Reinforced ARP bolts and nuts for OEM rods TOYOTA 4A-GE

The Toyota 4A-GE engine concerned

This kit is intended for the Toyota 4A-GE 1.6-litre engine (1,587 cc), a four-cylinder with twin overhead camshafts, sold in 16-valve form (AE86, AE92, MR2 AW11) and in 20-valve form (Silver Top and Black Top); ARP also lists the single-cam 4A-LC.

It replaces the original rod bolt, tightened with a nut, with an ARP 8740 bolt of M9 diameter that is pressed into the connecting rod.

Reinforced ARP bolts and nuts for connecting rods

Few parts of the bottom end work as hard as the rod bolt: at every revolution, it is what stops the cap from pulling away under the inertia loads of the rod and piston assembly. The original bolt is designed for stock power.

The bolts in this kit are pressed into the rods and take a nut; ARP recommends tightening them while checking stretch with a gauge. These bolts are made from 8740, a chrome-moly steel brought to 180,000 psi tensile strength by ARP's heat treatment; the threads are rolled afterwards. For comparison, classes 10.9 and 12.9 of original fasteners have a minimum of 150,800 to 176,900 psi. The 8740 bolts hold up to 9,500 rpm (calculated estimate).

Technical specifications

The ARP instructions call for a sufficient chamfer at the top of the rod bore to clear the radius under the bolt head before the bolts are pressed in.

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.

The values above come from the ARP 203-6001 instruction sheet applicable at the date of publication; it is authoritative in the event of any difference. Read the ARP 203-6001 instruction sheet

The ARP instructions mention no thread locker for this kit.

According to the ARP instructions, the big ends must be checked and resized with the fasteners in place; plan a visit to 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 bolt threads and to the bearing face of the nuts.

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?

On a 4A-GE built to rev high, the rod bolts carry inertia loads that climb with engine speed, and a single bolt letting go wrecks the rod, the piston and the block. ARP 8740 bolts secure this point for a cost out of all proportion to that of rebuilding an engine.

Matching connecting rod bearings

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