Reinforced ARP cylinder head studs HONDA B20B

The engine concerned

ARP lists this kit for Honda's B20B block, an inline four-cylinder of 1,973 cc (84 mm bore, 89 mm stroke) combined with a B16A cylinder head. As original equipment, the B20B powers the first-generation Honda CR-V.

In this build, the studs of ARP kit 208-4306 take the place of the original head bolts.

Reinforced ARP cylinder head studs

Cylinder head fasteners work constantly: they hold the head tight against the block, crush the gasket to the right value and hold back the push of the gases at every combustion. If they lose even a little tension, the gasket starts to leak.

For this combination ARP offers a single part number: the 208-4306, in 8740, with 12-point nuts and a 7/16 in thread. The instruction sheet has you screw the studs into the block by hand first, fit the cylinder head, then tighten the nuts and washers, lubricated with the ARP Ultra-Torque supplied, 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

No torque is applied to the studs as they go into the block: they are screwed in by hand. The instruction sheet leaves the option of thread locker to mount them permanently, provided tightening is done before the product hardens.

According to the sheet, all the block threads are cleaned before assembly and, if needed, chased with the ARP tool made for the job.

Where the studs reach the water jacket, the sheet says to coat their block-side threads with ARP thread sealer.

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.

The torque figures above come from ARP instruction sheet 208-4306, revision applicable on the day the page went online. The official instruction sheet prevails in case of difference and describes the complete procedure, tightening sequence included. Read the ARP 208-4306 instruction sheet

Technical guide

The stated tightening torques only make sense with ARP assembly grease, applied to the threads and under the nuts.

ARP undercut studs

An undercut stud has a reduced-diameter shank. This profile, ARP explains, spreads stretch more evenly across the studs: the cylinder head is clamped with a steadier force, gasket compression is better compensated and the gasket is less likely to fail.

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
Block threads	Stressed at every tightening	Spared (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:

• B20B built for fast road or track use (B16A head, raised compression, high engine speed)
• 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

Why is it the most cost-effective solution?

The standard fasteners of a B20B are sized for the original output: as soon as a build raises combustion pressure, they are what limits how well the gasket holds. A kit of ARP 8740 studs keeps the head pressed down with a higher clamping load, for far less than redoing a cylinder head, gasket and labour included.