| BMW | 3 Series (E46) 316i / 316Ci | M43B16 | 105 hp | 2000–2006 |
| BMW | 3 Series (E36) 318i | M43B18 | 115–116 hp | 1993–1999 |
| BMW | 5 Series (E34) 518i / 518g | M43B18 | 101–115 hp | 1994–1996 |
| BMW | Z3 Roadster (E36) 1.8i | M43B18 | 116 hp | 1995–1998 |
| BMW | 3 Series (E36) 316i | M43B19 | 105 hp | 1999–2000 |
| BMW | 3 Series (E46) 316i / 318i / 318Ci | M43B19 | 105–118 hp | 1997–2002 |
| BMW | Z3 Roadster (E36) 1.9i | M43B19 | 116–118 hp | 1998–2003 |
| BMW | 3 Series (E36) 318is / 318ti | M44B19 | 140 hp | 1995–1999 |
| BMW | Z3 Roadster (E36) 1.9i | M44B19 | 140 hp | 1995–1999 |
