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3.5L 12v - M30B35 - BMW
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3.5L 12v - M30B35 - BMW
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Set of 6 forged 4340-steel connecting rods for BMW 6-cylinder M30.
The M30 is BMW’s large inline-six, nicknamed the “Big Six”, built from 1968 to 1994. With a cast-iron block, an aluminium cylinder head and a chain-driven overhead camshaft with two valves per cylinder, it powered the brand’s upper-range saloons and coupés, from the 5, 6 and 7 Series to the E9 coupés. The family covers four displacements sharing the same connecting rod: M30B28 (2.8L), M30B30 (3.0L), M30B32 (3.2L) and M30B35 (3.5L).
Renowned for its smoothness and longevity, the M30 runs on a sturdy seven-bearing crankshaft that makes it an excellent tuning base. Its turbocharged version (745i Turbo) and the ALPINA derivatives show its potential. The original rods, however, remain the limiting link as soon as power or rpm rise significantly.
Machined from high-strength 4340 steel and then heat-treated, these forged connecting rods replace the M30’s original rods to withstand the higher revs and cylinder pressures of a build without flinching. Forging aligns the metal’s grain flow and removes casting porosity: the result is markedly higher fatigue strength and the safety margin that becomes essential as soon as power climbs.
Each set is inspected and balanced, then supplied with high-performance ARP bolts sized for the target torque. Paired with forged pistons, these rods form the basis of a reinforced bottom end, able to endure intensive use and competition.
| Reference | Brand | Profile | Bolts | Pin diameter OEM 22 mm | Small-end width | Big-end diameter OEM 52 mm | Big-end width | Center-to-center OEM 135 mm | Weight per rod |
|---|---|---|---|---|---|---|---|---|---|
| R-BMW-013-I | ZRP | I-Beam | ARP 2000-3/8"-38mm | 22 mm | 52 mm | 23.9 mm | 135 mm | 496 g | |
| R-BMW-013-I-L19 | ZRP | I-Beam | ARP L19-3/8"-38mm | 22 mm | 52 mm | 23.9 mm | 135 mm | 496 g |
| Connecting rod | Bolts | Tightening torque | Recommended stretch |
|---|---|---|---|
| ZRP (R-BMW-013-I) | ARP 2000 | 61 N·m | 0.140 – 0.152 mm |
| ZRP (R-BMW-013-I-L19) | ARP L19 | 67.8 N·m | 0.152 – 0.165 mm |
Manufacturers recommend the bolt-stretch method (stretch gauge) as the reference: the instructions supplied with the kit always take precedence. The quoted torque figures are for assembly with ARP lubricant.
| 4340 steel is a nickel-chromium-molybdenum alloy steel used in aerospace and motorsport alike. Forged then heat-treated (quench and temper), it offers excellent tensile strength, high fatigue resistance and real ductility. Compared with an original rod (often sintered/powder metal, optimised for series-production cost), a 4340 forged rod shows roughly +19% higher yield strength, +8% higher tensile strength and above all +19% to +37% higher fatigue strength, i.e. a fatigue life under cyclic loading several times longer. This is what makes forged 4340 the reference material as soon as boost and rpm climb. |
 | I-Beam profile. With its slimmer central section, the I-beam rod favours light weight and an excellent stiffness-to-mass ratio. It is the most common profile, perfectly suited to BMW M30 builds, from a reinforced engine to high power levels. |
The rod bolt is one of the most heavily stressed parts in the engine. The key is to match the ARP grade to the real use of the build, then to strictly follow the assembly torque and stretch.
