Reinforced ARP main studs for Ford Zetec-E 2.0

The Ford engine concerned

This kit is for the 2.0-litre Ford Zetec-E four-cylinder, 16 valves, in the Blacktop version introduced in 1998, fitted notably to the first-generation Focus and the Cougar.

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.

These ARP 8740 steel studs, 7/16 inch, replace the original main cap fasteners of the Zetec-E. The block threads are cleaned, then the studs are screwed in by hand. With the caps in place, washers and threads are lubricated with the ARP Ultra-Torque supplied, and the nuts are tightened in three equal passes, in the manufacturer's sequence: 36, 72 then 108 Nm. ARP advises against engine oil, as it raises friction and makes the tightening less consistent.

Material: 8740, a chrome-moly steel that ARP specifies at 200,000 psi tensile strength, with threads rolled after heat treatment. Factory-fitted fasteners usually belong to classes 10.9 and 12.9, with 150,800 to 176,900 psi minimum tensile strength. The 8740 studs in 7/16 inch hold up to 1,200 hp on this four-cylinder engine (calculated estimate).

Technical specifications

Tightening torque

Fitting the studs: screwed into the block by hand, without a tightening tool. Where a permanent installation is wanted, ARP accepts a thread locker of the blue Loctite type on the block-side thread, provided the nuts are tightened before it sets; none goes on the nuts or with ARP grease.

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.

Moving to reinforced fasteners changes the clamping force on the caps. After installation, the size and roundness of the bores are checked, then align honed if needed, always with the final fasteners and lubricant.

Values taken from the ARP 151-5404 instruction sheet in force at the date of publication; the official instruction sheet prevails should any difference appear. Read the ARP 151-5404 instruction sheet

Technical guide

Tightening is done with ARP assembly grease: the torque figures in the table were established with it, not 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	ARP studs
Tightening	Bolt screwed into the block, turning under torque	Nut alone turns, tightened in three passes
Block thread	Takes the rotation of the bolt at each assembly	Stud placed by hand, no effort
Positioning the caps	Cap to be held while screwing	Cap guided by the studs

When studs become necessary

• Zetec-E 2.0 tuned with a turbo, supercharger or raised rev limit
• Power well above the original 130 hp
• Bottom end removed for a rebuild
• Main caps that move or tired block threads
• Repeated sporting use, track, rally or drag

Vehicle compatibility

Why is it the most cost-effective solution?

A Zetec-E taken beyond its original state, with a turbo or supercharger or simply high revs, subjects the main caps to loads that the standard fasteners tolerate poorly. These ARP studs make the clamping more reliable for an outlay far lower than that of a bottom end to rebuild.