206 | Valve Springs - What You Need to know
A camshaft upgrade is one of the most common ways to improve engine performance, however there’s more to a cam upgrade than just fitting the camshaft. In this webinar we’ll discuss valve spring options, and find out what you need to know in order to choose suitable springs and install them correctly in your engine.
- Hey guys it's Andre from High Performance Academy. Welcome along to another one of our webinars. This time we're gonna be talking about a topic that I think is often overlooked by engine builders and this is the selection of our valve springs. Now I wanna be really clear right here at the start of this webinar, 'cause I know I'm gonna probably be getting a few questions along these lines towards the end. This webinar isn't designed to teach you which valve spring is going to be right for your car.
As you're going to find out during the webinar, there is literally hundreds of different aspects that really need to be accounted for in order to choose the correct valve spring that's gonna suit your particular engine and your particular camshaft. And this is more about learning what those differences are, learning about the differences between single valve springs, double valve springs, beehive valve springs et cetera and also learning how to decide or choose the correct valve spring based on your cam manufacturer, that's really the key point. As usual though we will be having questions and answers at the end. So while hopefully I won't be getting inundated with what valve spring should I be running in my application or what seat pressure should I use for this? I'm not gonna be able to answer those for the reasons I've just given you. If you do have generic questions around this topic or anything related to it, those are gonna be perfect, chuck those in the chat and we'll get to those at the end.
So I think the first thing to consider here is the valve springs get an incredibly hard life. They are responsible for opening and closing the valves and making sure that the valve stays under control. So if we don't have the correct valve spring here, we can easily end up with catastrophic engine damage, we can end up with valve flow, we can end up with valve bounce which we're gonna talk about in more detail. And particularly at very high RPM when we may have very very tight tolerances around our valve clearances, it doesn't take much of a problem to occur in our valve train before we end up with some pretty nasty damage happening. So nobody wants that to happen.
Just to put some numbers into perspective as well 'cause I know that when it comes to engine operation it's really easy to lose track of exactly how fast every thing is happening inside your engine. If we look at an engine that is operating at let's say 8000 RPM, not uncommon now even as a factory rev limit for a lot of multi valve late model Japanese engines. That's really really low if we're thinking about multi valve Japanese sports bikes for example but at 8000 RPM our valves are opening and closing 66 times per second. So that hopefully gives you some perspective there. And under these circumstances, we understand that our camshaft there is opening the valve off the valve seat, accelerating it, it's lifting it through to peak lift, then it's slowing as it goes across the nose of the cam and then it's gently closing it down onto the valve seat and everything there, both with the cam profile as well as the valve spring has to be absolutely perfect.
Now again just to give you some sort of generalisations here across what these valve springs may be doing, again, hopefully this is gonna give you some indication that we can't have an across the board answer or rule of thumb for every valve spring. So if we are looking at a typical small capacity engine, maybe such as a four cylinder Mitsubishi 4G63 turbo engine, we may end up with the valve springs providing a seat pressure, so this is the pressure that's actually setaing the valve or holding it closed when it's not open at all, somewhere maybe in the region of 60 to 100 pounds. And then depending on our valve lift et cetera, over the peak opening of our valve, we may end up with an opening pressure of somewhere in the region of about 200 pounds. So that's for a small valve multi valve engine. However if we take that to extremes and we look at the likes of Pro Stock.
Now this is kind of a moving ballpark here because the technology in Pro Stock is always changing. Also it's unlikely we're gonna get any really accurate answers because the people developing these Pro Stock engines are incredibly cagey. But on those 500 cubic inch engines, it's not uncommon to have seating pressure somewhere in the region of 500, maybe 550 or more pounds. So in contrast to our small valve engine, 60 to 100, massive massive difference there. And they may also easily have in excess of 1000 pounds of pressure on the valve when they are at peak lift.
Now granted with a Pro Stock engine, they may be running somewhere in the region of one inch of lift or more, again don't take these numbers as gospel, this is just what I can find out, I certainly don't build or develop them. Now the important things to understand here is when you're dealing with an engine at that level, particularly due to the incredibly high pressures involved in the valve train, these valve springs don't last long. So in Pro Stock racing, it's common that after every pass down the strip, the valve spring seat pressure will be checked, and basically the crew chief or the engine chief there will use that number as a guide as to what the life of that spring is likely to be. And generally they will drop immediately and then sit there for a little bit and then they'll start to drop away in terms of their pressure. So the valve springs may be replaced after somewhere in the region of 5 to maybe 8 passes down the strip and these are generally either double or triple valve springs, also very very expensive so it's a pretty pricey consumable.
