Reinforced ARP main studs for HONDA B16 B18

The Honda engines concerned

This kit covers the 16-valve Honda B-family four-cylinders: the B16A of the Civic, CRX and Integra DA6, and the B18A1, B18B1 and B18B2 of the 1.8 Integra. ARP lists it for the B16A, the B18 and the B18 fitted with a B16 VTEC head.

On these engines the main caps are originally held by bolts (Honda part number 90006-P8A-A01); the 7/16 in studs in the kit replace them.

Reinforced ARP studs for main bearings

Each main bearing takes a share of the loads the connecting rods pass on at every combustion. Pulled downwards, the main cap tends to slide on its parting line: over time the mating faces brinell and the bearing bore loses its shape.

These 7/16 in ARP 8740 studs take the place of the original bolts. Once the block threads are cleaned, they are screwed in by hand only, then the caps are fitted. Threads, washers and nuts get ARP Ultra-Torque lubricant, as ARP advises against engine oil. Tightening is done in three equal passes, at 36, 72 then 108 Nm, in the order set by the manufacturer. Material: 8740, a chrome-moly steel that ARP specifies at 200,000 psi tensile strength, with threads rolled after heat treatment. 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 7/16 in hold up to 1,200 hp on this four-cylinder 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. If the assembly is to remain permanent, the ARP instruction sheet accepts a Loctite thread locker, with tightening carried through before the product cures.

ARP instruction sheet 208-5402 sets the nut torque at 80 ft-lb, i.e. 108 Nm, in three equal passes.

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.

Values taken from the ARP 208-5402 instruction sheet in force at the date of publication; the official instruction sheet prevails should any difference appear. Read the ARP 208-5402 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

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
Stress on the block	Bolt turns in the thread at every tightening	Stud stays still, only the nut is turned
Condition of threads	Thread tired at every removal	Thread spared
Cap fitting	Cap held by hand while screwing	Cap guided by the studs

When studs become necessary

• B16A or B18 engine built for high revs
• Power gain over the standard output
• Bottom end stripped during a rebuild
• Loose main caps or marked threads
• Racing, track or rally use

Vehicle compatibility

OEM reference: 90006-P8A-A01

Why is it the most cost-effective solution?

A B-family bottom end pushed in revs or power tires the main caps sooner than the original fasteners allowed for. These studs cost little next to the price of reworking the main bearing bores.

Consider the crankshaft main bearings

A bottom end rebuild calls for new bearings. We offer the tri-metal crankshaft main bearings that match these engines: