Reinforced ARP cylinder head studs HONDA B16

The engines concerned

This kit fits the 16-valve inline four-cylinder 1.6-litre VTEC Honda B16A engine, in its B16A1, B16A2 and B16A3 versions, fitted notably to the Civic VTi (EG6, EK4), the CRX VTi (EG2) and the Integra (DA6).

As standard, the cylinder head is held by ten Honda head bolts (reference 90006-PG6-003), tightened in two passes to 29 then 83 Nm, in the manufacturer's tightening order. Every refit loads these bolts in the block thread again.

Reinforced ARP cylinder head studs

The job of the head fasteners is to keep the cylinder head locked to the block despite the pressure inside the combustion chambers. They keep the gasket compressed; as soon as their clamping force drops, leaks appear between head and block.

Kit ARP 208-4601 combines 8740 studs with a 7/16 in thread and 12-point nuts. According to the instruction sheet, the block threads are cleaned, the studs screwed in by hand and the head fitted, then threads, nuts and washers are coated with the ARP Ultra-Torque lubricant supplied before tightening in three equal passes, in the manufacturer's order. 8740 is a chrome-molybdenum steel, rated by ARP at 200,000 psi tensile strength. As a reference point, an engine's standard fasteners mostly belong to property classes 10.9 and 12.9, with a minimum tensile strength between 150,800 and 176,900 psi. In 7/16 in, the 8740 studs hold up to 600 hp on this four-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

The studs are fitted into the block by hand, without a torque wrench. For a permanent installation, the instruction sheet accepts thread locker, with tightening to be completed before it sets.

The block threads can be run through again with the ARP thread chaser; the sheet provides for this when needed.

When the studs reach the water jacket, the sheet asks for ARP thread sealer on the block-side threads.

Tightening to torque is done in three steps, in the order set by the engine manufacturer, with ARP lubricant applied to the threads and under the nuts, a condition for the table values to apply.

The instruction sheet also calls for ARP lubricant on the washers.

Source of these values: ARP instruction sheet 208-4601, revision current at the time of publication. The official instruction sheet applies if any discrepancy appears; it covers the entire procedure and the tightening sequence. Read the ARP 208-4601 instruction sheet

Technical guide

All torque values on this page are given with ARP assembly grease on the threads and under the nuts; another lubricant would make them wrong.

The ARP brand

ARP (Automotive Racing Products) was born in the early 1970s from the initiative of Gary Holzapfel, an engineer from the aerospace industry, determined to eliminate engine failures caused by weak fasteners in motorsport. The company designs and manufactures thousands of parts in California, in several material grades suited to each use.

Advantages over the original bolts

Criterion	Original head bolts	Reinforced ARP studs
Tightening method	29 then 83 Nm	Three equal torque passes
Block thread	Works at every fitting	Preserved: studs screwed in by hand

When studs become necessary

The original fasteners are sized for the engine as it leaves the factory. They need to be reinforced when:

• B16A, B16A1, B16A2 and B16A3: power exceeds stock output, in a strongly tuned naturally aspirated or a boosted build
• The compression ratio rises as the build progresses
• The original gasket is replaced by a reinforced MLS gasket, which requires a high and uniform preload
• The engine has already suffered a lifted head or a gasket leak
• Competition use imposes severe heat cycles and regular head removals

Vehicle compatibility

OEM reference: 90006-PG6-003

Why is it the most cost-effective solution?

On a tuned B16A, the original bolts are the first to give way once cylinder pressure climbs, and the gasket follows. Fitting a kit of ARP 8740 studs costs far less than repairing a cylinder head, gasket and labour included.

Consider a reinforced head gasket

Reinforced fasteners are only fully worthwhile with a head gasket able to resist the same pressure. We offer the following part for this engine: