Reinforced ARP main studs for FORD Escort 1600

The Escort 1600 engine

This kit is intended for the Ford Escort 1600, whose engine is a 1.6-litre four-cylinder. ARP lists it as a two-bolt main stud kit for this application, without giving an engine code or production years.

Originally, Ford fasteners hold the crankshaft main caps; the 12 mm studs in the kit take their place.

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 become indented, then the bearing bore goes out of round.

The ARP 8740 steel studs, 12 mm, in this kit replace the original main cap fasteners on the Escort 1600. The block threads are cleaned and checked first, then the studs are screwed in by hand only. Caps, washers and nuts follow; studs, nuts and washers are coated with ARP Ultra-Torque, as the instructions advise against engine oil. The nuts are tightened in three equal passes, in the order set by the manufacturer, up to 122 Nm (90 ft-lb): 40, 81 then 122 Nm. 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. On this four-cylinder engine, the 8740 studs in 12 mm are rated for 1,200 hp at most (calculated estimate).

Technical specifications

Tightening torque

Fitting the studs: screwed into the block by hand, without a tightening tool. For a permanent installation, the ARP instruction sheet allows a Loctite thread locker, provided the tightening is completed 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.

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

The torque figures above come from the ARP 151-5403 instruction sheet, revision applicable at publication. The official instruction sheet is authoritative in the event of any difference. Read the ARP 151-5403 instruction sheet

Technical guide

All the torque values on this page assume ARP assembly grease; with engine oil they are no longer correct.

The ARP brand

Coming from the aerospace industry, Gary Holzapfel founded ARP (Automotive Racing Products) in the early 1970s to put an end to engine failures caused by weak fasteners in motorsport. The company designs and manufactures thousands of part numbers in California, in several material grades depending on the application.

Advantages over the original bolts

Criterion	Original main bolts	Reinforced ARP studs
Tightening	The bolt's rotation loads the block thread	Only the nut turns, the block thread is left unloaded
Repeated refits	The block thread wears with every screwing	The stud stays in place, the block thread is preserved
Locating the caps	The cap has to be held while screwing	The studs guide and hold the cap

When studs become necessary

• Escort 1600 built for the track, rally or drag racing
• Revs or power well above the original
• Block opened to rebuild the whole bottom end
• Main caps that shift or marked block threads
• Fitting a new forged crankshaft, rods or pistons

Vehicle compatibility

Why is it the most cost-effective solution?

An Escort 1600 built for the track, rally or drag racing asks more of its main caps than the original design allowed for. By clamping them more securely, these studs protect the crankshaft and the block at a cost far below replacing a block or a crankshaft.