Reinforced ARP main studs for Hyundai Genesis Coupé G4KF

The Hyundai engine concerned

This kit is intended for the Hyundai 2.0 L four-cylinder with engine code G4KF, as stated by ARP. It is found in the first-generation Genesis Coupé 2.0T, built from 2008 to 2014.

Reinforced ARP studs for main bearings

On a crankshaft, the main caps are what hold the shaft against the loads passed on by the connecting rods. If their clamping force drops, the cap shifts slightly on its parting line at every cycle: the mating faces brinell, then the bearing bore goes out of round.

The kit replaces the original main cap fasteners with ARP2000 studs in M10 x 1.25. Once the block threads are cleaned, each stud is screwed in by hand and the caps are set over them. Threads and nuts then receive the ARP lubricant supplied, and the nuts are tightened in three equal passes to the torque shown below.

Material: ARP2000, an alloy steel developed by ARP, rated at 220,000 psi tensile strength, with threads rolled after heat treatment. Against classes 10.9 and 12.9 of standard fasteners, between 150,800 and 176,900 psi minimum, it offers 24 to 46% more strength. On this four-cylinder engine, the ARP2000 studs in M10 x 1.25 are rated for 1,100 hp at most (calculated estimate).

Technical specifications

Tightening torque

The studs are screwed into the block by hand, with no torque. The ARP instruction sheet allows a thread locker of the blue Loctite type on the block end for a permanent installation, provided the nuts are fully tightened before it sets; never on the nuts, never with ARP grease.

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

With stronger fasteners, the clamping force is no longer what it was originally: the size and roundness of the main bearing bores must be checked once installation is complete, and align honed if necessary with the final fasteners and lubricant.

The torque figures above come from the ARP 228-5401 instruction sheet, revision applicable at publication. The official instruction sheet is authoritative in the event of any difference. Read the ARP 228-5401 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

Coming from the aerospace industry, Gary Holzapfel founded ARP (Automotive Racing Products) in the early 1970s to put an end to engine failures caused by weak fasteners in motorsport. The company designs and manufactures thousands of part numbers in California, in several material grades depending on the application.

Advantages over the original bolts

Criterion	Original main bolts	ARP studs
Tightening	The bolt turns in the block under torque	Only the nut turns, in three passes
Block thread	Worked by the bolt turning at every assembly	Stud placed by hand, no strain
Fitting the caps	Cap held by hand while the bolt goes in	Cap centred by the studs

When studs become necessary

• Forced induction added, or boost pressure increased
• Higher maximum engine speed or longer crankshaft stroke
• Bottom end rebuild, where the original fasteners have to be replaced anyway
• Signs of cap walk or tired block threads
• Racing use, with repeated load cycles

Vehicle compatibility

Why is it the most cost-effective solution?

On a G4KF pushed beyond standard output, the main caps see loads the original fasteners were not designed to hold. These ARP2000 studs make the clamping steadier for a cost out of proportion with a crankshaft or a block to repair.