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3.2L 24v - S50B32
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3.2L 24v - S50B32
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Set of 6 forged 4340 steel connecting rods for BMW M3 E36 3.2L 24V S50B32.
The BMW S50B32 is the 3.2-litre inline-six that powers the European M3 E36 and Z3 M from 1995. With 3,201 cc (86.4 mm bore x 91 mm stroke), double VANOS, six individual throttle bodies and a 24-valve head, it produces 321 hp at 7,400 rpm — one of the best specific outputs of its era for a production naturally aspirated engine.
A successor to the S50B30, this unit revs high and thrives on sustained loads. But as you raise the rev limit, add forced induction or run regular track days, the factory rotating assembly reaches its limits. These forged connecting rods are the answer to make the bottom end reliable for good.
Cut from wrought 4340 steel, these rods take over from the original parts once the engine leaves its stock range. Forging aligns the metal fibres with the load paths, markedly raising fatigue resistance compared with a sintered rod.
Shot-peened then sorted, they are weight-matched to ±1 g across the whole kit for perfect balance at high rpm. The supplied ARP hardware locks the assembly together and safely allows power gains, the addition of a turbo or long track sessions.
| Reference | Brand | Profile | Bolts | Pin diameter OEM 21 mm | Small-end width | Big-end diameter OEM 53 mm | Big-end width | Center-to-center OEM 139 mm | Weight per rod |
|---|---|---|---|---|---|---|---|---|---|
| R-BMW-004H | ZRP | H | ARP 2000-3/8"-38mm | 21 | 53 | 21.9 | 139 | 550 | |
| R-BMW-004H-L19 | ZRP | H | ARP L19-3/8"-38mm | 21 | 53 | 21.9 | 139 | 550 | |
| R-BMW-004-I | ZRP | I | ARP 2000-3/8"-38mm | 21 | 53 | 21.9 | 139 | 537 | |
| R-BMW-004-I-L19 | ZRP | I | ARP L19-3/8"-38mm | 21 | 53 | 21.9 | 139 | 537 |
| Rod | Bolts | Torque | Recommended stretch |
|---|---|---|---|
| ZRP (R-BMW-004H) | ARP 2000 | 61 N·m | 0.140 – 0.152 mm |
| ZRP (R-BMW-004H-L19) | ARP L19 | 67,8 N·m | 0.152 – 0.165 mm |
| ZRP (R-BMW-004-I) | ARP 2000 | 61 N·m | 0.140 – 0.152 mm |
| ZRP (R-BMW-004-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 is a nickel-chromium-molybdenum alloy steel that rarely combines high strength with good ductility. Against the factory sintered metal, it gains about +19% yield strength, +8% tensile strength and +19 to +37% fatigue endurance. In plain terms: less deformation under load, better absorption of pressure peaks and greater longevity in competition use. |
 | I-Beam profile. Its narrower central section favours lightness and limits moving mass, helping the engine rev. It is an excellent rigidity-to-weight compromise for high-revving naturally aspirated engines such as the S50B32. |
 | H-Beam profile. Its fuller H-shaped section maximises rigidity and bending resistance. It is preferred for high-torque builds or the most severe uses, where strength matters more than chasing grams. |
The rod bolt takes most of the assembly's stress: it keeps the cap perfectly closed on every revolution. Depending on target power and rpm, ARP offers two grades for this kit.
 | ARP 2000: the high-performance benchmark, with no special storage precautions. Handles up to 200 hp per cylinder in 3/8" and 8,500 rpm. Perfect for circuit, trackday, drift, rally, drag or hillclimb — strength, reliability and versatility combined. |
 | ARP L19: designed for engines taken to the extreme — high boost pressure, sustained high rpm, high cylinder pressure. Up to 250 hp per cylinder in 3/8" and 10,000 rpm. More sensitive to corrosion and hydrogen: store and fit it oiled. |
| Beyond torque tightening, measuring bolt stretch with a dial indicator remains the safest way to reach exact 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 S50B32, the range comes in I-Beam or H-Beam profile, with ARP 2000 or ARP L19 hardware, chosen to suit the 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 S50B32 engine and its builds. Vehicles concerned:
| Brand | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| BMW | M3 (E36) | S50B32 | 321 hp | 1995–1999 |
| BMW | Z3 M Coupé/Roadster (E36/7, E36/8) | S50B32 | 321 hp | 1997–2001 |
OEM reference: 11 24 1 406 582 (rod set).
When the bottom end of an M3 E36 3.2 gives way — a bent rod, a breakage on over-rev — the bill climbs fast: specific parts, skilled labour, a car off the road.
For a budget comparable to uncertain second-hand rods, you fit a brand-new forged set here, sorted and made reliable for good. No going back at the next stage of the build.
For the same budget: more margin, more reliability and the peace of mind of a rotating assembly built to last. It is the most rational investment to preserve an iconic engine that has become costly to rebuild.
