Reinforced ARP bolts and nuts for OEM rods HONDA ACURA C30A C30A3 C30A4

The Honda C30A engine concerned

This kit is designed for the Honda C30A, a 3.0-litre petrol V6 (2,977 cc, 90 mm bore, 78 mm stroke, 24-valve VTEC) fitted to the first-generation Honda and Acura NSX built from 1990 to 2005.

It replaces the original rod bolt: ARP lists it as a bolt and nut set for the Acura 3.0L (C30A) V6 NSX, with the bolts pressed into the connecting rods.

Reinforced ARP bolts and nuts for connecting rods

At every revolution, the rod bolt takes the pull of the rod and piston assembly, which tries to force the cap away through inertia. As original equipment, it is sized for stock power.

Supplied in ARP2000 and fitted in two stages: the bolts are pressed in, then the nuts are tightened as the ARP instruction sheet directs, preferably by stretch, or to 50.2 Nm without a gauge. Material: ARP2000, an alloy steel developed by ARP, heat treated to 220,000 psi tensile strength, with threads rolled after heat treatment. Against classes 10.9 and 12.9 of original fasteners, between 150,800 and 176,900 psi minimum, the margin is 24 to 46%. The engine speed allowed by the ARP2000 bolts goes up to 10,250 rpm (calculated estimate).

Technical specifications

The ARP instruction sheet specifies that the rod bore needs a generous chamfer so that the radius under the bolt head does not bear on the edge.

Tightening torque and stretch

ARP recommends tightening to a measured stretch, which gives a more accurate preload than torque alone, given as a fallback. Torque and stretch figures assume ARP lubricant.

The values above come from the ARP 208-6004 instruction sheet applicable at the date of publication; it is authoritative in the event of any difference. Read the ARP 208-6004 instruction sheet

Assembly is done without thread locker, as the ARP instruction sheet calls for none: ARP Ultra-Torque grease is applied to the threads of each bolt and to the bearing face of its nut.

Once the fasteners are fitted, the ARP instructions call for the big ends to be checked and resized by a machine shop.

Measuring bolt stretch

Tightening to stretch means setting the preload on how much the bolt actually stretches, rather than on a torque affected by friction. With the bolt fitted, the dial gauge is placed on both its ends and the bolt is tightened until the stretch given in the table is read. It is the safest method on a highly tuned engine.

Technical guide

Torque and stretch figures are only valid with ARP assembly grease, applied to the bolt threads and to the bearing face of the nuts.

The ARP brand

ARP (Automotive Racing Products) came into being in the early 1970s, when Gary Holzapfel, who came from the aerospace industry, decided to tackle the engine failures caused in motorsport by inadequate fasteners. Today the brand produces thousands of part numbers in California for the cylinder head, the main bearings and the connecting rods, in materials suited to each application, with manufacturing known for its consistency.

Vehicle compatibility

Why is it the most cost-effective solution?

A C30A V6 that is revved hard, especially once modified, asks a lot of its rod bolts in tension. A single failure can wreck the rod, the piston and the crankcase; an ARP2000 kit costs far less than a rebuilt engine.