Alright so there's some generalities around valve springs and hopefully why we can't, understanding why we can't use numbers from one particular engine into another. So we obviously need now to consider the factors that will influence the valve spring choice that is gonna be suitable for our engine. And this comes down really to four main aspects. First of all we need to consider the engine RPM. And the reason for this is as we increase our engine RPM, the forces involved there increase at the square of our RPM increase.
So if we double our RPM we're not just doubling the forces involved, they're actually going up at the square of that so it's a significant increase in all of the loads and forces involved in the valve train. So even if you're increasing your engine RPM only by 500 RPM, it doesn't sound like much but that actually can have quite a big impact if your valve springs were only marginal at your existing engine RPM. The other one that goes hand in hand with this is the agressiveness of our cam grind. And this really comes down to the amount of valve lift that's been provided and how quickly the opening ramp and the closing ramps are lifting that valve up off its seat and accelerating it and then decelerating it back and closing it back onto the valve seat. The faster we wanna lift that valve, generally that means that we're going to need more spring pressure in order to cope with that and maintain control over our valves during operation.
We also do need to factor in boost pressure here because particulary on the intake valves we've got that boost pressure acting on the valves trying to force them open. It's easy to overlook though that this is also going to involve a significant amount of pressure on the exhaust side as well trying to force our exhaust valves open. Now of course under most circumstances during the engine operation, they are also fighting, that pressure on one side of the valve, is fighting against the pressure inside of the combustion chamber so we do need to factor that in, but boost pressure definitely is a consideration we take into account. And then the last aspect that I wanna deal with here is the size and specifically the mass of our valves. So I just wanna give you a little graphical demonstration of that here.
So let's just head to our overhead cam. I'll just get our little scale set up. So what I've got here is a valve from our Subaru FA20 so I'll stick that on there, pretty typical multi valve, four valve cylinder head style valve. And we've got a mass there of 45.7 grams. Now I'm going to put an intake valve here, this is a factory valve off a GM LS1.
So we can see that we've got a valve mass there of 99 grams. So we're more that double the mass of our small four valve intake valve. So pretty much to be expected though, we've got a two valve LS1 versus a four valve FA20 cylinder head. Obviously to flow air with the two valve engine we need a larger diameter valve and just to give you a bit of a side by side indication, that's our two valves there. So massive difference in our valve head size and obviously that equates to the weight.
But of course when we've got larger valve mass we do need to take that into account because we need to control that mass and this again really, the mass of the valves combined with the RPM and the cam profile, this is the considerations we need when we are choosing the correct valve spring for our application. So when things go wrong, we've got two issues that, typical issues that come up. The first is valve bounce and as its name implies, this is simply when the valve bounces back open after it contacts the seat. So as the valve is being closed, basically it will bounce back off the seat and bounce open so we'll lose control of the valve there. And this has a dramatic influence on our engine performance.
Generally valve bounce is going to be caused either insufficient spring pressure with our valve springs or alternatively it can be a result of a closing ramp on our camshaft that's too aggressive. Now I do have a video of this and I'm going to apologise in advance, this is from Comp Cams but this is possibly the worst video I've ever seen on the internet in terms of quality. I think it was filmed potentially with a potato but hopefully if you can bear with us here and what we're looking at here is the valve spring, this is on a Spintron machine which allows us to see exactly what's happening during the valve train cycle. We'll just play this for a few seconds and what we're looking for here, I might have to play it a couple of times so we can explain it. We're looking at what happens immediately after the valve closes.
So what we see here is at the top we've got our rocker arm. This is what's actually actuating the valve. And obviously what we're going to see is as the valve opens, the rocker arm moves down, opening our valve. What I want you to look for specifically is when that valve comes back up, when the rocker arm comes back up, what you're going to see, and if you look particularly around this area here with the roller at the end of the rocker arm, you're going to see it vibrate backwards and forwards, up and down. So let's just try playing that again now that you kind of know what you're looking for and we'll see what's actually going on here.
So hopefully you can see that's happening right there and again now. So that's that valve bouncing backwards and forwards, open and closed on the seat. Alright so I'll head back to my notes now. So that's what valve bounce is. Obviously we want to make sure that we avoid that at all costs.
As I've said, it's going to have a dramatic effect on our performance but it's also going to beat up really hard on our components and our valve train. So if you run an engine into valve bounce, not only are you going to be hurting your performance but if you do it for long enough you're going to risk a pretty dramatic failure. The other aspect that we see here is valve float. So this is where the valve train or the cam, the rocker, whatever your valve train actually looks like, loses control over the valves. So it basically, it's no longer in contact with the cam profile and the valve is free to flow.
Now this presents a pretty big problem because this will happen generally as the valves are closing and if the piston is chasing the valves closed and all of a sudden the valve is not where it's supposed to be, and it's further open than it should be, we risk the situation where our piston is going to end up punching the valve and that again can result in catastrophic engine failure. So our valve float issue, this comes down to again our spring pressure. This can be also combined with engine RPM and our cam profile. So these things all go hand in hand and one of the key aspects here is obviously you need to start by making sure that you are dealing with a cam profile that's been correctly specified for that you want to do. Really everything comes back to dealing with some professionals here with both cam and valve spring selection to make sure that you've got parts that are gonna be suited to your application.
Alright so when it comes to our valve spring choices there are a few options here and I wanna go through a couple of them. So the first one we're going to have a look at here is our single spring. So if we go to our overhead camera here, this is a single spring upgrade that we are actually going to be putting into our Subaru FA20. Nothing particularly exciting and actually before I get scolded by the internet here, I will also mention that when we are dealing with valve springs, it's always a good idea to wear some protective gloves. The reason for this is it does stop the oils and acids from your hand actually damaging the protective oil, or removing the protective oil from the surface finish of the springs and this can end up resulting in corrosion beginning which can also result in premature failure of the springs.
So you'll note that I'm not doing that. I'm prepared to take that risk. I'm just basically explaining the way you would do it when you are building an engine, obviously here we're just running a demonstration webinar. It's gonna be a little bit weird if I'm standing here wearing a pair of gloves. So do as I say, not necessarily as I do.
OK so our single valve spring there, the advantages are that they are pretty damn cheap, the other point I'll make is not only is this a single valve spring, you'll also see that it is parallel from top to bottom. So that's important, we'll get into why that's important as we look at some of our other valve spring choices. So they are cheap, they're readily available, and these are probably pretty well ideal for a mild cam upgrade which we're likely to be seeing in a street car. So in most instances, particularly with a four valve engine where we don't need the sort of seat pressures that we are seeing in some of these two valve engines like the LS1 that we looked at, this can be more than sufficient for our application so it's gonna be cost effective and easy to fit. However as we move up in our cam profiles, we start going for a more aggressive cam with more lift, it can get quite tricky in a parallel single spring like that to maintain good control of our valve train.
It's almost certain that we're going to need to look at another option. So the first of these is to look at a double valve spring. So I've got one of these here, we'll just put it side by side. It's gonna roll away which is perfect. And then we'll also grab another one here and we'll disassemble it so we can see what we're actually dealing with here so this one comes from Supertech.
So there is our double valve spring in component form. So the double valve spring, basically one of the killers of our valve train or our valve springs is harmonics in the spring. And this is a big problem. What we find is that with all valve springs, we're going to have a harmonic frequency at which the valve spring will resonate. And if we run our spring at that resonant frequency it's going to end up becoming damaged very very quickly.
Now with a double valve spring system, it provides two advantages. First of all we've got two springs there, so both of them are adding to the spring pressure being exerted on the valve train. But also the two springs have separate harmonic frequencies. So it kind of splits that up a little bit and just provides a more reliable result there. So the downside with these is that they are a little bit more pricey.
Generally you're also going to have to run a specific retainer with these to correctly locate the inside or the internal valve spring. And you're also probably going to need to run a specific base. So the double valve spring kits can get a little bit more pricey. As I mentioned earlier when we were talking about the Pro Stock engines as well, at very high end with valve trains, it is also common or possible to use triple valve springs. Not very common for anything outside of professional high end motorsport but just to mention that yes they do exist and it basically builds on the idea of double valve spring and as you can imagine, just takes things one step further.
Now these days we are seeing less and less double valve springs in the road car and semi professional motorsport level because these are now being replaced quite frequently with what is called a beehive valve spring. So what I'm gonna do is get one of these beehive valve springs and I'll lay it side by side with our single springs so you can see what we've got going on here. So this is a beehive valve spring for our LS1, see if I can stop it rolling around. Perfect. And the name beehive just comes from the shape of the spring.
