Reinforced ARP cylinder head studs Nissan VQ30DE VQ35DE

The engines concerned

The VQ35DE is Nissan's 3.5-litre petrol V6 (3,498 cc, bore 95.5 mm, stroke 81.4 mm). Naturally aspirated, it powers the Nissan 350Z and the Infiniti G35, among others, as well as the Altima and Maxima. ARP also lists the VQ30, the 3.0-litre V6 of the same family, for this kit: the 202-4701 stud kit is offered for both engines, in 8740, with 12-point nuts.

As original equipment, the VQ35DE cylinder head is held by head bolts with part number 11056-31U10, tightened to 98 Nm, loosened, retightened to 34.3 to 44.1 Nm, then finished with two angles of 90 to 95°. The ARP 202-4701 kit replaces them with M11 x 1.25 studs and 12-point nuts.

Reinforced ARP cylinder head studs

Every combustion cycle pushes the cylinder head upwards. The head fasteners resist it by keeping a constant clamping pressure on the gasket; if that pressure drops, the seal is no longer guaranteed.

For these engines ARP offers kit 202-4701, 8740 studs with 12-point nuts, in M11 x 1.25. The instruction sheet starts with the studs, screwed hand-tight only into the block while the head is still off; the head goes on next, then the nuts, lubricated with ARP Ultra-Torque and tightened in three equal passes, in the manufacturer's sequence. Material of the fasteners: 8740, a chrome-molybdenum steel that ARP specifies at 190,000 psi tensile strength. Factory-fitted fasteners usually fall into classes 10.9 and 12.9, with 150,800 to 176,900 psi minimum tensile strength. In M11 x 1.25, the 8740 studs hold up to 1,000 hp on this V6 engine (calculated estimate).

Technical specifications

Tightening torque

No torque is applied to the studs as they go into the block: they are screwed in by hand. The instruction sheet leaves the option of thread locker to mount them permanently, provided tightening is done before the product hardens.

Before fitting, the instruction sheet calls for every threaded hole in the block to be cleaned, using the ARP 912-0004 thread chaser (M11 x 1.25) where needed, so that engagement is correct and torque readings are accurate.

Where a stud runs into the water jacket, the instruction sheet specifies ARP thread sealer on its block-side threads.

Follow the tightening sequence recommended by the manufacturer and bring to torque in three stages; the stated values assume ARP lubricant on the threads and under the nuts.

The torque figures above come from ARP instruction sheet 202-4701, revision applicable on the day the page went online. The official instruction sheet prevails in case of difference and describes the complete procedure, tightening sequence included. Read the ARP 202-4701 instruction sheet

Technical guide

The stated tightening torques only make sense with ARP assembly grease, applied to the threads and under the nuts.

The ARP brand

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace industry, ARP (Automotive Racing Products) set itself the mission of eliminating engine failures caused by inadequate fasteners in competition. Its thousands of parts are designed and produced in California, in several material grades depending on the application.

Advantages over the original bolts

Criterion	Original head bolts	Reinforced ARP studs
Tightening	Torque, loosening, then two angles of 90 to 95° (98 Nm, then 34.3 to 44.1 Nm)	Torque only, in three equal passes
Block threads	Stressed at every tightening	Spared (studs screwed in by hand)

When studs become necessary

Standard fasteners remain suitable as long as the engine keeps its original combustion pressure. They reach their limits in the following cases:

• VQ35DE or VQ30DE: power raised (turbo, supercharger, hard-tuned naturally aspirated build)
• Compression ratio raised for more power
• Reinforced MLS head gasket, which requires a high and even preload
• Cylinder head that has already lifted or gasket that has already leaked
• Racing or track use, with repeated heat-ups and frequent teardowns

Vehicle compatibility

OEM reference: 11056-31U10 (VQ35DE)

Why is it the most cost-effective solution?

The original VQ35DE head bolts are sized for stock power: as soon as combustion pressure rises, the gaskets and the fasteners are the first to suffer. ARP 8740 studs bring a higher clamp load and keep the gaskets pressed down; redoing both cylinder heads of a V6, with gaskets and labour, costs far more than the kit.

Consider a reinforced head gasket

Reinforced fasteners and the head gasket work together: the gasket must hold the same pressure as the fasteners. The matching gaskets for these engines: