188 | How to use a ring compressor
Once you’ve got your rings fitted onto your piston and you’re ready to fit the piston into the engine block, you’re going to need to use a ring compressor in order to compress the rings into their ring grooves and allow the piston to be inserted into the bore. If you get this wrong then you risk damaging or even breaking a piston ring. This may also end up scoring your freshly honed bore. In this webinar we’ll look at both tapered style ring compressors and ratchet-style ring compressors and demonstrate how to correctly use them.
- Hey guys it's Andre from High Performance Academy, welcome along to another webinar. In this webinar we are going to be looking at how to use a ring compressor. Now this is a topic that on face value seems pretty simple and pretty dry. However if you don't understand the correct techniques of using a ring compressor it is quite easy for you to end up damaging your ring set. Obviously that's going to be a costly exercise in itself.
But worse still if you damage the ring and you don't notice, it's also possible to end up scoring your freshly honed bores. And if you send the engine out the door without noticing this, you're obviously going to end up with a very expensive come back job on your hands. Obviously that's something no engine builder wants to deal with. So we're gonna have a look at the different ring compressors that are on the market, we're gonna have a practical demonstration here using our Subaru FA20 so we'll see exactly how we can use a couple of those ring compressors. What I would probably consider to be my favourite as well as the most popular ones out there on the market.
As usual with all of our webinars we are gonna be having a Q&A session at the end so if there's anything that I cover off today that you'd like me to go into a little bit more detail on, or anything just generally related to the topic that we're talking about today, please ask those in the comments and the guys will transfer those through to me. So let's start by talking about why we even need a ring compressor. And the reason for that is that we have a certain amount of radial tension on our rings so on this particular piston here which we're gonna be fitting to our Subaru FA20, we've got our ring pack fitted to the piston already. And if we just jump to our overhead shot for a moment hopefully you're gonna be able to get close enough, you can see that the rings actually sit proud of the ring lands. So this means that at the moment it's impossible for us to physically fit the piston down into the bore.
If we try and drop the piston down into the bore, it's simply going to end up with the ring hanging up on the top of the bore because it's sitting proud of those ring grooves. So this is due to the radial tension, essentially the ring exerts radial pressure outwards on the cylinder so when it's not in the cylinder, it pops out wider than our ring grooves. So we're going to need a tool or device that's going to compress those rings into the ring grooves and then allows us to slip the piston down into the bore. So that's the general idea behind a ring compressor, and there are a few different varieties of ring compressor. I don't have all of them here but I'm going to cover off what I consider to be probably the most popular.
So the first one we're going to look at here, this is one we're going to use for our demonstration, is the typical and really popular, universal ratchet style ring compressor. So this is essentially a sleeve that we drop down over the top of our piston. We've then got a key that we locate in the ratchet mechanism and then we can tighten that down onto our piston and as it tightens down it's going to obviously compress those rings. Once we've got everything installed correctly we can then drop our piston down into the bore and then we're going to need to tap the piston gently through that ring compressor until it's located correctly in the bore. Now there's a couple of pros and cons.
Obviously with just about any tool but particularly with this one here, the pro is that it is universal, so we can use it on just about any bore diameter. We just tighten it or expand it to suit whatever our piston diameter is. So that's nice, it's convenient. The downside with it is, or I suppose the other upside is there are quite cheap. You can probably get these for somewhere in the regio of about USD$25 to maybe USD$50 depending on where you're shopping.
There are a couple of downsides though. The first and probably the most serious is that it does take a reasonable amount of force to tap the piston down through this ring compressor, which we'll see during our demonstration. That in itself is not necessarily a problem but if you aren't careful it is possible for the ring to pop out between the bottom of the ring compressor and the top of our bore while we're tapping the piston into the bore. Now if we don't notice that and we keep tapping the piston down it's very easy to bend, damage, or even break the rings. So this is something we obviously don't want occurring.
The other aspect with these and to be fair it could be said for all of our ring compressors is because we oil these during use, we lubricate them with clean mineral based engine oil, often these will be sitting around in the workshop, they do tend to gather dust, dirt, and debris. So it's really important before we go and use one of these or any of our ring compressors for that matter, that we make sure that it properly cleaned. Now my personal favourite is the tapered style ring compressor. This particular one is from ARP. So these are simply a CNC machined aluminium sleeve.
They are larger at the top side than they are at the bottom and the premise behind the use of these is simply that we drop the piston down through the top of it and as the piston travels down through the ring compressor, the rings are compressed by that taper on the inside diameter. So really simple to use. The upside of using these ring compressors is that we need very minimal force in order to locate the piston into the bore and push it through the ring compressor. We can do this just using the pressure from our two thumbs. And because of this if anything goes wrong during the installation process we can just about instantly feel that and we can stop applying pressure and it's almost impossible to damage a ring if we're using a tapered ring compressor.
I won't say it's completely impossible, I'm sure some people out there can find a way to damage a ring with one of these, but it is probably the safest option. Downside with them is that as we can see here this one is listed at 86.5 millimetres. Another one here that is 86 millimetres. And these are specific to an individual bore diameter. So this can get a little bit pricey particularly if you are building multiple engines because you need one of these for each bore diameter that you are expecting to be working on.
Now I just checked before I started this webinar and the price of these can be anywhere as low as about USD$30 and they also go up to over USD$60 for some of the larger diameter ring compressors. So obviously that's gonna start getting pretty pricey if you're looking at maybe buying five, six, or more of these ring compressors. Still they are going to look pretty cheap compared to damaging your rings. So worth considering in my opinion. The last option that we're going to look at is another universal style ring compressor.
This type of ring compressor uses a ratchet tool and a range of different sleeves of different diameters. So the diameter that these will work with is listed on the outside of the sleeve, this one is 86 through to 92 millimetres. So I'm not actually gonna demonstrated this just because I've got a two cylinder engine, two cylinder half of our engine there so it's gonna be a little bit hard for me to demonstrate on three pistons. But hopefully you should be able to understand the premise of use of this is pretty straightforward. We simply install the sleeve around the rings and then using the ratchet, we can tighten it down and it's going to compress the rings into the ring grooves.
Alright so we're going to go through a couple of demonstrations. As I've said, we're gonna use our ratchet style and we're going to use our tapered style ring compressor. But there are actually a couple of steps that we want to go through before we even get to the point of installing our pistons into our bores. And one of the most overlooked I think is the level of cleanliness that we really want to go through when we are building any engine. It's impossible to have our components too clean and particularly when it comes to a fresh hone pattern, that hone pattern is really good at trapping dirt and debris particularly the debris that is created during that honing process.
It can get trapped in that hone pattern and we want to make sure that we thoroughly remove all of that. So the first step we're gonna go through is preparing our engine block. And while it's not essential, my personal preference when we're doing this is to use a white rag. And the reason for this is that it makes it really obvious when we've got that hone pattern truely clean and that's because our rag will come away clean. So we want to use a rag and we wanna also use a brake clean product.
You can also use isopropyl alcohol. Over my years I've tended to always go back to using brake clean. These are available from a variety of different manufacturers under different brand names. But essentially they all do the same thing. It's great at breaking down any oil, it's a good degreaser, and it also evaporates so it doesn't leave any product on the surface.
So let's just go through that and we'll see exactly how dirty our bore is at the moment. So when we're doing this as well, what we want to do is concentrate on moving our rag basically replicating the angle of our hone pattern. So if we can replicate the pattern we're going to do the best job possible of removing any dirt and debris from that hone pattern. And we also want to make sure that we are reaching all the way to the bottom of the bore. Alright so hopefully we can see this on our overhead shot here.
This is a really good indication of exactly what we can see on a white rag when our bores aren't entirely clean. So that's kind of what we've got there. Generally I like to go through and clean the bores at least three or maybe even four times until we're consistently getting that rag coming out completely clean. So once we've done that, the other part that we need to go through is to lubricate the bores. So we want to apply a good coat of lubricating oil and in this case it's always a good idea to make sure that you have a supply of mineral based engine oil in your engine building workshop.
And I've got that here in a little squirty can. The reason it's important to use a mineral based oil here is that while modern honing techniques and modern ring construction or construction materials make it pretty hard now to end up with a set of rings that don't bed in properly, it is still possible if you try really hard and definitely we don't wanna go to the trouble and expense of building a fresh engine only to find that our rings haven't correctly bedded in on that hone pattern. Synthetic oils or full synthetic oils can potentially be too slippery, I know that sounds a little bit hard to believe but they can actually be detrimental to that ring bedding process. So we always wanna start with a fresh clean mineral based oil. So again I'm just going to use a clean white rag here and we'll just apply a little bit of our clean engine oil onto this rag, you can be quite generous with this as well.