So what we see is that it tapers towards the top. It's no longer parallel. So with the beehive valve springs, they're also made, as is common with our valve springs these days, out of an ovate or oval wire profile. So this is just all about again just reducing the harmonics or changing the resonant frequency in that valve spring to make it last longer. So there are some advantages with these beehive design valve springs which is why they're now becoming so common.
One of the advantages is because of the way they are wound, and we see both the tapered shape to the valve springs as well as the fact that the distance between the coils changes as we move from the bottom to the top. Basically this means that the resonant frequency changes through the valve spring and this allows the centre of that valve spring to dissipate some of these harmonics without doing damage. Now the advantage from our perspective though is this allows better valve control with less spring pressure. And of course the more spring pressure we've got in here, the harder our valve train is working, the more forces are involved and the more we're beating up on all of our components and also this has a tendency to sap or affect our engine performance or power as well. So reducing that spring pressure gives us less wear on our valve train components, we've got a lower spring mass as well, and the other advantage as well, as we can see at the top here where our retainer goes, we're going to end up with a smaller diameter retainer, or the potential for a smaller diameter retainer and this in turn reduces the mass of the retainer.
So we're further reducing the mass of the entire valve system. So if we can, let me just see if I can get this to the right spot. Alright if we can jump across to my laptop screen, we'll have another look at Comp Cams' video here and this shows the effect, basically same engine, same test conditions, actually a higher RPM but this time with the beehive style valve spring. So I'll just run this a couple of times again. So the point here is the first test that we looked at was run at 5200 RPM, they've now actually stepped up their test speed to 6000 which would typically cause more problems with a valve spring that was already causing valve bounce.
So the important point to note here is again looking at the top of the rocker, as the valve closes it's rock solid this time, we'll just play that one more time. And while you're watching that as well, also note that there is a harmonic occurring in the centre of the valve spring, basically the valve spring is absorbing or wobbling, it's not making that valve bounce back off the seat so let's just play that one more time. Alright so there you go, there's the beehive style valve spring. And generally the beehive valve spring is going to be the go to for most applications where they are available, they're gonna do most things that a double valve spring kit would do with probably more often than not less cost, less mass and improved simplicity. So there's not a lot of downsides there and a lot of upsides, if they are available to suit your cam, that's generally the way I would personally be going.
Probably only really high end very high RPM race motors where we would still consider double or maybe triple valve springs. Probably something I should have dealt with a little earlier in there but I do wanna talk about a couple of the terms that you're gonna hear when we are talking about valve springs. So the first two that I've already actually talked about is the seat pressure and then there is the open pressure, also often referred to as pressure over the nose. And this simply really defines the pressure that the valve spring is going to exert when the valve is closed and then the open pressure or pressure over the nose is when the cam or valve is at maximum lift. So those are two of the key metrics that we do need to understand there when we are choosing valve springs.
Now our seat pressure will also be defined at a specific installed height. So these two go hand in hand. The valve spring as we compress it more, provides more pressure, probably not a lot of rocket science in there, it's just like any spring that we deal with. So in order to achieve the manufacturer's recommended seat pressure, we do need to make sure that the installed height is correct. So this will be specified by the spring manufacturer.
Let me just see here, probably, so I'm not gonna be able to show you on a camera here but on our valve springs to suit our Subaru FA20, the information that we need is right here. Basically it says that we'll achieve 68 pounds of seat pressure with a 32.6 millimetre installed height. Now it also says here which is important information to understand, with these particular springs, they are designed to use the OEM retainer and base. That is not always the case, and these will give 166 pounds of opening pressure at 11.5 millimetres of lift. Last point there is the maximum lift for these valve springs is 13 millimetres.
So that brings me to the last point as well, we'll talk about our maximum lift shortly. So with our installed height, what we're looking at here, if we go to our overhead camera, we are simply looking at the height between the top of our valve spring and the bottom of our valve spring. Not particularly complex there. In a lot of applications this is reasonably easy to measure directly with a pair of digital vernier calipers. In some engines this can be a little bit more tricky to actually get access to the side of the valve spring so we can get down there and measure.
But it is important because otherwise if we don't know that our installed height is correct, we may not be achieving anything like the manufacturer's recommendation there. So what we're going to do is obviously make sure our installed height is correct, giving us our manufacturer's recommended seat pressure. From here we need to consider the last aspect which is our maximum lift or in other words at which point our valve spring will become coil bound. So essentially if we compress the valve spring too far, we're going to get to a situation where all of the coils are contacting each other and our valve spring becomes solid. Now clearly if we get to that situation, our valve spring's not gonna be able to do its job anymore and we risk doing a lot of damage to our valve train and to our engine so we need to be very careful and make sure that we have got sufficient clearance there.
