Reinforced ARP crankcase through-bolts for PORSCHE 964

The Porsche 964

ARP lists this part number for the Porsche 964. The ARP page for kit 204-5410 gives no displacement, year or contents, so the compatibility table reproduces the ARP application of the kit as published, with no engine code or year inferred.

The factory part number of the original crankcase fasteners replaced by kit 204-5410 is not published in our sources and so does not appear on this page. The ARP catalogue lists kit 204-5410 among its crankcase kits.

Reinforced ARP crankcase through-bolts

On a Porsche 964, the bottom end is a crankcase in two halves joined around the crankshaft by the crankcase fasteners. These fasteners hold the halves together against the connecting-rod loads; if they relax, the crankshaft works in housings that lose their shape.

This kit brings together the ARP crankcase hardware for the Porsche 964, in 8740 steel. 8740 is a chrome-moly steel heat treated by ARP to 190,000 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. The kit replaces the original crankcase 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

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.

When to upgrade the crankcase fasteners

• Porsche 964 being built to make much more power than standard
• Engine stripped down to fit a forged crankshaft, rods or pistons
• Crankcase threads and seats to be checked before fitting stronger fasteners
• Intensive track, rally or hill-climb use
• Complete bottom-end rebuild with replacement of the crankcase fasteners

Vehicle compatibility

Why is it the most cost-effective solution?

On a modified Porsche 964, the crankcase takes the crankshaft loads through its fasteners: reinforcing them protects the crankcase seats and the crankshaft.