And then all we're going to do is use that rag and basically repeat the process that we just went through with our brake clean product. So we wanna apply a generous amount of our engine oil onto that hone pattern right the way around from top to bottom. It's also important to just mention here that if you are cleaning your bores down with a brake clean product you want to lubricate them straight away because particularly in humid areas, you're going to essentially start attracting surface rust onto that freshly cleaned hone pattern straight away. So we wanna make sure that doesn't happen and get some lubricating oil on there. Alright so now we're going to go through the next step.
This particular piston here I've already preassembled our rings onto the piston. In our other piston though we're gonna go through the process of assembling the rings onto the piston so I've got our ring set here which is a JE Proseal ring set. And this is quite simple, it is quite a simple process, but again just like everything else there are a few tips that you need to keep in mind just to make sure that you don't go wrong. What you're going to find is that the manufacturer's instructions which I've got here will give you a little diagram showing the orientation of your rings. So in other words, so we'll go to our overhead shot here and hopefully you'll be able to see this.
So this is designed to show you where you should be aligning your ring end gaps. We want to stagger those when we are installing the rings, just to make sure that we don't kind of have a straight path for any blow by gases to go through. So when we're installing our rings we always want to start from the bottom and work our way up. And we start with our oil ring expander. It's really important when we are installing the oil ring expander as well to make sure that it is fitted the correct way up, again there are some instructions to guide us with that.
So what we're going to do is start by installing our oil ring expander with the end gap on the right hand side of our piston. And we can just gently manipulate this into place, it's actually quite easy to move and we can just spiral that into location. I'll also mention that with our rings we're obviously going to have already gone through the process of gapping the rings and we also have gone through the process of making sure that they are spotlessly clean. So our next step is to fit our two oil ring expanders rails. So these are really flexible so the process of installing these, we don't actually need a ring expander.
All we're going to do is just spiral these into location. And we'll see how that works. So we're gonna start here with our bottom ring and oil ring rail, and I'm just going to locate that where I want the ring end gap. Just try and get it nicely into location. And we're just going to then spiral that around.
I don't want to expand that ring any more than I absolutely need to in order to get it fitted onto the piston. And before we go in and fit our second rail we also want to just make sure that our end gap, or our expander hasn't overlapped. We wanna make sure that that's still located correctly. Alright so we've got our first rail, or ring rail fitted. Now we're going to install our second one, I'm just gonna make sure that I've got my location of our gap matching the literature.
And just move that into location as well. So again you can see hopefully that this process is actually quite straightforward. There's not a lot of pressure, we don't need to try too hard in order to get that oil ring rail located. OK so now we come to our second compression ring and our top compression ring. An important aspect here is that you're going to find that most of these rings, if not all of these rings will have a mark on one side of the ring.
I'm gonna try and hopefully we'll be able to see the mark on our second compression ring here. And hopefully you can see it here, there's a little end that faces upwards, this is the surface of the ring that we need to face up. So we've got our piston located here facing forwards and our second compression ring we want our end gap to be on the left hand side of the piston. Now you can expand the rings by hand, but you do need to be very very careful when you are doing that. It's very easy to end up with the ring flexing and if you're not careful you can bend or damage it.
So here I'm using a ring expander tool, these are really really cheap, so if you are gonna be building engines, it's a really good tool to have. You can probably get these for somewhere in the region of about USD$10 or USD$15 and it's just going to save you a lot of heartache and I know a lot of people will expand the ring by putting their thumbs into the ring gap and expanding it outwards. I can tell you if you're gonna be doing that over a number of rings, you're also gonna get really sore cut up thumbs. So definitely a good tool to have. The other key when we are doing this is we want to only expand the ring as much as we physically need to in order to get it over the piston and located in the ring groove.
So we don't want to over expand the ring, that can end up damaging the ring as well so we've got that located there. I'll just help it into the ring groove there. Always easier when I'm not doing it on camera. So that's our second compression ring fitted, now we're gonna turn the piston over, again I'm just making sure I've got my mark facing upwards. And we're going to repeat the process for our top compression ring.
