Todays market is full of different types of piston ring compressors. A quick search of the usual selling sites will come up with a huge variety of different tools for the job. Which one you choose will depend on a few factors. So lets have a look at the 3 main types available.

The Taper

Available from a variety of different manufacturers, the taper type piston ring compressor works extremely well. Leading brands such as ARP and Wiseco make these in various different sizes to suit both imperial and metric bores.

It works by the tube having a hole of the same size as the bore at the bottom, which gets larger at the top. You can simply align your ring gaps, apply lube, then place your piston assembly into the tool, and press it into the bore.

Advantages. As the tool is solid, you can use one hand to keep it flush to the block/liner whilst the other moves the piston. These make fitting easy, with little chance of ring damage due to one “popping out” between the tool and the block face. Keep ideal piston ring alignment.

Disadvantages. Individual prices are high. The tool is one size only. This means that unless you work on a particular bore size/engine often, then you will need a whole batch of these, and they aren’t the cheapest. There are adjustable ones available, but these work within a very limited bore range.

The Ratchet Roll

Probably the most common type ring compressor. This budget piston ring compressor used by home mechanics and people in the trade. Its sold by many auto spares shops, and usually stocked locally.

It works by turning the handle once the piston is inside. This tightens the “roll” and a ratchet holds it from expanding again.

Advantages. Works with pretty much any size (within reason). Cheap.

Disadvantages. As you tighten the roll, the overlap can cause piston rings to rotate from their desired position. As the roll can flex, it can be very difficult to hold it flush to the block, so commonly allow rings (usually the oil scraper/oil control ring) to pop out between the tool and block/liner surface, and if you’re not careful, damage can happen.

The Pliers

A very adaptive kit that comes with a range of attachments allowing it to suit most bore sizes in just one kit.

Select the correct attachment and compress it over the piston rings, ratchet keeps compressed. Put the skirt of the piston in the bore then tap the piston down.

Advantages. Keep reasonable piston ring alignment. Reasonably priced. Adapt to large range of sizes.

Disadvantages. Not the easiest to keep flush to the block, but much better than the roll type.

The Wrinkle Band

These are adjustable, and suit a wide range of bore sizes.

The wrinkle overlap position is adjusted, then there is a small screw for finer adjustment, before tightening over the piston rings.

Advantages. Suit a wide range of bore sizes. Relatively cheap

Disadvantages.  Fiddly to use and adjust. Not 100% reliable at allowing rings to pass directly between inside the tool and into the bore.

Our Recommendations

Depending on how often you would need to use the tool would make the majority of the decision for you. If as a hobbyist you have only one piston to fit, the best option would likely be the Ratchet Roll type from a budget point of view. Most engine builders use the Pliers type, as they have been around for many years and reasonably priced. The builders we spoke to said they prefer to use the Taper type, and now they are becoming more common on the market, their price is dropping to a more affordable rate.

Engine building Tips and guides. Commonly used specialist tools in engine, gearbox and motorsport industry. Guides on how to rebuild, torque settings, clearances, bores, weights, bearings, engine specifics. Wiring guides.
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