Reinforced ARP main studs for Honda and Acura B17A B18

The Honda and Acura engines concerned

This kit is for the 16-valve Honda and Acura B-family four-cylinders, from the B17A to the B18C5, according to the applications published by ARP and RWB. It covers the Integra DA9 and DC2 in their B17A1, B18A1, B18B1, B18C1 and B18C5 versions.

On the B18, the main caps originally take bolts (Honda part number 90006-P8A-A01); the 7/16 in studs in this kit take their place.

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.

The 7/16 in ARP 8740 studs in this kit replace the original main bolts. The block threads are cleaned, the studs are screwed in by hand only, then the caps are put in place. Threads, washers and nuts receive ARP Ultra-Torque lubricant; tightening then takes place in three equal passes, to 36, 72 then 108 Nm, following the manufacturer's sequence. ARP excludes engine oil, as its friction skews the tightening. 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. On this four-cylinder engine, the 8740 studs in 7/16 in are rated for 1,200 hp at most (calculated estimate).

Technical specifications

Tightening torque

Fitting the studs: screwed into the block by hand, without a tightening tool. Where a permanent installation is wanted, ARP accepts a thread locker of the blue Loctite type on the block-side thread, provided the nuts are tightened before it sets; none goes on the nuts or with ARP grease.

According to ARP instruction sheet 208-5403, the nuts are tightened in three equal passes up to 80 ft-lb, i.e. 108 Nm.

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

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.

The torque figures above come from the ARP 208-5403 instruction sheet, revision applicable at publication. The official instruction sheet is authoritative in the event of any difference. Read the ARP 208-5403 instruction sheet

Technical guide

All the torque values on this page assume ARP assembly grease; with engine oil they are no longer correct.

The ARP brand

Coming from the aerospace industry, Gary Holzapfel founded ARP (Automotive Racing Products) in the early 1970s to put an end to engine failures caused by weak fasteners in motorsport. The company designs and manufactures thousands of part numbers in California, in several material grades depending on the application.

Advantages over the original bolts

Criterion	Original main bolts	Reinforced ARP studs
Load on the block	The bolt transmits its rotation to the thread at every tightening	The stud does not turn, only the nut turns
Thread upkeep	Thread that wears screwing after screwing	Thread preserved, stud placed by hand
Cap positioning	Cap to be steadied while screwing	Cap centred by the studs

When studs become necessary

• B-family engine built to rev higher
• Power above the original output
• Bottom end opened for an overhaul
• Main caps that shift or damaged block threads
• Sports use, track or event

Vehicle compatibility

OEM reference: 90006-P8A-A01 (B18)

Why is it the most cost-effective solution?

A B-family engine pushed for revs or power loads the main caps more than the standard fasteners were meant to bear. These ARP studs give a more even clamp for a modest outlay compared with a block rework.

Consider the crankshaft main bearings

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