 | ARP 2000 (tensile strength ~220,000 psi, i.e. ~1,517 MPa) is the high-performance standard. Suited to builds up to 150 hp per cylinder with 5/16" bolts or 200 hp per cylinder with 3/8" bolts, and up to 8,500 rpm, it is the most common grade in circuit, track days, drift, rally, drag and hillclimb, recognised for its strength, reliability and versatility, with no particular storage constraints. |
 | L19 (tensile strength ~260,000 psi, i.e. ~1,793 MPa) is designed for engines pushed to the extreme, up to 200 hp per cylinder with 5/16" bolts or 250 hp per cylinder with 3/8" bolts, and up to 10,000 rpm: very high boost pressure, sustained high rpm and high cylinder pressure. It is the choice for big-power builds: drag racing, drift, rally and circuit use. Caution: sensitive to corrosion and hydrogen embrittlement, it must always be stored and fitted oiled, away from moisture. |
In addition to torque tightening, measuring rod-bolt stretch is the most reliable check for optimal preload. The check is done with the bolt fitted: place the gauge (dial indicator) on the two ends of the bolt and read its actual stretch, which must match the recommended value (see the torque & stretch table above). This method removes the friction variations inherent in torque tightening and secures the assembly on heavily stressed engines. |
 | ZRP, a Greek brand of high-performance forged connecting rods, designed by Alex Drakos in Athens. Each rod is forged from 4340 steel, precision-machined and balanced to ±1 g to stay reliable at high rpm. Available in I-beam or H-beam profile with ARP 2000, L19 or Custom Age 625+ bolts, they are designed and inspected in Greece, and proven in rally, on circuit and in drift. |
 | 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 fit all BMW M30 inline-six engines, from 2.8 to 3.5 litres, that share the same rod. The table below lists the models (with chassis code), engine code, power and model years:
| Make | Model (chassis) | Engine code | Power | Years |
|---|---|---|---|---|
| BMW | 2800 CS Coupé (E9) | M30B28 | 170–192 hp | 1967–1974 |
| BMW | 2500 / 2.8 (E3) | M30B28 | 170–173 hp | 1968–1977 |
| BMW | 528 / 528i (E12) | M30B28 | 165–184 hp | 1975–1981 |
| BMW | 528i (E28) | M30B28 | 184 hp | 1981–1987 |
| BMW | 628 CSi (E24) | M30B28 | 184 hp | 1979–1987 |
| BMW | 728 / 728i (E23) | M30B28 | 170–184 hp | 1977–1986 |
| ALPINA | B6 (E21/E30) | M30B28 | 200–218 hp | 1978–1986 |
| BMW | 3.0 CS / CSi Coupé (E9) | M30B30 | 180–200 hp | 1970–1976 |
| BMW | 2500–3.3 (E3) 3.0 | M30B30 | 179–200 hp | 1971–1977 |
| BMW | 530i (E12) | M30B30 | 178 hp | 1974–1978 |
| BMW | 530i (E34) | M30B30 | 188 hp | 1988–1990 |
| BMW | 630 CS / CSi (E24) | M30B30 | 178–185 hp | 1976–1979 |
| BMW | 730 (E23) | M30B30 | 184 hp | 1977–1979 |
| BMW | 730i / 730iL (E32) | M30B30 | 188–197 hp | 1985–1994 |
| ALPINA | B7 (E12/E24) | M30B30 | 301 hp | 1978–1982 |
| ALPINA | B10 (E34) | M30B30 | 231 hp | 1993–1996 |
| BMW | 3.0 CSiL (E9) | M30B32 | 206 hp | 1974–1975 |
| BMW | 3.2 Li (E3) | M30B32 | 200 hp | 1975–1977 |
| BMW | 333i (E30) | M30B32 | 197 hp | 1985–1987 |
| BMW | 533i (E28) | M30B32 | 184 hp | 1982–1984 |
| BMW | 633 CSi (E24) | M30B32 | 179–200 hp | 1975–1984 |
| BMW | 732i / 733i / 745i (E23) | M30B32 | 177–252 hp | 1977–1986 |
| BMW | M535i (E12) | M30B35 | 218 hp | 1980–1981 |
| BMW | 635 CSi (E24) | M30B35 | 218 hp | 1978–1982 |
| BMW | 735i (E23) | M30B35 | 218 hp | 1979–1982 |
OEM references (per engine): M30B28, M30B30, M30B35 11 24 0 618 006 ; M30B32 11 24 1 260 306.
On these now-classic inline-sixes, replacing a tired original rod with a new genuine part is expensive and offers no extra margin against a power increase.
For a comparable budget, fitting 4340 forged connecting rods changes everything: the part is new, stronger than the original and built to handle torque and rpm. A lasting investment rather than a like-for-like repair.
For the same budget: more reliability, more potential and real peace of mind to drive hard. That’s the whole point of reinforcing the M30 with forged rods as soon as the bottom end is opened up.
