Forged connecting rods Ford - 2.5L 20V Turbo - Duratec ST225 (Focus ST) for forged pistons

The Ford Duratec 2.5 turbo engine (five-cylinder)

The Duratec 2.5T is Ford's turbocharged 2.5 L (2,521 cc) inline five-cylinder, with twin overhead cams and twenty valves, directly derived from the modular Volvo “white block”. With an 83 mm bore and 93.2 mm stroke, this long-stroke architecture powers the Focus II ST 225, its Australian XR5 Turbo derivative and the S-MAX 2.5 ST, with outputs from 220 to 226 hp. The same block, in a hotter version (code JZDA), also powers the Focus RS Mk2. As soon as boost and torque rise, the factory fracture-split rod, calibrated for series production, becomes the weak link of the rotating assembly. Replacing it with weight-matched forged rods is the first step in making a prepared five-cylinder reliable.

The forged connecting rods

Drop-forged and precision-machined, these rods take bending, compression and fatigue loads far beyond what the factory 2.5 Duratec rod tolerates. They meet every sporting use: circuit, time attack, drift, drag, rally and hillclimb. Depending on the build, they suit a reliability-focused Stage 1 as well as a Stage 2 or a Stage 3 pushed on boost. Supplied as a complete set of 5, weight-matched, they preserve the five-cylinder's specific rotating-assembly balance. All adopt the 21 mm piston pin, for a 145 mm center-to-center length.

Technical specifications of the Ford 2.5T forged rods (21 mm pin)

Tightening torque and stretch

Rod fasteners are the only part of the rotating assembly whose assembly figure is set by hand: they are also the only place where an operator's error turns directly into engine damage. Too little tension and preload stops covering the inertia load of the five-cylinder: at every revolution the cap separates imperceptibly from the rod, the parting face deteriorates, the shell is hammered, its clearance grows and the oil film eventually gives way at full load. Too much tension and the bolt passes its elastic limit: it keeps a permanent deformation, its preload is gone, the bearing bore loses both size and shape, the big end goes oval and the shell no longer bears evenly. The table below lists, for ARP 2000 as well as ARP L19 fasteners in 3/8", the torque and stretch figures specified by the fastener manufacturer; those values are respected at assembly without adaptation. Stretch read with a dial gauge remains the reference checking method and the kit instructions always prevail.

Forged rods technical guide

4340 forged steel

These rods are forged from 4340 low-alloy nickel-chromium-molybdenum steel, the benchmark for high-performance rods. Forged, then quenched and tempered, it keeps a continuous grain flow that delivers high tensile strength and excellent fatigue life, two decisive assets on a heavily stressed turbo five-cylinder. Against a cost-optimised factory fracture-split rod, a forged 4340 rod gains about +19% yield strength, +8% tensile strength and +19 to +37% in fatigue endurance. It is precisely this margin that absorbs the torque and boost increases of a prepared 2.5T without breakage.

The rod profile

The range is offered in the I profile, by ZRP. The I-beam offers an excellent stiffness-to-weight balance, relevant on a boosted, high-revving 2.5: it limits the moving mass while resisting bending under high boost. The specification table details, for each reference, the center-to-center length, big-end diameter, big-end width and weight.

I profile: I-beam with an optimised stiffness-to-weight ratio, particularly suited to the turbo five-cylinder, where a light rotating assembly matters as much as bending stability.

How to choose your rod bolts?

	ARP 2000: the all-round benchmark alloy, with a tensile strength of about 220,000 psi (1,517 MPa). Offered here in 3/8" diameter, it covers the vast majority of 2.5T builds, up to about 200 hp per cylinder, at speeds reaching 8,500 rpm. Sturdy, reliable and with no storage constraints, it is the default choice for a reliable five-cylinder, from Stage 1 to Stage 3.
	ARP L19: a higher-strength steel, around 260,000 psi (1,793 MPa), reserved for the most demanding builds. In 3/8" diameter, it pushes the limit beyond about 250 hp per cylinder and withstands the high engine speeds of a race build. More corrosion-sensitive, it requires careful storage and race-only use: it is the bolt for extreme configurations.

Measuring bolt stretch

Discover the ARP stretch gauge

The brands offered

This 2.5T range is by ZRP, a specialist in race forged rods. Precision-machined from 4340 steel and weight-matched, its I-profile rods ship as a complete set of 5, with the dedicated ARP bolts (ARP 2000 or L19).

Glossary

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

Vehicle compatibility

These forged rods fit the Fords powered by the 2.5 L turbo five-cylinder (Duratec 2.5T, derived from the Volvo block), first and foremost the Focus ST:

Why is it the most economical solution?

A set of forged rods costs vastly less than a blown engine: on a 2.5T pushed on boost, a factory rod that lets go takes out the block and the crankshaft. By fitting weight-matched forged rods from the outset, you make your build reliable for the long term and spare yourself a full rebuild, for a negligible extra cost next to the price of a new engine.