Reinforced ARP bolts and nuts for OEM rods NISSAN RB26DETT RB25DET

The Nissan RB26DETT and RB25DET engines concerned

This kit is intended for the Nissan RB26DETT and RB25DET engines, turbocharged inline six-cylinders of 2.5 to 2.6 litres with twin overhead camshafts and 24 valves: Skyline GT-R from the R32 to the R34, Stagea 260RS, Skyline GT-t and GTS-25t, Laurel and Cedric/Gloria.

It replaces the original rod bolt with an ARP2000 bolt of 11/32 in diameter, pressed into the connecting rod and closed with a nut.

Reinforced ARP bolts and nuts 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.

On stock RB rods, each ARP bolt is pressed in and tightened by a nut; ARP asks for tightening to stop at the stretch read on the gauge, the stated torque being used only when no gauge is available. These bolts are made from ARP2000, an ARP-specific alloy steel heat treated to 220,000 psi tensile strength, with threads rolled once the treatment is complete. Classes 10.9 and 12.9 of standard fasteners start at 150,800 and 176,900 psi: ARP2000 exceeds them by 24 to 46%. The engine speed allowed by the ARP2000 bolts goes up to 10,000 rpm (calculated estimate).

Technical specifications

Before the bolts are pressed in, the ARP instructions have you check that the entry of each rod bore carries a chamfer large enough to leave the radius under the bolt head free.

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 202-6007 instruction sheet, revision in force on the day of publication. Should any difference appear, the official instruction sheet takes precedence. Read the ARP 202-6007 instruction sheet

Assembly is done without thread locker, as the ARP instruction sheet calls for none: ARP Ultra-Torque grease is applied to the threads of each bolt and to the bearing face of its nut.

Once the fasteners are fitted, the ARP instructions call for the big ends to be checked and resized by a machine shop.

Measuring bolt stretch

With the stretch gauge, you read directly how much the bolt stretches during tightening: the dial gauge sits on both ends of the fitted bolt, and tightening stops when the stretch reaches the value in the table. Friction no longer comes into play, hence a more consistent preload on a heavily stressed engine.

Technical guide

Tightening is done with ARP assembly grease, on the bolt threads and on the bearing face of the nuts: 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?

An RB26DETT or RB25DET running higher boost and a higher rev limit puts loads on the rod bolts that the original hardware was not designed to take, and a failure usually destroys the rod, the piston and the block. Fitting ARP2000 bolts costs far less than rebuilding a six-cylinder from this family.

Matching connecting rod bearings

New bolts, new bearings: find below the connecting rod bearings suited to this engine.