So, you have a set of pistons that you want to re-ring, but you don't which rings to order. Here, we go over the options you have for measuring your old rings or ring grooves so JE can get you the rings you need.
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Forged pistons are a durable, high-performance option for many engines, and last a long time in various applications. Because of the lasting quality of forged material, replacing the piston(s) is not always necessary. JE pistons has many customers that have been running the same pistons for a long time, and they're still well within safe running condition. However, these customers still need to periodically replace rings as practice of proper maintenance to help maintain efficient sealing and keep blow-by to a minimum.
In many cases, forged pistons will last a long time and be remain safe to re-use, but replacing the piston rings periodically is important to retain performance.
Replacing piston rings is easy, but ordering the correct replacement rings is not always cut and dry. If you have a JE piston'or set of pistons'you need rings for, you can usually provide the part number or job number over the to a JE tech expert and they'll be able to tell you what ring pack part number will get you going again. That's the easy situation.
However, there are many racers, builders, and enthusiasts out there that have some JE pistons that don't have any laser marked numbers on the bottom of the pin tower. When there is no number present, this means the piston was manufactured before laser marking was implemented in .
If your JE pistons have a job or part number, simply call JE, provide that number, and they'll get rings coming to you! If they don't have any numbers, you'll need to follow the steps below to narrow down which ring pack you'll need.
Need help identifying other markings on your pistons? Check out our guides for Powersports and Automotive.
Analyze Your Used Rings to Identify New Ones Needed
So, how do you know what rings to order if you don't have a reference number? Here's some tips to help you be prepared with the data you need to order the correct replacement rings.
First, make sure your old/worn out rings are off the piston. With the rings off, measure the axial height (this is the thickness of the ring) and radial width (the width of the ring from the outer edge to the inner edge) of the oil ring assembly with a set of calibrated calipers or a micrometer, whichever you have easy access to. Make the sure the oil ring assembly is assembled correctly'like it would be when sitting in the ring groove'while measuring. It should be assembled with two oil rings sandwiching the expander ring. Measure and record the axial height of the assembly, as well as the radial width.
Measure and record both the axial height and radial width of the oil ring assembly while off the piston. Using either a set of calipers or a micrometer is sufficient.
After recording those measurements, perform the same axial height and radial width measurements of your compression ring(s). In addition to these measurements, you'll want to look for specific compression ring characteristics, such as shape, bevels, notches, and markings, that can determine which type of ring(s) your piston originally came with. Note that ring characteristics will vary between top and second compression rings. Compare your compression ring characteristics to the JE chart below.
Analyze and compare your rings to these charts to help identify which specific style rings your piston(s) came with.
Want to know more about ring material and design? Read this!
After all your measurements are recorded and you have identified what style compression rings you have, you're ready to call in and provide your information to a JE tech expert so they can get the correct part number coming to you.
Don't forget to record measurements for your compression rings, too!
Don't Have Old Rings? Measure Your Ring Grooves
In some cases, you may acquire a set of used pistons that are still in good condition, but did not come with the old rings. If these used pistons do not have a job number or part number laser-marked, you'll need to take a few measurements of the ring grooves to accurately track down which exact ring set you'll need for your pistons.
First, measure the axial height of each ring groove. Axial height refers simply to the height of the ring groove itself. For exact measurements and engineering purposes, JE uses precision-sized pin gauges to measure ring grooves.
JE uses pin gauges for more exact measurements.
However, not every person will have a set of pin gauges in their garage. In this case, use a set of calipers to take as accurate a measurement as possible. This will get you close enough for the JE tech experts to know which ring pack your piston was designed for. Take the axial height measurement for each compression groove and the oil ring groove.
Most people don't have pin gauges, so using a set of calipers to get an approximation of ring groove axial height is okay. To measure the smaller, compression ring grooves, use a set of feeler gauges in conjunction with your calipers.
It's important to note that some pistons are designed and machined with accumulator grooves. While they can be confused as a ring groove, they are not designed to house any rings. When present, accumulator grooves are set between the top and second compression ring, and are purposed to allow any gases that make it past the top ring to expand, preventing ring flutter and reinforcing ring seal.
If you see a V-shaped groove between the top and second compression ring grooves, note that this is an accumulator groove, and is not intended to house any rings.In addition to measuring axial height of the ring grooves, the radial depth will also need to be measured. Radial depth is the distance from the outermost surface of the ring groove to the inner wall of the ring groove. Radial depth may be difficult to measure to measure without pin gauges, but if a close measurement is taken and provided in conjunction with the axial height and bore size, JE tech experts should be able to narrow down the ring pack needed.
Bore size is another critical measurement to be taken and provided to help identify the correct rings.
JE would typically use a blade mic for quick and accurate groove radial depth measurements, but if you can get to a close measurement with the tools you have, JE tech experts can work on narrowing it down for you based on other measurements.Whether you're providing measurements of old rings or ring grooves, providing all critical measurements'axial height, radial depth, and bore size'is important to help JE figure out what rings you need. This is because there are some situations where two ring packs may have the same axial height, but varying radial depths.
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Don't Have the Means to Measure? Let JE Take Care of It
If you're unsure about taking accurate enough measurements, or you don't have the proper means to provide the measurements yourself, JE would be happy to take care of it for you. Simply contact JE and let them you know you need measurements taken for new rings, send in your piston(s), and JE will take exact measurements and let you know which ring set to purchase.
If you'd rather have JE perform the measurements to be sure you're getting the correct ring pack, just give them a call to coordinate sending your piston(s) in!Ring gap is absolutely critical to engine performance and longevity''and, one of our number-one tech questions. Today we explain why rings need a gap, how to do it, and some common ring-gapping mistakes.
If you're a frequent reader of our articles here, you may have noticed that our 'tech' stories tend to fall into a few major categories. Some are to let you know about new stuff that's just hitting the market. Others are intended to give you an in-depth look at the engineering and technology behind the aftermarket products you're selecting for your engine builds. And the rest are simply a way to answer the question: 'how do I do that?'
Today, we're looking at setting ring gap ' a topic that might not exactly elevate your heart rate, but something that is absolutely critical to engine performance and longevity'and, one of our number-one tech questions. Our expert guiding us today is Wiseco's Nickolaus DiBlasi.
Because piston rings need to be expanded to fit over the diameter of the piston itself before they find their home in the ring grooves, they have to be split in some way in order to allow installation. At the same time, the gap between the ends of the ring needs to be kept as small as practical, for a number of reasons.
'Let's first look at the job of the top compression ring,' DiBlasi explains. 'The main objectives for the top ring are to hold in compression and pass heat from the piston to the cylinder. From that point, energy is taken away from the cylinder using water in the water jackets. Due to this fact, the top ring sees the most amount of heat.' With that in mind, it's clear that the smaller the gap, the less opportunity there is for combustion chamber pressure to make its way past the first ring, and the more contact the ring has with the cylinder wall in order to transfer heat.
A perfectly gapped ring will have ring ends completely parallel to eachother when installed.In a perfect world, piston rings that perfectly fit the bore with the ends butted together would be ideal. But as anyone who has tried to make an omelet and ended up with a 'breakfast scramble' can tell you, the world is an imperfect place. As the block, piston, and rings all heat up, they change dimensions ever so slightly, and at different rates. DiBlasi takes it down to the molecular level:
'With any material, heating it induces more energy into parts. As the atoms and molecules in the parts are heated, they start to move around more and the gap between them increases. The added space between atoms and molecules is the expansion that you noticed in pistons, rings, and everything else in the world. Each material is comprised of different elemental mixes, so the bond structure and spacing of atoms and molecules are different. This is the reason why you see some materials expanding at significantly different rates than each other. Case in point is aluminum pistons in an iron block. The aluminum expands significantly more.'
We accept tradeoffs in expansion rates in order to get the best compromise in material properties for each component, but that means we need to take it into account when we put all these different parts together and ask them to play nice with each other. Per DiBlasi, 'Since the top ring will see a majority of the heat, they expand quite a bit. The gap that you create in the top ring is to accommodate the maximum expansion that you anticipate the top ring requiring. This is very critical to understand, as the top ring is responsible for holding in compression. There is a fine line of making sure that top ring is not bypassing compression, but not expanding so much that the ends run into each other.'
'If the top ring is gapped too small, when it expands the ends will run into each other,' DiBlasi continues. 'As the engine heat-cycles back and forth through its maximal temperature, the top ring expands and contracts. If the gaps are too small, the top ring ends will run into itself. Since the ring has nowhere to expand at this point, the outward force applied to the cylinder increases. This added force introduces even more heat and the ring expands further. Once that happens, catastrophic failure will occur rapidly as it is a continuous cycle of more heat, more outward pressure, and nowhere for the ring to expand into.'
If that sounds bad, it is.
'The increased force to the cylinders starts to hold the piston tighter to the cylinder wall,' DiBlasi explains. 'This added resistance, in conjunction with heat starts to soften the piston. It first will start to pull on the ring grooves and lands, spacing them further and further apart. Next, the lands grow excessively in diameter due to the heat they are seeing, as the rings can no longer adequately pull enough heat away from the piston into the water jackets. At this point, the top land, perpendicular to the pin axis, will be flattened out as it grows with excessive heat. In extreme cases, the top of the piston is ripped completely off the part.'
Clearly, that's not something you want happening. Per DiBlasi, 'Many piston failures occur due to this reason, and more often than not when we are diagnosing the problem we see that the rings were either not gapped enough, or not gapped at all.'
Before you remove any material from the ring end, it's important to check your starting clearance. The ring must be perfectly square in the bore to get an accurate measurement.The best way to prevent this kind of runaway destruction is, surprisingly enough, to pay attention to the information provided with your new Wiseco pistons and rings. 'We have outlined our recommendations that are included with pistons. These are also available in our catalogs and website,' DiBlasi adds.
