Reinforced ARP main studs for Nissan VG30DE VG30DETT

The Nissan engine concerned

This kit is made for the Nissan V6 of 3.0 litres, 24 valves and twin overhead camshafts, naturally aspirated (VG30DE) or twin-turbo (VG30DETT), fitted in particular to the 300ZX (Z32) in its Twin Turbo version.

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 brinell, then the bearing bore goes out of round.

This kit replaces the original main cap fasteners of the VG30DE and VG30DETT with ARP 8740 steel studs, M11 x 1.5, and their nuts. The block threads are cleaned first, then the studs are placed by hand, without tools. Once the caps are fitted, threads, nuts and washers are coated with the ARP Ultra-Torque lubricant supplied and the nuts are tightened in three equal passes, following the manufacturer's sequence. Since only the nut turns, the displayed torque matches the real preload more closely and the block thread is not subjected to torsion.

ARP makes these fasteners in 8740, a chrome-moly steel brought by heat treatment to 190,000 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. The 8740 studs in M11 x 1.5 hold up to 1,800 hp on this V6 engine (calculated estimate).

Technical specifications

Tightening torque

No torque is applied to the stud as it goes into the block: it is screwed in by hand. For a permanent installation, the instruction sheet leaves the option of a thread locker of the blue Loctite type on the block end, with the nuts fully tightened before it cures, never on the nuts and never mixed with ARP grease.

The nuts are tightened in the sequence the manufacturer specifies for the main caps; the instruction sheet supplied with the kit describes the full procedure.

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

Values taken from the ARP 102-5402 instruction sheet in force at the date of publication; the official instruction sheet prevails should any difference appear. Read the ARP 102-5402 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 driven into the block by rotation	Nuts tightened in stages, in three passes
Block thread	Subjected to the twisting of the bolt	Stud placed by hand, no strain
Fitting the caps	Cap to be held by hand when screwing	Cap positioned by the studs

When studs become necessary

• VG30DETT with raised boost pressure
• Power or engine speed far beyond the original
• 300ZX bottom end stripped for a rebuild
• Main caps that shift or tired block threads
• Repeated sporting driving, track, rally or drag

Vehicle compatibility

Why is it the most cost-effective solution?

On a VG30 pushed well beyond its original output, especially in twin-turbo form, the main caps see loads that the standard fasteners can no longer hold. ARP 8740 studs provide a much higher clamping load for a minimal extra cost compared with rebuilding a bottom end.