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4.0L / 4.6L V8 - Rover V8
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4.0L / 4.6L V8 - Rover V8
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ARP main studs and bolts in 8740 steel for the 4.0 and 4.6 L Rover V8 engines.
ARP lists these kits for the 4.0 and 4.6-litre Rover V8, eight-cylinder V engines whose crankshaft runs on five main bearings.
Originally, the main caps are held by the manufacturer's fasteners; the studs or bolts in these kits replace them, with ten fasteners for the caps (positions 1 to 10) and ten M10 x 1.5 side bolts (positions 11 to 20).
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.
Two references share this page, both in 8740 steel: the 157-5401 stud kit and the 157-5001 bolt kit. The studs take nuts; the bolts are tightened straight into the block, with washers whose chamfered face goes on the head side. The caps (positions 1 to 10) are tightened in three steps, with a final step for positions 9 and 10; the side bolts (positions 11 to 20) are tightened in one step. ARP makes these fasteners in 8740, a chrome-moly steel brought by heat treatment to 190,000 (studs) and 180,000 (bolts) 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. These 8740 studs in 1/2-13 and M10 x 1.5 take up to 2,300 hp on this eight-cylinder engine (calculated estimate). The maximum power rating of the 157-5001 bolt kit is not published by the manufacturer, so no figure is given for these bolts.
| Part number | Type | Brand | Grade / material | Head / nut | Thread |
| ARP-157-5401 | Studs | ARP | 8740 steel | Nut | 1/2-13 and M10 x 1.5 |
| ARP-157-5001 | Bolts | ARP | 8740 steel | Bolt head | 1/2-13 and M10 x 1.5 |
| Reference | Pass 1 | Pass 2 | Pass 3 | Pass 4 |
| ARP-157-5401 1/2-13 (1-8) | 34 Nm | 68 Nm | 102 Nm | |
| ARP-157-5401 1/2-13 (9-10) | 34 Nm | 68 Nm | 102 Nm | 122 Nm |
| ARP-157-5401 M10 (11-20) | 61 Nm | |||
| ARP-157-5001 1/2 (1-8) | 34 Nm | 61 Nm | 88 Nm | |
| ARP-157-5001 1/2 (9-10) | 34 Nm | 61 Nm | 88 Nm | 108 Nm |
| ARP-157-5001 M10 (11-20) | 61 Nm |
Fitting the studs: screwed into the block by hand, without a tightening tool. The ARP instruction sheet accepts a Loctite thread locker for a permanent installation, as long as tightening is finished before the product sets.
The instructions for the 157-5401 stud kit mention the ARP thread chasers 911-0005 and 912-0003 for cleaning the threads in the block before fitting.
Fitting the bolts: through the cap, straight into the block, tightened to torque in successive stages after ARP greasing of the threads and head seats.
The 157-5001 bolt kit comes with instructions that give no thread locker: do not add any on these bolts.
The nuts and bolts are tightened following the order set by the manufacturer for the caps; every step is given in the ARP instruction sheet.
Stronger fasteners change the clamping force: the size and roundness of the main bearing bores are checked after installation, and the bores are align honed if necessary, using the final fasteners and lubricant.
Torque figures taken from the ARP 157-5401 and 157-5001 instruction sheets, in the revision in force on the day of publication. In the event of any difference, the manufacturer's instruction sheets prevail. Read the ARP 157-5401 instruction sheet ; Read the ARP 157-5001 instruction sheet
Tightening is done with ARP assembly grease: the torque figures in the table were established with it, not with engine oil.
| Buy the ARP assembly grease → |
 | 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. |
| Model | Engine code | Power | Years |
| Rover V8 4.0 L | |||
| Rover V8 4.6 L |
A Rover V8 pushed beyond its stock output asks more of the crankshaft main bearings. 8740 ARP studs or bolts on the caps cost little compared with a block and a crankshaft to replace.
