Reinforced ARP cylinder head studs Nissan VQ30 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 and built from 2000 to 2007, 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 uses cylinder 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°.

Reinforced ARP cylinder head studs

Cylinder head fasteners work constantly: they hold the head tight against the block, crush the gasket to the right value and hold back the push of the gases at every combustion. If they lose even a little tension, the gasket starts to leak.

The ARP 202-4701 kit is supplied as studs with their 12-point nuts, in M11 x 1.25, in 8740.

According to the instruction sheet, the studs are screwed into the block by hand only, before the cylinder head is fitted; the nuts are then tightened with ARP Ultra-Torque assembly lubricant, in three equal passes, following the manufacturer's tightening sequence.

ARP makes these fasteners in 8740, a chrome-molybdenum steel whose tensile strength reaches 190,000 psi. To put this figure in context, original engine fasteners generally belong to classes 10.9 and 12.9, whose minimum ranges from 150,800 to 176,900 psi.

On this V6 engine, the limit of the 8740 studs in M11 x 1.25 lies at 1,000 hp (calculated estimate).

Technical specifications

Tightening torque

The studs are screwed into the block by hand, without torque. Their instruction sheet allows thread locker if they are to be fixed permanently, on the sole condition that tightening is finished before it sets.

The instruction sheet asks you to clean all the block threads, with the ARP thread chaser 912-0004 (M11 x 1.25) if needed, for proper engagement and accurate torque.

If the studs open into a water jacket, their block-side threads are coated with ARP thread sealer.

Tightening to torque is done in three steps, in the order set by the engine manufacturer, with ARP lubricant applied to the threads and under the nuts, a condition for the table values to apply.

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

Gary Holzapfel, a former aerospace engineer, created ARP (Automotive Racing Products) in the early 1970s to tackle engine failures caused by insufficiently strong fasteners in racing. Today the brand develops and manufactures thousands of parts in California, available in several material grades as needed.

Advantages over the original bolts

Criterion	Original head bolts	8740 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

On an engine left standard, the original fasteners do their job. Switching to reinforced fasteners becomes worthwhile as soon as:

• Power raised on a VQ35DE or a VQ30 (turbo, supercharger, hard-tuned naturally aspirated build)
• The compression ratio is increased
• A reinforced MLS gasket is fitted, with its need for a high and even preload
• The head has already lifted or the gasket has already failed
• The engine is used in competition, with intense heat cycles and repeated 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.