Reinforced ARP bolts for OEM rods ROVER MG LOTUS LAND ROVER CATERHAM WESTFIELD 11K4F 14K4F 16K4F 18K4F 18K4G 18K4K

The Rover K-Series engines concerned

This kit covers the Rover K-Series family, four-cylinder 16-valve engines from 1.1 to 1.8 litres: the 11K4F, 14K4F, 16K4F and 18K4F, plus the 18K4G and 18K4K, found notably on the Lotus Elise, the VVC versions and the turbo versions. They sit under the bonnet of the Rover 100, 200, 25, 400, 45, 75 and Coupé, the MG F, TF, ZR, ZS and ZT, the Lotus Elise and the Land Rover Freelander. ARP describes the application of this part number as “Rover K-Series” with an M8 thread. This kit also fits the Caterham Seven and 21, the Westfield Seven, the FSO Polonez, the Minelli TF, the MG 6, 550 and 7, and the Chinese Roewe, Hawtai, Fengxing and Yema models.

On each of these engines, the original rod bolt gives way to an ARP bolt in ARP2000 with an M8 thread, a 12-point head and no washer, screwed into the standard rod.

Reinforced ARP bolts 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 and is replaced at every strip-down.

ARP gives tightening to a measured stretch as the reference method; without a gauge, the instruction sheet sets a torque of 41 Nm. 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%. The ARP2000 bolts hold up to 9,500 rpm (calculated estimate).

Technical specifications

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.

Figures taken from the ARP 206-6007 instruction sheet, revision in force on the day of publication. Should any difference appear, the official instruction sheet takes precedence. Read the ARP 206-6007 instruction sheet

The ARP instruction sheet does not require a thread locker for this kit; only ARP Ultra-Torque grease is applied, on the threads as well as under the bolt head.

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

With the stretch gauge, you read directly how much the bolt stretches during tightening: the dial gauge sits on both ends of the fitted bolt, and tightening stops when the stretch reaches the value in the table. Friction no longer comes into play, hence a more consistent preload on a heavily stressed engine.

Technical guide

Torque and stretch figures are only valid with ARP assembly grease, applied to the threads and under the head.

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

Why is it the most cost-effective solution?

As soon as these Rover four-cylinders rev higher, every rod bolt sees a growing tensile load: if one breaks, the rod, the piston and the block pay for it. Bolts in ARP2000 cost a fraction of a bottom-end rebuild.