Reinforced ARP cylinder head studs Toyota 2JZ-GE 2JZ-GTE

The engines concerned

The 2JZ-GE and 2JZ-GTE are Toyota 3.0-litre, 24-valve inline six-cylinder engines (2,997 cm³, 86 mm bore and stroke), the GE naturally aspirated and the GTE twin-turbocharged. For the Dart (2JZ) iron block, ARP offers a single stud kit, the 403-4301, in CA625+, with 12-point nuts and an M11 x 1.25 thread.

As standard, the 2JZ-GE and 2JZ-GTE cylinder head is held by 14 Toyota head bolts (part number 90910-02102), tightened to 34 Nm and then through two 90° stages, which this kit replaces.

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.

For the Dart (2JZ) iron block the ARP catalogue lists the 403-4301 kit, in CA625+, with 12-point nuts and an M11 x 1.25 thread. The CA625+ version is made from Custom Age 625+, a super-alloy whose tensile strength typically lies between 260,000 and 280,000 psi. It combines long fatigue life and high toughness, is not affected by atmospheric corrosion or oxidation, and remains immune to hydrogen embrittlement and stress corrosion. To put these figures in context, original fasteners generally fall into classes 10.9 and 12.9, between 150,800 and 176,900 psi minimum tensile strength. As an estimate, the M11 x 1.25 studs in CA625+ withstand up to 1,100 hp on this six-cylinder (calculated estimate).

Technical specifications

Tightening torque

Technical guide

When assembling, the threads and the nut bearing faces receive ARP Ultra-Torque lubricant rather than engine oil. The torque and tightening sequence are to be read in the instruction sheet supplied with the kit.

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
Engine block threads	Stressed at every tightening	Preserved: the stud stays in place

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:

• 2JZ-GE or 2JZ-GTE on a Dart block: higher boost pressure, or a turbo added to a naturally aspirated 2JZ-GE
• 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: 90910-02102

Why is it the most cost-effective solution?

On a 2JZ built in a Dart block, the head fasteners are the part that caps the pressure the gasket can hold. CA625+ studs with 12-point nuts push that cap back, for an outlay that bears no relation to reopening a rebuilt engine.

Consider a reinforced head gasket

To get the most out of reinforced fasteners, pair them with a head gasket that withstands the same pressure. Here is the gasket we offer for this engine: