Reinforced ARP main studs for VOLVO B5254 (1999 and earlier)

The Volvo B5254 engine

This kit covers the Volvo B5254, a 20-valve inline five-cylinder of 2,435 cc (2.5L in the ARP catalogue), in the ARP application for engines from 1999 and earlier. ARP sets it apart from the kit for engines from 2000 onwards.

The original Volvo fasteners hold the main caps and the intermediate section; the kit's studs, in three different diameters, 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 become indented and the bearing bore loses its shape.

The kit has 29 ARP2000 studs: 12 in M10 x 1.5 (positions 1 to 12), 12 in M8 x 1.25 (13 to 24) and 5 in M7 (25 to 29), intended for the main caps and the intermediate section of the B5254. After cleaning the block and chasing the threads with the ARP taps if needed, the M10 studs are screwed in by hand only, then the M8 and M7 studs are fitted by their hexagonal socket. Washers and nuts are coated with ARP Ultra-Torque, the instructions ruling out engine oil. These fasteners are made from ARP2000, an ARP-specific alloy steel that reaches 220,000 psi tensile strength after heat treatment. Compared with classes 10.9 and 12.9 of the original fasteners, from 150,800 to 176,900 psi minimum tensile strength, the margin ranges from 24 to 46%. The ARP2000 studs in M10 x 1.5 / M8 x 1.25 / M7 hold up to 1,300 hp on this five-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

The studs are screwed into the block by hand, with no torque. According to the ARP instruction sheet, a Loctite thread locker may be used to fix the studs permanently.

The M8 and M7 studs go in through the hexagonal socket at their end. The manufacturer's sequence is as follows: M10 at 41 Nm (30 ft-lb), M8 at 34 Nm (25 ft-lb), M7 at 20 Nm (15 ft-lb), then the M10 studs take a second pass at 88 Nm (65 ft-lb).

The nuts are tightened in the sequence the manufacturer specifies for the main caps; the instruction sheet supplied with the kit describes the full procedure.

Moving to reinforced fasteners changes the clamping force on the caps. After installation, the size and roundness of the bores are checked, then the bores are line-honed if needed, always with the final fasteners and lubricant.

Values taken from the ARP 219-5802 instruction sheet in force at the date of publication; the official instruction sheet prevails should any difference appear. Read the ARP 219-5802 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

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace industry, ARP (Automotive Racing Products) set out to prevent fastener-related engine failures in motorsport. Its thousands of part numbers are designed and manufactured in California, in materials chosen for each use.

Advantages over the original bolts

Criterion	Original main bolts	Reinforced ARP studs
Tightening	Bolt turning in the block at every tightening step	Only the nuts turn, studs fixed in the block
Repeated refits	Block threads worn down rebuild after rebuild	Studs fitted once, block threads kept intact
Locating the caps	Cap to hold in place until the first threads engage	Cap slid onto the studs, already in position

When studs become necessary

• Pre-2000 five-cylinder Volvo B5254 pushed on the track or in rally
• Engine loaded far beyond what the series intended
• Block opened to rework the whole crankshaft and its bearings
• Marked threads or caps that loosen under load
• Reconstruction with a new forged crankshaft, rods or pistons

Vehicle compatibility

Why is it the most cost-effective solution?

On a pre-2000 B5254 prepared for competition, the main caps work far harder than originally planned. This kit holds them more securely and so spares you the cost of a damaged crankshaft or block.