Reinforced ARP bolts and nuts for OEM rods SUBARU SAAB EJ20 EJ25

The Subaru and Saab engines concerned

This kit is intended for the Subaru EJ-family flat-fours: the 1.8-litre EJ18, the turbocharged 2.0-litre EJ20, with its EJ205 and EJ207 versions fitted to the Impreza WRX and WRX STi, the 2.2-litre EJ22 and the naturally aspirated 2.5-litre EJ25, found in the Impreza, Legacy, Forester, Outback and Saab 9-2X. The ARP instructions cover the EJ18 to EJ25 non-turbo engines and the turbocharged EJ20.

This ARP kit replaces the original rod bolt, reference 12109AA062, tightened with a nut, with an ARP2000 bolt that is pressed into the connecting rod.

Reinforced ARP bolts and nuts for connecting rods

At every revolution, the rod bolt takes the pull of the rod and piston assembly, which tries to force the cap away through inertia. As original equipment, it is sized for stock power.

The bolts in this kit are made of ARP2000; they are pressed into the rod before the caps are fitted, and each nut is best tightened to a measured stretch, ARP giving a torque of 56.9 Nm for anyone without a gauge. Material: ARP2000, an alloy steel developed by ARP, heat treated to 220,000 psi tensile strength, with threads rolled after heat treatment. Against classes 10.9 and 12.9 of original fasteners, between 150,800 and 176,900 psi minimum, the margin is 24 to 46%.

Technical specifications

According to the ARP instructions, the bolts are pressed into the rods before the rod caps are fitted.

Tightening torque and stretch

ARP recommends tightening to a measured stretch, which gives a more accurate preload than torque alone, given as a fallback. Torque and stretch figures assume ARP lubricant.

Source of the torque and stretch figures: ARP 260-6301 instruction sheet, in the revision applicable at publication. The manufacturer's instruction sheet prevails in the event of any difference. Read the ARP 260-6301 instruction sheet

No thread locker is called for by the ARP instruction sheet for this kit: the bolts are fitted with ARP Ultra-Torque grease, on their threads and on the bearing face of the nuts.

Once the fasteners are fitted, the ARP instructions call for the big ends to be checked and resized by a machine shop.

Measuring bolt stretch

Stretch measurement supplements torque tightening and gives the most accurate preload. It is done with the bolt in place: the gauge, fitted with a dial indicator, bears on both ends of the bolt and shows the stretch achieved, to be brought to the value in the table above. This avoids the variations caused by friction, which matters on a highly stressed engine.

Technical guide

Tightening is done with ARP assembly grease, on the bolt threads and on the bearing face of the nuts: the torque and stretch figures in the table were established with it.

The ARP brand

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace sector, ARP (Automotive Racing Products) was born to put an end to fastener-related engine failures in racing. Its thousands of part numbers, designed and manufactured in California for the cylinder head, the main bearings and the connecting rods, come in several materials depending on the application and are recognised for the consistency of their manufacture.

Vehicle compatibility

OEM reference (rod bolt): 12109AA062

Why is it the most cost-effective solution?

On a turbocharged EJ20, an EJ205 or an EJ207 run at a higher boost pressure, or on a naturally aspirated EJ22 or EJ25 that is revved harder, the rod bolts see tensile loads that grow with engine speed, and one bolt that breaks destroys the rod, the piston and the block. Fitting ARP2000 bolts costs a small fraction of what a full bottom-end rebuild would.

Matching connecting rod bearings

Removing the connecting rods is the right time to replace their bearings: here are the ones that fit this engine.