ARP 901-8625 86.25mm Bore Tapered Piston Ring Compressor Billet Aluminum Tool

Vehicle Fitment

• Universal - fits any engine with an 86.25mm (approximately 3.396") cylinder bore diameter, including metric-bore applications in Japanese, European, and domestic performance engines

Fitment Notes

• Universal tool - not vehicle-specific; confirm your engine's exact bore diameter before selecting this size
• Relieved on the bottom to accommodate wire O-ring pistons; confirm O-ring clearance with your specific piston design
• For bore sizes outside 86.25mm, ARP offers this same tool in increments of 0.25mm across a full metric and SAE range

Features

• CNC-machined from 6061-T6 billet aluminum tube for precise bore diameter accuracy and long service life
• True-radius tapered inner surface guides piston and rings into the bore smoothly and without distortion
• Type 3 hard anodized finish for superior durability and resistance to wear, oil, and solvents
• Relieved on the bottom to accommodate wire O-ring pistons during installation
• Bore size (86.25mm) prominently engraved in 3/4" high numbers for fast identification in the shop
• True-radius design is far superior to conventional ratchet-style or band-type ring compressors
• Widely used and acclaimed by professional engine builders for accuracy and ease of use

Specifications

• Bore Size: 86.25mm (approximately 3.396")
• Material: 6061-T6 billet aluminum
• Finish: Type 3 black anodized
• Dimensions (L x W x H): 9.8 x 5.8 x 2.3 in
• Weight: 1.54 lbs
• Adjustable: No - fixed bore size
• Fitment Type: Universal

Included Components

• 1x ARP Tapered Piston Ring Compressor (86.25mm bore)

Product Description

The ARP 901-8625 is a precision tapered piston ring compressor machined for 86.25mm bore engines. Unlike traditional adjustable band-type compressors that can distort rings or cause uneven compression, the ARP design uses a true-radius tapered inner surface that matches the exact bore diameter. This guides the piston and rings smoothly and evenly into the cylinder without snagging, twisting, or pre-loading the rings unevenly - resulting in faster, cleaner, and more reliable engine assembly.

CNC-machined from 6061-T6 billet aluminum and finished with Type 3 hard anodizing, the 901-8625 is built to withstand repeated use in a professional shop environment. It is relieved on the bottom to accommodate wire O-ring pistons, and the bore size is engraved clearly on the body for quick identification. This tool is an essential for any engine build using 86.25mm bore pistons, whether for a daily driver rebuild or a high-output performance application.