So I'm just gonna gently lower that down. You also wanna just make sure of course that we aren't scratching the surface of the piston. So just a moderate amount of care is required when we are doing that. OK so we're at a point now where we are ready to install our pistons into the bore. Now in most instances you're also going to have a connecting rod attached to the piston.
You're gonna be installing the piston and conrod assembly. Here for simplicity for our demonstration, we are only installing our piston, just to make things a little bit easier here. So we're going to start by using our telescopic ring compressor here. And of course the first step as I mentioned, we want to make sure that there isn't any dirt or debris on that inside surface. So we've got that nice and clean.
The next step is we're going to be lubricating both our piston and ring pack as well as the inside of our ring compressor. So we don't want to be installing these components dry, it really is important that they are well lubricated. So in this case, generally what I'm going to do here is just use my oiling can and I'm going to be applying just a liberal amount of oil from that oiling can to both the ring pack as well as the skirt of the piston. And this does tend to get a little bit messy. And provided of course your hands are clean, the process there is to just smear the excess oil around those components using your finger.
We've now got our piston ready to go into the bore, and as I've explained I'm just going to do exactly the same with our telescopic ring compressor and just smear that around. Now we're ready to actually install our piston. Again normally we're going to have a connecting rod here as well. I'm just going to drop this down over the piston for the moment. And I'm going to get this ring compressor at least close to where I want it to be.
But I'm not going to tighten it all the way down at this point. And the reason for this is I want to still have a little bit of room, or a little bit of flexibility to move the piston and the conrod assembly down through our ring compressor. And the reason for this is we want to have a little bit of the skirt of the piston exposed, sticking out through the bottom of the ring compressor, and this is going to allow us to easily locate the piston into our bore which is going to help us when it comes to tapping that piston down through the bore. So what we wanna do now is locate the piston in the bore. Just drop that down so it's nice and well located.
And we're going to make sure that our ring compressor is fitted, actually I'm going to just install this for simplicity here around the wrong way on purpose so for those of you who are eagle eyed you will note that I am actually installing this around the wrong way. The reason for this is just simply for our demonstration so I'm not working over the top of myself. So we've got our piston fitted there, we're going to now apply some pressure down on the top of the ring compressor and I'm just going to tighten that down until our rings are properly compressed. Now the problem we're got is that there is a reasonable amount of tension on the piston and the rings and there is a bit of friction as a result. So what we're going to need to do is actually apply a little bit of force to tap this piston down through the ring compressor.
And in order to do this, what we want to use is obviously something that's not going to end up potentially marking or damaging the crown of the piston. A good option for that is the end of a wooden mallet. Obviously assuming that the end of the mallet hasn't got big bits of steel or swarf embedded in it. Also another option would be the end of a plastic mallet. So basically something we can apply a little bit of force to but we're not going to end up risking damaging the crown surface of the piston.
The other key when we're doing this is we want to make sure with our other hand that we are applying a reasonable amount of force downwards on the top of our telescopic compressor and this is going to help prevent that ring pack jumping out. Alright so let's go through that now. And generally you're going to end up with a nice satisfying click as the rings drop into place and our piston is located in the bore. So we've gone through there, we've got our piston located. And from here we can now quite easily move the piston down the bore using our thumbs.
It's always a good idea to just inspect the sides of the bore there, particularly in line with where our rings are located. Just to make sure that we aren't seeing any scoring. Which could indicate that we have damaged the piston. So we've looked at our first example there, we are now going to go through and perform another demonstration here using our tapered ring compressor. This is hopefully gonna be much quicker and much easier as well which is why we use the tapered ring compressor.
This is gonna be a perfect time to ask any questions that you may have. Alright so in this case we've got our 86.5 millimetre tapered ring compressor. I'm just gonna go through and make sure that that is nice and clean and we're going to apply a generous amount of lubricating oil to the inside of that tapered ring compressor. Now we're gonna go through and repeat the process that we looked at with our other piston, we're just going to apply some lubricating oil to our ring pack as well as the skirt of the piston. Just generously share that around using our finger there and now we can install the piston into our tapered ring compressor.
Normally because we're going to have a connecting rod fitted to the piston, this becomes a little bit simpler. We can use the rod to guide the piston into location. And we have our piston now located in our ring compressor, again just like with our ratchet style ring compressor we want a little bit of the skirt located out the bottom of the tapered ring compressor. We can now locate our piston into the bore make sure everything's square. Again we wanna apply a little bit of pressure downwards on our tapered ring compressor.
But you're gonna find that this time, you can push the piston down through the ring compressor really easily, just using the pressure from our two thumbs. So that's as quick as it is as well, it's really really easy to use. Makes installing a large number of rings or pistons into engine blocks very very quick and easy. And again because I've used so little pressure in order to install that piston, I can have the confidence that there's no chance that I've damaged the ring pack. Just the same though it's still a good idea to just inspect the surface of the bore and to make sure there that we haven't ended up with any scoring on our bores.
Alright so that brings us to the end of our demonstration. If you do have any questions, please ask them and I'll see what I can do. OK our first question comes from Craig who's asked is there a limit to the amount of times you can install and uninstall the piston? If you're talking there Craig about during a dummy build, I mean essentially as long as you aren't rough with the piston, you're not mishandling it or risking damaging it then absolutely not, you can install and remove the piston as many times as you want. It's not actually going to wear the piston or damage it. So you're absolutely fine there.
Obviously if you are a little bit slap dash with your handling of the piston though, every time you handle the piston it does give you another opportunity to potentially do some damage. David has asked, when staggering rings on the piston, where are you placing each of the rings' ring gap? OK so again this really comes from the orientation diagram that is provided by the ring manufacturer. And I think there's also, it's worth just mentioning here that while yes we are gonna go through the process of aligning the rings for our very first start up in conjunction with the manufacturer's recommendations, it's also important to understand a point that is overlooked I think a lot, that in operation the rings actually will rotate on the piston. So you're going to find that if you run the engine for 5000, 10000, 20000 miles and you pulled those piston out, the rings aren't gonna be exactly where you put them. Basically what we wanna do is avoid aligning the ring end gaps so that there's a nice straight path for any of our blow by gases or combustion pressure to escape through.
Wanna give the, make it a little bit harder for those blow by gases to make their way past the ring pack and into the crank case. John has asked, what does it mean when the rings are seated when breaking the engine in? OK so that's a term that is used to basically say that the rings are sealing correctly. So what you need to understand is with any engine that has been freshly machined, we're going to have high spots and low spots on the cylinder walls, particularly with our hone pattern that is developed specifically for helping those rings seat. Likewise the rings themselves are going to have surface imperfections. So the bedding in process when we are running in a new engine is all about trying to wear down the high spots, basically even everything out, so we've got as good a seal as we can possibly achieve between the rings and the cylinder wall.
So the better we do here, and this comes down to our machining, our materials choice as well as our running in or bedding in process, basically the more power we're likely to get out of our engine, as well as the longer we can expect out of it in terms of a service life. Terry has asked ring gap differences for naturally aspirated boost, nitrous, or nitrous and boost. Probably a little bit off the topic of our webinar today but I'll just touch on it briefly. We do have webinars on this specific topic. But essentially what you need to understand is when we are choosing a ring end gap when we're at room temperature here and we are building our engine, is what we're really trying to do is anticipate a ring gap at room temperature that is going to result in a minimal ring gap once the engine is being driven hard and the ring has expanded due to the heat in the combustion chamber that it's being exposed to.
Obviously we don't wanna go too far, if the ring expands too much and the two ends butt together then at that point the ring has nowhere else to expand except for outwards, that can end up with the ring seizing or nippIng up in the bore and that's gonna be a fairly catastrophic engine failure if that occurs. So really to answer your question there more specifically there Terry, what you've gotta look at is the heat that is being produced there. So all things being equal, a naturally aspirated engine versus a turbo or supercharged engine, with the forced induction engine we are physically forcing more air, hence we're adding more fuel into the combustion chamber. This is getting a larger combustion event compared to the naturally aspirated engine and hence we can expect more heat in the combustion chamber. So it's not uncommon to increase the end gap of our rings by somewhere in the region of maybe half a thou to one thou per inch of bore.
It's really important to note that is per inch of bore not overall. Personally in my own engines that I build I treat nitrous and forced induction very similar. Essentially nitrous is just another way of introducing more oxygen. For exactly the same reason that I target similar air fuel ratios between nitrous and supercharged or turbocharged engines as well. So don't really split those up.
