Reinforced ARP main studs for BMW Toyota B58B30

The engine concerned

The B58B30 is BMW's 3.0-litre turbocharged inline six-cylinder petrol engine (2,998 cm³, 82 mm bore, 94.6 mm stroke), in production since 2015. It powers many BMW models, from the M140i to the 7 and 8 Series, including the X3, X4, X5, X6, X7 and Z4, as well as the Toyota GR Supra from 2019.

As standard, the crankshaft is held by 14 main cap bolts (reference 11 11 8 604 584, M10 x 85 bolts, class 11.9).

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.

This kit replaces the original bolts with 14 ARP2000 studs, with their nuts and washers as the ARP instruction sheet lists them. On the B58, each stud is installed by hand; once the caps are back in place, washers and threads are lubricated with assembly lubricant, then the nuts are tightened to torque in three passes. Clamping load rises and becomes more even, and the block threads no longer take the turning of a bolt. Two part numbers cover this engine: ARP-201-5402 for the BMW models and ARP-203-5409 for the Toyota GR Supra; their instruction sheets give the same torque values and the same number of nuts. ARP2000 is an alloy steel developed by ARP and heat treated to 220,000 psi tensile strength, with threads rolled after heat treatment. Standard engine fasteners commonly belong to property classes 10.9 and 12.9, i.e. 150,800 to 176,900 psi minimum tensile strength: ARP2000 therefore sits 24 to 46% above that. The ARP2000 studs in M10 x 1.5 hold up to 1,400 hp on this six-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

Fitting the studs: screwed into the block by hand, without a tightening tool. The ARP instruction sheet provides for no thread locker.

The nuts are tightened following the order set by the manufacturer for the caps; every step is given in the ARP instruction sheet.

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.

Torque figures taken from the ARP 201-5402 and 203-5409 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 201-5402 instruction sheet ; Read the ARP 203-5409 instruction sheet

Technical guide

Tightening is done with ARP assembly grease: the torque figures in the table were established with it, not with engine oil.

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
Tightening	Bolt screwed straight into the block	Three torque passes, steady build-up
Threads in the block	Loaded by the turning bolt at every tightening	Stud screwed in by hand, no torque
Refitting the caps	Cap held by hand while the bolts go in	Cap guided by the two studs

When studs become necessary

• Forced induction added, or boost pressure increased
• Higher maximum engine speed or longer crankshaft stroke
• Bottom end rebuild
• Signs of cap walk or tired block threads
• Racing use, with repeated load cycles

Vehicle compatibility

OEM reference: 11 11 8 604 584

Why is it the most cost-effective solution?

ARP2000 studs hold the main caps more firmly than the original bolts, which lowers the risk of bottom-end failure on a tuned engine. Fitting them costs little next to rebuilding a damaged crankshaft and block.

Consider the crankshaft main bearings

To complete the bottom end overhaul, consider the tri-metal crankshaft main bearings suited to these engines: