Reinforced ARP main studs for HONDA C30 C32

The Honda engines concerned

This kit is for the naturally aspirated V6 engines of the first-generation Honda and Acura NSX: the 3.0-litre C30A and the 3.2-litre C32B, both 24-valve VTEC, built from 1990 to 2005. ARP lists part number 208-5801 for the 3.0 and 3.2-litre NSX of that period.

On the NSX, ordinary screws fitted at the factory hold the bearing caps; this kit puts studs in their place.

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 ARP2000 studs to be tightened with 12-point nuts. Fitting and tightening follow the ARP instruction sheet for the kit. These fasteners are made from ARP2000, an ARP-specific alloy steel that reaches 220,000 psi tensile strength after heat treatment. Compared with classes 10.9 and 12.9 of the original fasteners, from 150,800 to 176,900 psi minimum tensile strength, the margin ranges from 24 to 46%. This solution suits an NSX whose bottom end is stressed harder than it was originally.

Technical specifications

Tightening torque

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

Technical guide

For assembly, use the ARP assembly grease intended for the purpose rather than 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	Reinforced ARP studs
Fastening principle	Fasteners screwed straight into the block	Studs fixed in the block, nuts tightened onto them
Block threads	Stressed at every removal	Less stressed as long as the studs stay in place
Caps during assembly	Caps to be held while screwing	Caps guided by the studs

When studs become necessary

• NSX built for road or track
• Power raised noticeably above the original
• Crankshaft removed to check the bearing seats
• Main caps to be made more reliable before competition

Vehicle compatibility

Why is it the most cost-effective solution?

An NSX V6 used on the road or on track, with raised power, asks more of its main caps than the original engine does. Securing them with ARP2000 studs protects the crankshaft and the block, at a cost well below that of reconditioning the bottom end.