Reinforced ARP bolts for OEM rods Opel Vauxhall 1.6 16V 8V X16XE X16XEL C16NZ

The Opel and Vauxhall 1.6 engines concerned

This kit is for the 1.6-litre Opel and Vauxhall engine of 1,598 cc (79 mm bore, 81.5 mm stroke), offered in a 16-valve version (X16XE and X16XEL, 100 to 106 hp) and an 8-valve version (C16NZ, about 75 hp). It is found under the bonnet of the Corsa B, for the X16XE, and of the Astra F, for the X16XEL and the C16NZ.

Whether it stays in light tuning or gets a more radical camshaft, this four-cylinder asks more of its rods: inertia loads rise with engine speed, and the rod bolts are what hold them. The kit replaces the original bolts with ARP bolts in 8740.

Reinforced ARP bolts for connecting rods

At every engine revolution, the rod and piston assembly pulls on the rod cap, and only its bolts hold it against these inertia loads. The original ones are intended for stock power and for a single installation.

The original rod bolts are replaced by ARP bolts in 8740, thread size M8. ARP recommends tightening them by measuring their stretch; without a gauge, refer to the torque given in the instruction sheet. Material: 8740, a chrome-moly steel heat treated by ARP to 180,000 psi tensile strength, with threads rolled after heat treatment. Factory-fitted fasteners usually fall into classes 10.9 and 12.9, between 150,800 and 176,900 psi minimum. The 8740 bolts hold up to 8,750 rpm (calculated estimate).

Technical specifications

Tightening torque and stretch

For this part, ARP favours stretch measurement in addition to torque, the key to an exact preload. The figures in the table assume ARP lubricant.

Source of the torque and stretch figures: ARP 109-6002 instruction sheet, in the revision applicable at publication. The manufacturer's instruction sheet prevails in the event of any difference. Read the ARP 109-6002 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.

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

All the torque and stretch values on this page assume ARP assembly grease on the threads and under the bolt head; engine oil does not replace it.

The ARP brand

An engineer with an aerospace background, Gary Holzapfel launched ARP (Automotive Racing Products) in the early 1970s with one goal: to eliminate engine failures caused by weak fasteners in racing. ARP designs and manufactures thousands of part numbers in California, cylinder head, main and rod bolts, in several materials depending on the use, and has become known for the consistency of its manufacturing.

Vehicle compatibility

Why is it the most cost-effective solution?

On an X16XE or a C16NZ, a rod bolt that gives way takes the rod, the piston and the block with it. ARP bolts in 8740 withstand higher engine speeds and inertia loads than the original bolts and lower that risk, at a cost far below that of rebuilding the bottom end.

Why not step up to forged connecting rods?

A forged connecting rod starts as a steel billet, usually 4340, shaped hot under very high pressure: its material is denser and more homogeneous than that of a stock rod. Compared with an original rod, often made of sintered metal and designed for cost, a 4340 forged rod offers about +19% yield strength, +8% tensile strength and +19 to +37% fatigue strength. It is the foundation of a reliable high-power build. For your engine: