Forged connecting rods BMW - 1.8L / 1.9L 16V - M42B18 / M44B19 for forged pistons

The BMW M42 / M44 engine

Launched in 1989, the M42 was BMW's first four-cylinder with double overhead camshafts and sixteen valves. With a 1,796 cc displacement (84 mm bore, 81 mm stroke), it pairs a sturdy cast-iron block with an aluminium cylinder head, chain-driven timing and hydraulic lifters. It powers the sporty 318is versions and comes as a saloon, coupé, convertible and compact.

In 1995 the M44 took over, with displacement raised to 1,895 cc (85 mm bore, 83.5 mm stroke) for around 140 hp. It is found on the E36 3 Series 318is, 318ti and 318i convertible, as well as on the Z3 1.9 roadster. Smooth and eager at high revs, these engines make an excellent basis for tuning: as soon as you raise boost pressure, compression ratio or engine speed, switching to forged connecting rods secures the bottom end.

Forged connecting rods

Forged from high-strength 4340 steel, these reinforced connecting rods protect the bottom end as soon as power rises. They become essential when fitting forged pistons, raising engine speed, increasing boost pressure or gaining displacement.

Designed to withstand the heavy loads of tuned engines, both forced-induction and high-revving naturally aspirated, they cover every discipline: rally, drift, drag racing, circuit, hillclimb and time attack, and support Stage 2 to Stage 4 builds and beyond.

Technical specifications, BMW M42 / M44 forged connecting rods

Tightening torque & bolt stretch

The two bolts of a given cap form an inseparable pair: bringing them to the final value one after the other tilts the cap and distorts the bearing bore, even if the reading is correct at the end. On the M42B18 and M44B19, both bolts are therefore brought up together, taken through a common intermediate stage, then to the final figure from the table above with one more alternation. That figure, like the associated stretch range, is the bolt manufacturer’s and varies depending on whether the rod carries ARP 2000 or ARP L19: it is observed without interpretation. Since torque remains sensitive to thread friction, stretch measured with a dial gauge is still the reference check on the eight bolts. Clean threads, an even coat of ARP assembly lubricant. In case of contradiction, the kit instruction sheet wins.

Technical guide

Forged 4340 steel, what is it?

Connecting rod profiles

I profile. The I-beam section favours light weight: less material in the rod beam, hence less inertia and a real ability to rev high. It is the reference profile for high-revving naturally aspirated engines and modern turbo builds, where controlling moving mass is key.

How to choose your rod bolts?

Rod bolts are among the most heavily loaded parts of the engine. The right choice means matching the steel grade to the real use of the build, then respecting the assembly torque and stretch.

ARP 2000. A high-performance standard, it covers up to about 200 hp per cylinder in 3/8" and a maximum engine speed of around 8,500 rpm. Versatile and reliable, with no particular storage constraints, it suits circuit, trackday, drift, rally, drag racing and hillclimb.

ARP L19 (tensile strength of approximately 260,000 psi, or ~1,793 MPa). Designed for engines pushed to the extreme (very high boost pressure, sustained high revs, high cylinder pressure), it accepts up to about 250 hp per cylinder in 3/8" and speeds near 10,000 rpm. It is the choice for big builds in drag racing, drift, rally and circuit. Sensitive to corrosion and hydrogen embrittlement, it must be stored and fitted oiled.

Measuring bolt stretch

Buy the ARP stretch gauge →

The brand offered

ZRP. A Greek brand of high-performance forged connecting rods, made by Drakos Engineering in Athens. Each rod is forged from 4340 steel, precision-machined and balanced to ±1 g to stay reliable at high revs. Offered here in I profile with ARP 2000 or ARP L19 bolts, they are designed and inspected in Greece for rally, circuit and drift.

Glossary

1) Small end 2) Small-end diameter 3) Rod beam 4) Rod bolt 5) Big end 6) Nut / rod bolt 7) Rod cap 8) Big-end diameter 9) Center-to-center

Vehicle compatibility

Below is the list of vehicles equipped with the BMW 1.8L / 1.9L 16V M42B18 / M44B19 engine. The piston pin diameter and the centre-to-centre length must be confirmed on your engine before ordering.

OEM reference: 11 24 1 437 617 (rod set).

Why it is the most cost-effective solution

On a tuned M42 or M44, a connecting-rod failure almost always destroys the block and cylinder head. A set of forged rods costs a fraction of a new engine and a long downtime. It is the guarantee of a reliable bottom end, able to handle the target power for the long run, mile after mile.