Reinforced ARP main studs for Nissan KA24E KA24DE

The Nissan engines concerned

This kit is made for the Nissan inline four-cylinder of 2.4 litres, with a single overhead camshaft (KA24E) or double overhead camshafts (KA24DE), fitted in particular to the 240SX, Altima, Bluebird and Navara pick-up.

Reinforced ARP studs for main bearings

The bottom end rests on its main bearings: combustion after combustion, the loads coming from the connecting rods end up on them. Under this stress the main cap tries to move on its parting line, which eventually brinells the mating faces and distorts the bearing bore.

This kit replaces the original main cap fasteners with ARP M10 studs in 8740 steel and their nuts. The studs are screwed into the block by hand, then the caps are fitted. Threads, nuts and washers receive the ARP Ultra-Torque lubricant provided, and the nuts are torqued in three passes, in the manufacturer's sequence. Preload builds more evenly, and the block threads are no longer stressed by a turning bolt.

ARP makes these fasteners in 8740, a chrome-moly steel brought by heat treatment to 200,000 psi tensile strength; the threads are rolled once the treatment is complete. As a reference point, an engine's original fasteners generally fall into classes 10.9 and 12.9, whose minimum ranges from 150,800 to 176,900 psi. These 8740 studs in M10 take up to 1,000 hp on this four-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

The studs are screwed into the block by hand, with no torque. The ARP instruction sheet allows a thread locker of the blue Loctite type on the block end for a permanent installation, provided the nuts are fully tightened before it sets; never on the nuts, never with ARP grease.

Follow the cap tightening sequence recommended by the manufacturer when bringing the nuts up to torque; the kit's instruction sheet details each step.

With stronger fasteners, the clamping force is no longer what it was originally: the size and roundness of the main bearing bores must be checked once installation is complete, and align honed if necessary with the final fasteners and lubricant.

Values taken from the ARP 102-5401 instruction sheet in force at the date of publication; the official instruction sheet prevails should any difference appear. Read the ARP 102-5401 instruction sheet

Technical guide

The torque figures given only apply with ARP assembly grease, never with engine oil.

The ARP brand

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace industry, ARP (Automotive Racing Products) set out to prevent fastener-related engine failures in motorsport. Its thousands of part numbers are designed and manufactured in California, in materials chosen for each use.

Advantages over the original bolts

Criterion	Original main bolts	ARP studs
Tightening method	Bolt turned into the block	Nuts tightened progressively, in three passes
Block thread	Loaded by the turning bolt	Stud placed by hand, no torque load
Refitting the caps	Cap to be held while screwing	Cap positioned by the studs

When studs become necessary

• Turbocharged or supercharged engine, or boost raised beyond stock
• Build that increases engine speed or stroke
• Bottom end overhaul
• Caps that have moved or marked block threads
• Track or rally use with repeated loads

Vehicle compatibility

Why is it the most cost-effective solution?

On a KA24 tuned well beyond its original output, ARP 8740 steel studs, stronger than the original fasteners, clamp the main caps more firmly and reduce the risk of bottom-end failure. The extra cost stays small compared with repairing a crankshaft and a block.