Another aspect that I'll just quickly touch on there as well, fuel type and the application of your engine or in other words how it's going to be used. Whether it's a road car engine, drag, or circuit, will also impact on your ring end gaps. Cole has asked how do you recommend setting the rings during break in, I hear so many different opinions? Yeah Cole absolutely there are so many opinions out there. And a lot of people try and make out that it is a lot more complex than it is. It's really quite straightforward and quite simple and the great news is that you don't need to do 1000 or 2000 miles of gentle driving to break in your new engine.
That may have been the case many years ago however our modern ring construction techniques as well as the honing processes that are used have greatly simplified this. So generally what we wanna do is use moderate amounts of load, we definitely don't wanna be going straight to the rev limiter and driving it like we stole it. We wanna be using moderate amounts of load and low to moderate amounts of engine RPM and the important point is that we want to cycle between periods of moderate load, so this is where we're accelerating lightly, and then backing off. And the reason that we are trying to do this is that the radial tension outwards on the cylinder wall itself isn't actually what makes the rings seal. It's the combustion pressure that gets in behind the ring and forces it out, and this is what actually makes the rings seal.
So when we use a moderate amount of load we've got a little bit more combustion pressure to force that ring out against the cylinder wall. Now that helps the bedding process, you could kind of think of that hone pattern a little bit like a very fine file and this helps the ring to bed. Of course the downside is that when that hone pattern is fresh and we're just bedding in our rings, it's creating a lot of friction and causing a lot of heat. So we want to temper our moderate load running with periods of light load. And when we back off the throttle and we use lighter load, this reduces that pressure forcing the rings out.
It also can help draw cooling oil back up bores to help wash away the debris that's created and also cool down our rings. So it's a case of constantly changing between moderate load and light load. We're going to start at relatively low RPM and then build up as we go through the running in process. I generally do this on the dyno and it's much quicker than most people think. I'll generally run and engine for between maybe 60 and 100 kilometres, then we'll change the oil and we'll get straight into tuning.
And there will be a small amount of continued running in that will happen over the following maybe total of 200 kilometres but basically once you've got to that point it's all downhill, your engine is as run in as it's ever going to be and you may as well start using the engine. Jonathan has asked, how does having vertical or lateral gas ports on a piston affect the ring life? Great point there Jonathan, so these gas ports as they are know are all about actually helping with what I was just talking about, allowing a direct path for that combustion pressure to get in behind the ring and force it out. I actually think, I'll just see, I think I've got a piston here with vertical gas ports, yes I do. We'll just see if we can get this under our overhead camera here. And this is a piston from a 4G63 drag engine and we can see around the outside of the piston crown we've got these little vertical holes.
And these drill down and get straight in behind our top ring and help force it out. So the problem with these gas ports, particularly the vertical gas ports, is they are really only suited to short run engines, particularly those that are running on alcohol based fuels because they run much cleaner. If you're running on a pump based fuel the carbon build up on the crown of the piston is going to pretty much fill those holes in and render them useless under fairly short running times so it's not something that's really going to be useful for a road car engine. DB500 has asked I've heard that it's undesirable to have too much oil when lubricating the piston and the rings before installing them into the block, what are the penalties of using too much oil? Are there alternatives to motor oil like grease or dry lubricant a mineral or synthetic? Look I honestly put that down to just a kind of urban engine builder myth. It's certainly in my experience not an issue.
Clearly when we've got our engine built, we don't want the top of the piston swimming with oil because all of that oil is going to end up burning off during start up and it can end up forming carbon deposits. So yeah we don't want the top of the piston swimming with oil but all of that lubricant that you saw me apply to the ring pack, that's honestly not a problem. During the first cranking over process where we're cranking the engine to initially get oil pressure up, a lot of that oil on the cylinder walls is going to end up getting scraped off by the oil control rings and get returned back into the crank case anyway so little bit of common sense prevails there. Alright guys that looks like it's brought us to the end of our questions there, so thank you for everyone who has joined us, thanks for all of those questions we've got there, some great ones. If you do have any more questions that crop up after this webinar has aired, please ask them in the forum and I'll be happy to answer them there.
Alright thanks for joining us guys, and we look forward to seeing you all next time.