Reinforced ARP bolts for OEM rods NISSAN VR38DETT

The Nissan engine concerned

This kit is intended for the 3.8-litre Nissan VR38DETT twin-turbo V6 (95.5 mm bore, 88.4 mm stroke, 3,799 cc), fitted since 2007 to the GT-R R35, from the 485 hp version to the 600 hp NISMO.

The original connecting rod bolt of the VR38DETT is replaced, on each of the rods, by an ARP bolt in Custom Age 625+.

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.

The Custom Age 625+ bolts in this kit are best tightened by the stretch read with a gauge; the ARP instruction sheet gives a torque of 81.3 Nm for the case where that instrument is not at hand. CA625+ (Custom Age 625+) is a super-alloy that ARP rates at a typical tensile strength of 260,000 to 280,000 psi. ARP highlights its long fatigue life, its toughness, its complete resistance to atmospheric corrosion and oxidation, and its immunity to both hydrogen embrittlement and stress corrosion. Standard engine fasteners, for their part, mostly belong to classes 10.9 and 12.9, i.e. 150,800 to 176,900 psi minimum strength.

Technical specifications

The ARP instruction sheet states that the bolt hole of the rod cap needs a sufficient chamfer to clear the radius under the head, and that each bolt is fitted without a washer.

Tightening torque and stretch

For this part, ARP favours tightening to a measured stretch, the key to an exact preload; torque is given only when no gauge is available. The figures in the table assume ARP lubricant.

The values above come from the ARP 202-6101 instruction sheet applicable at the date of publication; it is authoritative in the event of any difference. Read the ARP 202-6101 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.

According to the ARP instructions, the big ends must be checked and resized with the fasteners in place; plan a visit to 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

Torque and stretch figures are only valid with ARP assembly grease, applied to the threads and under the head.

The ARP brand

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace sector, ARP (Automotive Racing Products) was born to put an end to fastener-related engine failures in racing. Its thousands of part numbers, designed and manufactured in California for the cylinder head, the main bearings and the connecting rods, come in several materials depending on the application and are recognised for the consistency of their manufacture.

Vehicle compatibility

Why is it the most cost-effective solution?

On a VR38DETT run at a higher boost pressure and engine speed, each rod bolt sees ever greater tensile loads, and a single bolt that breaks destroys the rod, the piston and the V6 block. A set of Custom Age 625+ ARP bolts protects that point for a sum far below that of rebuilding a GT-R bottom end.

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 rod, hot formed under high pressure from a steel such as 4340, gains density and homogeneity compared with a stock rod. Where the original rod, often made of sintered metal, is aimed first at cost, a 4340 forged rod shows about +19% yield strength, +8% tensile strength and +19 to +37% fatigue strength. It is the cornerstone of a solid high-power build. For your engine: