Reinforced ARP bolts for OEM rods Ford 2.5T Duratec

The Ford engines concerned

The 2.5-litre turbocharged 20-valve inline five-cylinder, originally a Volvo design, was adopted by Ford as the Duratec 2.5T: it sits under the bonnet of the second-generation Focus RS and ST, and of the Mondeo, S-MAX and Kuga. The Focus RS (JZDA) makes 305 hp, the RS500 (HUBA) 350 hp.

On a tuned engine, it is the inertia loads at high rpm that the rod bolt has to carry: the kit therefore replaces the original rod bolt of the standard rods.

Reinforced ARP bolts for connecting rods

At every revolution, the rod bolt takes the pull of the rod and piston assembly, which tries to force the cap away through inertia. As original equipment, it is sized for stock power and is replaced at every strip-down.

This kit replaces the original rod bolts with ARP2000 bolts in M9 x 1, tightened by measuring stretch, the method ARP recommends for this part, or failing that by torque. ARP2000 is an alloy steel developed by ARP and heat treated to 220,000 psi tensile strength; its threads are rolled after heat treatment. Standard engine fasteners commonly fall into classes 10.9 and 12.9, i.e. 150,800 to 176,900 psi minimum strength: ARP2000 sits 24 to 46% above that. In ARP2000, these bolts are rated for 10,250 rpm at most (calculated estimate).

Technical specifications

Tightening torque and stretch

ARP gives priority to stretch control for an accurate preload; the torque in the table is used only when no gauge is available. Torque and stretch figures in the table apply with ARP lubricant.

Figures taken from the ARP 251-6203 instruction sheet, revision in force on the day of publication. Should any difference appear, the official instruction sheet takes precedence. Read the ARP 251-6203 instruction sheet

No thread locker is called for by the ARP instruction sheet for this kit: the bolts are fitted with ARP Ultra-Torque grease, on the threads and under the head.

The ARP instructions for this kit require the big ends to be checked and resized once the fasteners are fitted: this job belongs to an equipped machine shop.

Measuring bolt stretch

Tightening to stretch means setting the preload on how much the bolt actually stretches, rather than on a torque affected by friction. With the bolt fitted, the dial gauge is placed on both its ends and the bolt is tightened until the stretch given in the table is read. It is the safest method on a highly tuned engine.

Technical guide

Tightening is done with ARP assembly grease, on the threads and under the head: the torque and stretch figures in the table were established with it.

The ARP brand

ARP (Automotive Racing Products) came into being in the early 1970s, when Gary Holzapfel, who came from the aerospace industry, decided to tackle the engine failures caused in motorsport by inadequate fasteners. Today the brand produces thousands of part numbers in California for the cylinder head, the main bearings and the connecting rods, in materials suited to each application, with manufacturing known for its consistency.

Vehicle compatibility

Why is it the most cost-effective solution?

On a tuned 2.5T, a rod bolt that fails destroys the rod, the piston and often the block in an instant. In ARP2000, these reinforced and stronger bolts hold higher engine speeds and inertia loads than the original: the fasteners stop being the weak link of the bottom end, for a fraction of the price of a rebuild.

Matching connecting rod bearings

To complete the bottom-end rebuild, we offer the connecting rod bearings intended for this engine.

Why not step up to forged connecting rods?

A forged connecting rod starts as a steel billet, usually 4340, shaped hot under very high pressure: its material is denser and more homogeneous than that of a stock rod. Compared with an original rod, often made of sintered metal and designed for cost, a 4340 forged rod offers about +19% yield strength, +8% tensile strength and +19 to +37% fatigue strength. It is the foundation of a reliable high-power build. For your engine: