ARP reinforced crankshaft main studs for Toyota 3S-GE 3S-GTE

The Toyota engines concerned

The 3S is Toyota's 2.0-litre inline four-cylinder petrol engine (1,998 cm³, 86 mm bore, 86 mm stroke), built from 1986 to 2007 as the naturally aspirated 3S-GE and the turbocharged 3S-GTE. It powers the Toyota Celica, MR2, Caldina and Carina, among others.

The crankshaft is held in place by the original main cap bolts, which this kit replaces with studs.

Reinforced ARP studs for main bearings

The bottom end rests on its main bearings: combustion after combustion, the loads coming from the connecting rods end up on them. Under this stress the main cap tries to move on its parting line, which eventually brinells the mating faces and distorts the bearing bore.

This kit replaces the original main cap bolts with ARP 8740 steel studs, with their nuts and washers as the ARP instruction sheet lists them. On the 3S block, each stud goes in by hand, the caps are refitted, washers and threads are coated with ARP assembly lubricant, and the nuts are brought up to torque in three passes. Preload becomes higher and more consistent, and the block threads are protected. ARP makes these fasteners in 8740, a chrome-moly steel brought by heat treatment to 200,000 psi tensile strength. As a reference point, an engine's original fasteners generally fall into classes 10.9 and 12.9, whose minimum ranges from 150,800 to 176,900 psi. These 8740 studs in M10 take up to 1,000 hp on this four-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

The studs are screwed into the block by hand, with no torque. For a permanent assembly, ARP's instructions permit a Loctite thread locker, provided full tightening is done before the product cures.

Follow the cap tightening sequence recommended by the manufacturer when bringing the nuts up to torque; the kit's instruction sheet details each step.

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 the bores line-honed if necessary with the final fasteners and lubricant.

Torque figures taken from the ARP 203-5404 instruction sheet, in the revision in force on the day of publication. In the event of any difference, the manufacturer's instruction sheet prevails. Read the ARP 203-5404 instruction sheet

Technical guide

The torque figures given only apply with ARP assembly grease, never with engine oil.

The ARP brand

Founded in the early 1970s by Gary Holzapfel, who came from the aerospace industry, ARP (Automotive Racing Products) set out to prevent fastener-related engine failures in motorsport. Its thousands of part numbers are designed and manufactured in California, in materials chosen for each use.

Advantages over the original bolts

Criterion	Original main bolts	Reinforced ARP studs
Tightening	Bolt screwed straight into the block	Three torque passes, steady build-up
Threads in the block	Loaded by the turning bolt at every tightening	Stud screwed in by hand, no torque
Refitting the caps	Cap held by hand while the bolts go in	Cap guided by the two studs

When studs become necessary

• Turbocharged or supercharged engine, or boost raised beyond stock
• Build that increases engine speed or stroke
• Bottom end overhaul
• Caps that have moved or marked block threads
• Track or rally use with repeated loads

Vehicle compatibility

Why is it the most cost-effective solution?

On a tuned 3S, ARP 8740 studs clamp the main caps harder than the original bolts and so limit the risk of bottom-end damage. Their cost is small next to repairing a crankshaft and a block.

Consider the crankshaft main bearings

When the bottom end is open, the bearings are replaced too. Here are the tri-metal crankshaft main bearings designed for these engines: