Besides snap rings that are difficult to remove or install without a proper tool, piston rings can be another source of trouble when rebuilding a car engine. Without the right tool, you can easily deform these important metal rings and make them less effective. And if you are unlucky, the piston rings can break and become totally unusable.
What Are Piston Rings?
If you don’t know what are piston rings or you are just getting started with rebuilding engines, they are thin tempered steel rings that go around the piston head of an internal combustion engine.
Piston rings seal the gap between the piston and the cylinder wall or bore to maintain engine compression. It is for this reason that they are also called compression rings.
They prevent the air/fuel mixture from escaping the combustion chamber and blowing by the piston into the crankcase, which often results in a loss of horsepower.
Piston rings also prevent excessive oil from entering the combustion chamber. They scrape off excess oil from the cylinder wall. So, whenever you hear that a car is burning oil it is often due to failing compression rings.
Another function of piston rings is to create a contact point between the piston and the engine cylinder that helps to dissipate heat from the piston.
So in a nutshell, bad piston rings will cause blow-by, loss of compression, and burning of oil in a combustion engine.
You are probably wondering, how many compression rings does a piston have? And based on the few 2-stroke and 4-stroke engines I have rebuilt as a hobbyist mechanic, most pistons have 2 or 3 compression rings. But I understand there are engines that have up to 4 piston rings.
How to remove and install piston rings
As I mentioned, you can put piston rings on or off with a tool or by hand. The problem with not using a tool or using the wrong one is that you increase the risk of deforming the ring or breaking it.
The best way to install or remove piston rings is with piston ring pliers. These are special types of automotive pliers with a unique jaw shape that allows for easy manipulation of piston compression rings. Some advanced piston ring pliers grasp a ring in multiple places to prevent them from deforming.
The main advantage of using piston ring pliers to put piston rings on is that they ensure proper installation and reduce the risk of damage to the ring. However, you must use the tool properly.
How to use piston ring pliers
The removal and installation of piston rings using ring compression pliers is quite easy and straightforward. Just follow these simple steps:
Note: The assumptions in these steps is that you have already dismantled the engine and taken out the piston assembly.
Step 1: Identify the compression rings on the piston.
A piston has two types of rings: compression rings and oil rings. Compression rings are brittle steel rings that sit in the first and second grooves on the piston from the top. In pistons with three compression rings, the lowest ring will be in the third groove.
On the other hand, oil ring components are thinner and more flexible and occupy the bottom-most groove on the piston. They comprise the wave-shaped space expander and two side rails. You don’t need a tool to install or remove the oil ring stack.
2 Locate the end gap on the piston ring.
Find the opening for the compression ring in the top-most ring groove. You can either turn the piston around or rotate the compression ring so that the end gap faces you.
3. Hook the piston ring pliers onto the ring.
Place the jaws of the piston ring pliers in the end gap and hook each end of the piston ring to the pocket on each plier jaw.
4. Expand the compression ring
Squeeze the handles of the pliers together to widen the ring end gap. Expand the ring so that its diameter is wider than that of the piston.
As you expand the end gap, hold the other side of the ring with your hand to prevent the ring from snapping and flying around. Be cautious not to open the ring too much because you can break it. Also, apply gentle pressure while squeezing the pliers.
5. Remove the piston ring
Gently draw the ring from the piston groove, off the top of the piston, and place it aside. Repeat the steps for the next piston ring(s).
Follow the same steps to install the piston rings but start from the lower groove. While installing piston rings, make sure the markings on them face upwards. Also, follow the repair manual to position the ring end gaps correctly on the piston for maximum engine performance.
Which Are The Best Piston Ring pliers?
There are several types and brands of piston ring pliers but these are some best in the market.
Lisle 33500 Piston Ring Installer – Best Budget Tool
The Lisle 33500 piston ring pliers are a household name for mechanics who repair small engines. They are simple, affordable, and easy to use to expand the piston rings of small engines for installation or removal.
You don’t need a lot of pressure to open small piston rings and these pliers provide just enough leverage. However, this does not mean that you can only use Lisle 33500 to repair engines of motorcycles, Go Karts, ATVs, lawnmowers, and other 2-stroke engines, no! You can use them to rebuild automotive engines especially if you are a home mechanic doing just one motor or two. But you need to be extra careful not to damage large piston rings as you expand them.
One of the downsides of this style of ring pliers is that they only grip the very end of the ring gap, which can cause the ring to twist out of shape. It is also easy to over-expand and break automotive engine rings with these pliers because you need a little bit more pressure to spread them apart.
Lastly, these Lisle ring pliers do not have the strongest jaws for expanding the tough car engine piston rings.
Hazet 790-3 Piston Ring Pliers – Best Quality
Whether you are rebuilding the engine of your Harley-Davidson bike or Dodge Ram muscle truck, these German-made piston ring pliers will get you through the piston ring work.
The Hazet 790 pliers have a similar construction as the Lisle but feel sturdier. They are nickel plated and the jaws have a slot that prevents compression rings from twisting when expanded.
But you still need to support the circumference of the piston ring with your other hand to protect it because messing with the piston rings is the last thing you want when repairing an engine. It could make you rebuild the motor again and that’s costly.
A similarly built set of piston ring expander pliers to Hazet 790 is the NWS 205-15 set. It is also made in Germany with high-grade alloy steel. If you like NWS line of pliers, this might be a good set to add to your collection of pliers for automotive repairs.
New Stens Piston Ring Expander Pliers 751-909 – Best Overall
Not all piston ring pliers take the form of traditional pliers. Some are more advanced with a compound action mechanism and multiple gripping points for the ring.
One such set of pliers is the New Sten Piston ring pliers set. It is the best in its category and even superior to the traditional type because it grasps a piston ring in multiple places to support it. This makes taking the ring on and off the piston very easy.
The only letdown of the New Sten ring expander pliers is the handles because they don’t have rubber grips. Even though they are contoured, the handles feel a bit uncomfortable in the hands. But I have found that wrapping some masking tape or foam around the handles improves the grip significantly. You can also plastic dip them if you like.
That said, these American-made compound action ring pliers by Stens are perfect for professional mechanics who rebuild engines for a living. It works for most common ring sizes, typically between 2″ and 4″.
Generally, irrespective of which type of piston ring pliers you choose, just know that ring pliers are better than nothing when rebuilding an engine. They will not only help speed up the process of assembling engine pistons but also reduce the risk of breaking compression rings.
If you have tried to replace piston rings without a tool, you know it is very easy to deform or break the rings. But one thing is for sure, a set of piston ring pliers makes work easier. It is one of those tools that make you ask yourself, “Why didn’t I buy it years ago?” Piston ring installer pliers are an essential tool for engine rebuild.