The process begins with inserting the ring into the bore, and making sure it is square using a squaring tool to align it properly. A feeler gauge inserted into the ring gap will show you the existing dimension, and from there you can make your adjustments. For a street engine, multiplying your bore size by 0.004in will give you the top ring gap you are looking for.
For high performance engines, the multiplier changes to add more clearance, but the math stays the same:
For the second ring, the process is the same, but with a slightly different gap, based on application:
The reason for these variable specifications is that different types of engines put radically different heat and pressure loads on the ring package. DiBlasi explains, saying, 'Let's look at an LS3 engines that many of our customers have, including myself. If you are building a fun street naturally aspirated LS3 you can expect about 525 horsepower out from it. The heat the rings will see will be very similar to what they are in factory form. Let's take another person with an LS3 that drops in a new Eaton positive displacement blower. They can make about 1,100 horsepower out of the same bore, stroke, and general engine combination as the N/A guy. With over double the power output it will significantly increase the cylinder pressure and heat that rings will see. The ring end gaps will need to be substantially larger than the engine with 525 horsepower.'
Setting ring gap can be a slow process, but by paying attention to how many turns on a manual filer it takes to remove a certain amount of material, you can get a feel for what each ring will need and get closer to the finished spec in fewer steps. Remember to only file one end of the ring, and take care to avoid damaging any coating the ring may have.What it all comes down to is the same thing we mentioned at the start ' heat. The more heat, the more expansion in the ring material, and the more clearance that is required. 'Forced induction engines are adding significantly more cylinder pressure than a naturally aspirated engine. The added air and fuel in forced induction engines acts as additional displacement in the same space as the naturally aspirated variant,' says DiBlasi. 'That added cylinder pressure is added heat. Since heat is the driving force behind end gaps, the hotter cylinders require more end gaps. Similarly, two naturally aspirated engines with different compression ratios will, too. If one engine is 9:1 and the other is 14:1, the higher compression version will need the larger of the two gaps.'
Wiseco's gap recommendations are intended to get you into that 'Goldilocks zone' ' not too big, and not too small. DiBlasi counsels, 'If the top ring end gap is correct, it will end up the smallest amount of ring end gap when fully expanded, and not run into itself. That way it holds in the highest amount of compression in the engine for maximum power output.'
Using a tapered piston ring compressor sleeve in the correct bore size helps ensure the pistons are installed without damaging the rings.Most of the engines you'll encounter utilize a ring package with a second compression ring below the first, to provide additional sealing and another path for heat to escape the piston into the cylinder bore, and from there into the coolant jacket and eventually the atmosphere. As shown above, the desired ring gap for the second ring is often, but not always, greater than the top ring.
'In OEM applications the second ring is tighter than the top ring,' DiBlasi explains. 'It sees less heat, and its purpose is to control oil and be a secondary compression ring for any pressure that gets past the top ring. Since OEM applications are designed to an exact power output, heat, lifecycle, and emission compliance, they run a tighter second ring end gap.'
The situation changes once engine modifications come into the picture. Per DiBlasi, 'We recommend a larger second ring end gap than the top ring for performance and racing engines since they see a wider range of power and heat than OEM. A forced induction engine may see the same power output as when it was in stock form daily driving, but at the track sees 2-3 times the power output it was originally designed for.'
There's a clear technical reason for that extra clearance ' 'We like to see the second ring end gap .001-.002 larger than the top ring so it does not lock in any compression that gets past the top ring,' says DiBlasi. 'If combustion gasses go past the top ring and the second ring gap is less than the top ring, the gas will not pass the second ring. The gas will be forced to return back to the top ring and press up on the bottom of the top ring. That will lift on the bottom side of the top ring, reducing its seal even further.'
As piston rings continue to shrink, proper installation becomes exponentially more important to prevent damage to the ring.Providing a way to control the pressure between the first and second rings is the key to allowing both rings to seal the way they are designed to; because a little bit of 'blow-by' is inevitable, dealing with it is necessary. 'Since the name of the game is keeping as much combustion pressure above the top ring as possible, keeping it seated is required for maximum power. By allowing the second ring to freely let any excessive compression gases keep going, the top ring stays seated. The gas simply goes past it, cools slightly, and enters through the oil drain backs into the bottom of the piston. Your PCV system should be doing its job at that point forward,' DiBlasi explains.
The design of the piston can also play a role in managing the pressure between the first and second rings in order to improve ring seal. DiBlasi says, 'In most cases, we build a groove in between the top and second ring on the second ring land. This groove increases the volume of area between the top and second rings. The increase in volume helps lower the pressure of any gases that end up there.'
Now that we've covered the 'why' of piston ring gapping, it's time to put that knowledge to work. We asked DiBlasi for the main issues people run into, and he gave us some very practical advice, saying, 'There are several mistakes people make when setting ring end gaps. I myself have done it in the past, so it happens to everyone. I will also address ring install problems in general''
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