Reinforced ARP crankcase studs for PORSCHE 911-930 Turbo

The Porsche 911-930 Turbo

ARP lists this part number for the Porsche 911-930 Turbo. The ARP database names it "CASE HALVES STUD KIT" and gives no displacement, year or contents: the table reproduces the application as published, with no engine code or year inferred.

The factory part number of the original crankcase-half fasteners replaced by kit 504-9501 is not published in our sources and does not appear on this page.

Reinforced ARP crankcase studs

On a Porsche 911-930 Turbo, the bottom end is made of two crankcase halves assembled around the crankshaft. The crankcase studs keep these halves pressed together despite the loads passed on by the connecting rods; if they relax, the crankshaft housings can lose their shape.

This kit brings together the ARP crankcase-half studs for the Porsche 911-930 Turbo, in stainless steel. The kit is made of stainless steel, according to the ARP product export; the grade is not specified in our sources. The kit replaces the original crankcase-half fasteners; no strength value is published for this part number.

Technical specifications

Tightening torque

The torque and tightening sequence are to be read in the instruction sheet supplied with the kit.

Technical guide

Before fitting, check the condition of the crankcase threads and seats.

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 fasteners	Reinforced ARP studs
Material	Depends on the original crankcase fastener	Stainless steel, kit 504-9501
Manufacturer	Factory or replacement part	ARP, USA
Origin	Varies with the original part	USA (ARP database)

When to upgrade the crankcase fasteners

• Porsche 911-930 Turbo whose engine makes far more power than the original
• Engine overhaul with a forged crankshaft, rods or pistons to install
• Crankcase being reworked: threads and parting surfaces to check before reassembly
• Track, rally or hill-climb use
• Complete reassembly of the crankcase halves with replacement hardware

Vehicle compatibility

Why is it the most cost-effective solution?

On a modified 911-930 Turbo, the crankcase halves must stay tightly joined under the crankshaft loads: reinforced crankcase hardware limits the risk of the parting surfaces working.