Reinforced ARP main studs for NISSAN SR20

The Nissan engines concerned

This kit is made for the Nissan inline four-cylinder of 2.0 litres and 16 valves, naturally aspirated or turbo (codes SR20DE, SR20DET, SR20VE and SR20VET), fitted in particular to the 200SX S14 and Silvia S15.

This engine leaves the factory with main cap bolts; the ARP kit replaces them with studs.

Reinforced ARP studs for main bearings

On a crankshaft, the main caps are what hold the shaft against the loads passed on by the connecting rods. If their clamping force drops, the cap shifts slightly on its parting line at every cycle: the mating faces become indented, then the bearing bore goes out of round.

This kit replaces the original main cap fasteners with ARP M11 studs in 8740 steel and their nuts. Each stud is screwed into the block by hand; once the caps are in place, the ARP Ultra-Torque lubricant provided is applied to the threads, nuts and washers, and the nuts are brought to torque in three passes, following the manufacturer's sequence. Preload gains in both level and consistency, and the block threads are no longer dragged round by a turning bolt. Material: 8740, a chrome-moly steel that ARP specifies at 190,000 psi tensile strength. Factory-fitted fasteners usually belong to classes 10.9 and 12.9, with 150,800 to 176,900 psi minimum tensile strength. The 8740 studs in M11 x 1.5 hold up to 1,200 hp on this four-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

Fitting the studs: screwed into the block by hand, without a tightening tool. The ARP instruction sheet accepts a Loctite thread locker for a permanent installation, as long as tightening is finished before the product sets.

This instruction sheet was revised for insufficient clearance between the upper oil pan and the studs on rear-wheel-drive cars: the clearance is checked before the pan is fitted, the pan must sit flat on the block rail.

The nuts are tightened following the order set by the manufacturer for the caps; every step is given in the ARP instruction sheet.

Moving to reinforced fasteners changes the clamping force on the caps. After installation, the size and roundness of the bores are checked, then the bores are line-honed if needed, always with the final fasteners and lubricant.

Torque figures taken from the ARP 202-5402 instruction sheet, in the revision in force on the day of publication. In the event of any difference, the manufacturer's instruction sheet prevails. Read the ARP 202-5402 instruction sheet

Technical guide

Tightening is done with ARP assembly grease: the torque figures in the table were established with it, not with engine oil.

The ARP brand

ARP, short for Automotive Racing Products, was born in the early 1970s on the initiative of Gary Holzapfel, an engineer from the aerospace sector, in response to the engine failures caused in racing by inadequate fasteners. Today the brand produces thousands of part numbers in California, offered in several materials depending on the application.

Advantages over the original bolts

Criterion	Original main bolts	Reinforced 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

• Forced induction added, or boost pressure increased
• Higher maximum engine speed or longer crankshaft stroke
• Bottom end rebuild
• Signs of cap walk or tired block threads
• Racing use, with repeated load cycles

Vehicle compatibility

Why is it the most cost-effective solution?

On an SR20 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. Their cost weighs little beside a crankshaft and a block to be rebuilt.

Consider the crankshaft main bearings

To complete the bottom end overhaul, consider the tri-metal crankshaft main bearings suited to these engines: