Reinforced ARP main studs for TOYOTA 7M

The Toyota engine concerned

This kit is for the 7M-GTE, Toyota's 3.0-litre, 24-valve turbocharged in-line six (2,954 cc). It powers the third-generation Supra Turbo (A70, MA70).

From the factory, the 7M-GTE's main caps are tightened by Toyota bolts; the 12 mm studs in this kit replace them.

Reinforced ARP studs for main bearings

On a crankshaft, the main caps are what hold the shaft against the loads passed on by the connecting rods. If their clamping force drops, the cap shifts slightly on its parting line at every cycle: the mating faces brinell, then the bearing bore goes out of round.

These ARP 8740 steel studs, 12 mm, replace the original main cap bolts of the 7M-GTE. Once the block threads have been checked, they are screwed in by hand only, then the caps, washers and nuts are fitted. Threads, nuts and washers get ARP Ultra-Torque, which the instructions prefer to engine oil. The final tightening of 122 Nm (90 ft-lb) is reached in three equal passes, in the order set by the manufacturer: 40, 81 then 122 Nm. 8740 is a chrome-moly steel heat treated by ARP to 200,000 psi tensile strength, with threads rolled after heat treatment. To put this figure in context, standard engine fasteners mostly belong to property classes 10.9 and 12.9, i.e. 150,800 to 176,900 psi minimum tensile strength. These 8740 studs in 12 mm take up to 1,800 hp on this six-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

No torque is applied to the stud as it goes into the block: it is screwed in by hand. For a permanent installation, the ARP instruction sheet allows a Loctite thread locker, provided the tightening is completed before the product cures.

The nuts are tightened in the sequence the manufacturer specifies for the main caps; the instruction sheet supplied with the kit describes the full procedure.

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 align honed if necessary with the final fasteners and lubricant.

Values taken from the ARP 203-5402 instruction sheet in force at the date of publication; the official instruction sheet prevails should any difference appear. Read the ARP 203-5402 instruction sheet

Technical guide

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

The ARP brand

ARP, short for Automotive Racing Products, was born in the early 1970s on the initiative of Gary Holzapfel, an engineer from the aerospace sector, in response to the engine failures caused in racing by inadequate fasteners. Today the brand produces thousands of part numbers in California, offered in several materials depending on the application.

Advantages over the original bolts

Criterion	Original main bolts	Reinforced ARP studs
Fitting	The bolt screws straight into the block	The stud is placed by hand, the nut comes after
Block threads	Driven round by the bolt at every tightening	Not stressed by tightening the nuts
Cap position	Cap held by hand while screwing	Cap guided and centred by the studs

When studs become necessary

• Supra Turbo A70 built for track, drag or road
• Power well above the original
• Engine stripped for a complete refresh
• Main caps working loose or worn block threads
• Forged pistons, rods or crankshaft going in

Vehicle compatibility

Why is it the most cost-effective solution?

A 7M-GTE built well beyond its original output, for track, drag or road, puts loads on the main caps that the standard fasteners were never designed to carry. Securing the caps more firmly protects the crankshaft and the block, at a cost far below that of replacing a block or a crankshaft.