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4.0L 32v - S65B40
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4.0L 32v - S65B40
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Set of 8 forged 4340 steel connecting rods for BMW M3 E90/E92/E93 4.0L 32V S65B40.
The BMW S65B40 is the 4.0-litre naturally aspirated V8 (3,999 cc, 92 mm bore, 75.2 mm stroke) that powers the M3 E90/E92/E93. Derived from the S85 V10, it produces 420 hp at 8,300 rpm and 400 Nm, with an 8,400 rpm redline — a sound and a top end that have become legendary.
Built from 2007 to 2013, this screaming V8 handles high revs as standard. But as soon as you build it, raise the limiter or use it hard on track, the factory rods reach their limits — a known weak point on this engine. These forged connecting rods make the bottom end reliable for the long term.
Machined from forged 4340 steel, these rods replace the factory parts once the engine is pushed beyond its stock range. Forging aligns the metal grain with the loads, sharply raising fatigue resistance compared with a sintered rod.
Each rod is shot-peened, inspected and weight-matched to ±1 g across all eight in the set — essential on a V8 that spins past 8,000 rpm. The supplied ARP hardware locks the assembly together and safely allows a build, a raised limiter and long track sessions.
| Reference | Brand | Profile | Bolts | Pin diameter OEM 21 mm | Small-end width | Big-end diameter OEM 56 mm | Big-end width | Center-to-center OEM 140.7 mm | Weight per rod |
|---|---|---|---|---|---|---|---|---|---|
| R-BMW-014-I | ZRP | I | ARP 2000-3/8"-38mm | 21 | 56 | 18.5 | 140.7 | 499 | |
| R-BMW-014-I-L19 | ZRP | I | ARP L19-3/8"-38mm | 21 | 56 | 18.5 | 140.7 | 499 |
| Rod | Bolts | Torque | Recommended stretch |
|---|---|---|---|
| ZRP (R-BMW-014-I) | ARP 2000 | 61 N·m | 0.140 – 0.152 mm |
| ZRP (R-BMW-014-I-L19) | ARP L19 | 67,8 N·m | 0.152 – 0.165 mm |
Manufacturers recommend the stretch-gauge method as the reference: the instructions supplied with the kit always take precedence. The torque figures correspond to assembly with ARP lubricant.
| 4340 steel, a nickel-chromium-molybdenum alloy, combines high mechanical strength with good ductility. Against the factory sintered metal, it gains about +19% yield strength, +8% tensile strength and +19 to +37% fatigue resistance. On an engine that lives at high rpm, this means a rod that is far more durable and tolerant of repeated stress. |
 | I-Beam profile. Its slimmer central section reduces moving mass, a decisive asset on a naturally aspirated V8 that revs as high as the S65B40, while keeping rigidity suited to competition use. |
The rod bolt bears most of the assembly's stress, especially at very high rpm. ARP offers two grades for this kit, depending on target power and rpm.
 | ARP 2000: the high-performance standard, with no storage constraints. Handles up to 200 hp per cylinder in 3/8" and 8,500 rpm. Ideal for circuit, trackday, drift, rally, drag and hillclimb — strength, reliability and versatility. |
 | ARP L19: designed for engines pushed to the extreme — sustained high rpm, high boost pressure, elevated cylinder pressure. Up to 250 hp per cylinder in 3/8" and 10,000 rpm, a relevant choice for an S65B40 taken very high in the rev range. Sensitive to corrosion and hydrogen: store and fit it oiled. |
| In addition to torque tightening, measuring bolt stretch with a dial indicator remains the most reliable way to guarantee preload. The instructions supplied with the kit always take precedence. |
 | ZRP, a Greek specialist in high-performance forged connecting rods, machines its parts from 4340 steel and weight-matches them. For the S65B40, the range comes in I-Beam profile with ARP 2000 or ARP L19 hardware, depending on target power and rpm. |
 | 1) Small end 2) Small-end diameter 3) Rod beam 4) Rod bolt 5) Big end 6) Rod nut / bolt 7) Rod cap 8) Big-end diameter 9) Center-to-center |
These forged connecting rods are compatible with the factory BMW S65B40 engine and its builds. Vehicles concerned:
| Brand | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| BMW | M3 (E90/E92) | S65B40 | 420 hp | 2007–2013 |
| BMW | M3 Cabriolet (E93) | S65B40 | 420 hp | 2008–2013 |
OEM reference: 11 24 7 838 623 (rod set).
On an S65B40, a rod failure at high rpm — a known issue on this V8 — leads to a steep bill: specific block, expert labour, long downtime.
For a controlled budget, making the rotating assembly reliable with a forged set from the start of the build prevents failure and its consequences. An investment far cheaper than a full rebuild.
For the same budget: more reliability, a comfortable rpm margin and the peace of mind of a bottom end built for intensive use. The most rational way to enjoy this exceptional V8 with confidence.
