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1.8L 16v - M42B18
Manufacturers
1.8L 16v - M42B18
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Set of 8 trimetal connecting rod half-bearings for BMW inline-four M40, M42, M43 and M44.
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 share the same connecting rod journal diameter: a single bearing set covers the whole family.
From the factory, these engines are fitted with Glyco connecting rod bearings, BMW part number 11 24 1 284 849 to 854, supplied as half shells graded red and blue: BMW pairs two different grades on the same rod to absorb the machining tolerances of the journal. These are bi-metal bearings, a steel back coated with an aluminium alloy, sized for the loads of a standard engine. As soon as power, engine speed or boost pressure increase, this construction reaches its 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 / King bearings Crankpin Ø 44.973 / 44.991 mm Housing bore Ø 48.000 / 48.016 mm Width 18 mm | OEM reference Crankpin Ø 44.975 / 44.991 mm |
| Reference | Brand and treatment | Size | Wall thickness (mm) OEM : 1.493 |
|---|---|---|---|
| 4B1490H-STD | ACL Race - Untreated | Standard | 1.490 |
| 4B1490HX-STD | ACL Race - Untreated | Std, increased clearance (HX) | 1.477 |
| 4B1490H-.025 | ACL Race - Untreated | +0.025 | 1.503 |
| 4B1490H-.25 | ACL Race - Untreated | +0.25 | 1.615 |
| 4B1490H-.50 | ACL Race - Untreated | +0.50 | 1.740 |
| CR4042XP | King Racing - Untreated | Standard | 1.491 |
| CR4042XP.026 | King Racing - Untreated | +0.026 | 1.504 |
| CR4042XP0.5 | King Racing - Untreated | +0.50 | 1.745 |
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 | 0.049 to 0.058 mm | 0.045 mm - 0.052 mm |
| Increased clearance (HX) | Wider clearance: high oil flow, high rpm | 0.074 to 0.083 mm | |
| +0.025 / +0.026 mm | Polished journal | 0.049 to 0.058 mm | 0.045 mm - 0.052 mm |
| +0.25 mm | Journal reground to 0.25 mm | 0.049 to 0.058 mm | |
| +0.50 mm | Journal reground to 0.50 mm | 0.049 to 0.058 mm | 0.045 mm - 0.052 mm |
Checking on assembly: lay a calibrated strip (Plastigauge) on the journal, torque the rod 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 | 5 Nm + 20 Nm + 70° | |
| Forged rod, ARP2000 (3/8″ × 38 mm) | 61 Nm | 0.140 to 0.152 mm |
| Forged rod, ARP L19 (3/8″ × 38 mm) | 67.8 Nm | 0.152 to 0.165 mm |
ARP recommends the stretch method (gauge).
The ACL and King 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. |
 | King Engine Bearings, an Israeli manufacturer of high-performance engine bearings since the 1960s, offers with its pMax Black trimetal 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, +0.026 and +0.50 mm |
This connecting rod bearing set fits all BMW four-cylinder engines that share the same connecting-rod journal diameter:
| 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 |
