Reinforced ARP cylinder head studs Nissan KA24DE

The Nissan engines concerned

The KA24DE is Nissan's naturally aspirated 2.4-litre inline four-cylinder, with twin overhead camshafts and 16 valves (2,389 cc, 89 mm bore, 96 mm stroke). It powers the Nissan 240SX and 200SX (S13), the Altima, the Bluebird (U13, U14), the Navara (D22) pick-up and the Xterra, among others. ARP offers a single kit for it, the 202-4304, in ARP2000 studs.

As original equipment, the KA24DE cylinder head is tightened in several torque passes, with a complete loosening in between, then through an angle.

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.

The ARP 202-4304 kit combines ARP2000 studs in M10 x 1.5 with their 12-point nuts.

According to the instruction sheet, the studs are screwed into the block by hand before the cylinder head is fitted; the nuts are then tightened in three equal passes, up to 70 ft-lb.

ARP2000 is an ARP proprietary alloy, heat treated to reach 220,000 psi tensile strength, with threads rolled after heat treatment. Standard engine fasteners mostly belong to property classes 10.9 and 12.9 (150,800 to 176,900 psi minimum): ARP2000 therefore offers 24 to 46 % more margin.

These ARP2000 studs in M10 x 1.5 are calculated to handle up to 600 hp on this four-cylinder 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.

The instruction sheet cites the ARP thread chaser 912-0003 (M10 x 1.5) to clean up the block threads if needed. If the studs open into a water jacket, it says to coat their block-side threads with ARP thread sealer.

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 202-4304, 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 202-4304 instruction sheet

Technical guide

All torque values on this page are given with ARP assembly grease on the threads and under the nuts; another lubricant would make them wrong.

The ARP brand

ARP (Automotive Racing Products) was born in the early 1970s from the initiative of Gary Holzapfel, an engineer from the aerospace industry, determined to eliminate engine failures caused by weak fasteners in motorsport. The company designs and manufactures thousands of parts in California, in several material grades suited to each use.

Advantages over the original bolts

Criterion	Original head bolts	ARP2000 studs
Tightening method	Several passes with an intermediate loosening, then an angle	Torque only, in three passes
Block threads	Stressed at every tightening	Spared (studs screwed in by hand)

When studs become necessary

The original fasteners are sized for the engine as it leaves the factory. They need to be reinforced when:

• Engine moved to forced induction (turbo or added supercharger) or hard-tuned build
• The compression ratio rises as the build progresses
• The original gasket is replaced by a reinforced MLS gasket, which requires a high and uniform preload
• The engine has already suffered a lifted head or a gasket leak
• Competition use imposes severe heat cycles and regular head removals

Vehicle compatibility

Why is it the most cost-effective solution?

The original KA24DE head bolts are sized for stock power: once forced induction or tuning raises the combustion pressure, the gasket and the fasteners are the first to suffer. ARP2000 studs bring a higher clamp load and keep the gasket pressed down; redoing a cylinder head, with gasket and labour, costs far more than the kit.