Powerbuilt Piston Ring Compressor Set 940387 — 2-7/8in to 4-3/8in Bands with Ratcheting Pliers & Case

The Powerbuilt Piston Ring Compressor Set with ratcheting pliers (model 940387) compresses piston rings quickly and evenly for safe, damage-free piston installation across 2-7/8" to 4-3/8" diameters.

When you’re replacing pistons or rebuilding an engine, compressing rings evenly is essential to avoid scoring bores or bending rings. This complete kit combines six interchangeable steel bands sized to cover a wide range of piston diameters with a ratcheting clamping tool that delivers controlled, incremental compression. Everything snaps into a heavy-duty carry case with laminated, permanently attached instructions so you can follow the right steps on the bench or in the bay.

How does this compressor set adapt to different piston sizes?

The kit includes six band sizes that overlap to cover pistons from 2-7/8" (73 mm) up to 4-3/8" (111 mm). Each band slides over the piston and is tightened to the exact circumference you need, so one set fits many engines without stretching or modifying the rings.

• Six adjustable steel bands for precise diameter fits.
• Covers incremental ranges: 2-7/8" to 3-1/8", 3-1/8" to 3-3/8" and up to 4-3/8".
• Overlapping sizes reduce the need for additional compressors.

Why use the ratcheting pliers instead of a standard clamp?

The included ratcheting lock pliers let you tighten the band gradually and hold pressure securely while you install the piston. Ratcheting action prevents sudden releases and allows one-handed control, helping maintain ring alignment during insertion into the cylinder.

• Ratcheting mechanism for consistent, repeatable compression.
• Locking action holds the band firmly without slipping.
• Improves safety and reduces the chance of ring distortion.

What protection and reference materials are provided with the kit?

The compressor set is stored in a robust carrying case that protects parts and keeps everything organized. Inside the lid you’ll find laminated, professionally written instructions with photos that remain readable even in a shop environment, so you can confirm proper technique anytime.

• Durable molded carry case for transport and storage.
• Laminated instruction sheet with step-by-step photos attached to the case.
• Instructions developed by a repair manual writer for clear guidance.

How will this tool help during piston installation on the job?

By holding rings uniformly compressed, the tool minimizes the risk of ring snagging or misalignment, making piston drop-in smoother and faster. The controlled compression also reduces potential damage to ring ends and the cylinder walls, letting you spend less time correcting installation errors.

• Speeds up piston installation with reliable ring control.
• Reduces rework from nicked rings or scored cylinders.
• Useful for single-engine repairs and professional shop work.

Who is this for: The Powerbuilt 940387 piston ring compressor set is designed for home mechanics, mobile technicians, and professional engine shops who need a versatile, durable tool for piston installation across common small- and mid-size engine bores. It’s ideal for anyone rebuilding engines, replacing pistons, or performing cylinder work who wants a compact kit with clear instructions and dependable clamping performance.