So again with our Kelford valve springs for our FA20, as we would expect with most aftermarket valve springs, they give us an installed height and then a maximum lift. So we know that if we've got it at the right installed height with these particular valve springs, we can run a maximum of 11.5 millimetres of lift, you just need to make sure that you are within that range. Now an interesting aspect here is that most race engine builders will actually try and run the valve spring pretty close to coil bind. And the reason for this is, hopefully as you saw during the Comp Cams video there, we do tend to get, for want of a better technical term, a bit of wobble occurring in the centre of our spring there. And if this is left to go unchecked, it can result in more premature failure of our valve spring.
So of course if our valve spring is compressed really really tightly, there's much less room for that to occur. And basically the valve spring tends to be more under control. A rough rule of thumb there is we want to make sure that we're maintaining at least around about 60 thou or 1.5 millimetres from coil bind. We don't wanna run too close there. Right we are going to be moving into some questions and answers really shortly so again if you do have any questions about this topic, please ask those in the chat.
I also should mention here that when we are choosing our valve springs, we want to run the lightest spring pressure that we can get away with that's still going to provide good control over the valve for all of those reasons I've already mentioned. Obviously as we increase our spring pressure, we're going to be putting a lot more load and a lot more force through our valve train. And for this reason, you'll see if you ever get the opportunity to see a push rod out of a Pro Stock engine or anything operating at that level, not to mention also the rocker system, everything looks like it's built to handle the huge forces involved, it's exactly right, they're massive diameter push rods, the rockers are also over engineered, they're really really rigid to resist the potential for them to actually bend instead of doing what they're supposed to do and opening and closing the valves. Alright we're gonna just talk about a couple of aspects here to do with actually changing valve springs. This is an area that I know I get a lot of questions about.
A lot of people think that in order to change valve springs, if you've got an engine that's already built, you're going to need to pull the cylinder head off or cylinder heads off the engine. And that's not always the case, 'cause obviously this is going to be a common upgrade, particularly we see this on a lot of V8s where the cam change on its own can provide massive improvements in performance without any internal changes beyond the actual cam. So it's a big time saver if we can change the valve springs in place. So this can be done with a little bit of care. And what we need to be doing here is using a particular valve spring compressor.
For a lot of the V8s like the LS market, there are off the shelf valve spring compressors that just simply wind down on a pedestal in the cylinder head and compress the valve springs, allowing you to move the retainers. Now a trick with doing this though is that in order to keep the valves closed, you do need to provide compressed air into the cylinder during this process. That'll just keep the valves closed and allow you to actually compress those springs down. Now if you are gonna be doing this though, one of the common mistakes is that people will end up losing one or both the retainers or collets. So let's just have a quick look at our collet so we know what we're dealing with here.
Yeah these little guys here, they're pretty tiny and they are really easy to end up losing in your cylinder head. Now generally while you'd think on face value that you've got less chance of winning the lottery, than one of these making its way down and oil gallery into the sump, inevitably in my experience, that's exactly what happens every damn time. So if I am ever changing valve springs in place, what I'm going to do is make sure before I remove my very first valve spring, that I have taken some rags, and I have managed to poke rags down in all of the oil galleries, all of the oil returns so there is no chance of any of those collets or little retainers there making their way down into the sump. 'Cause that's gonna cause a huge waste of your time and you'll probably end up wishing that you had decided to pull the heads in the first place. So that's probably the key point when you are changing valve springs in place, make sure you use pressure into the combustion chamber to lift the valves up and make sure that you block all of the potential oil galleries and oil returns so that if one of those collets does go missing, you know that its' not gonna end up in your sump.
Another little trick when you are removing them as well, it's always a good idea to use a little magnetic tool like this and if we just go to our overhead quickly. Again nothing particularly magical here, you can just put this right up next to the valve head as you are compressing the valve spring and this will just allow it to quickly pick up those collets straight away as soon as they become free from the valve. Obviously getting them out is one thing, putting them back together is just as tricky. And actually that's probably a good point to show you. When I am installing the collets, I'm going to use an engine assembly lube like this, essentially for lubricating those collets, just a small dollop of that engine assembly lubricant on the end of a jeweller's screwdriver.
It will make the collets stay put and particularly once you do get the collet located in the little groove on the valve, the collet will stay on the valve. So it's always a good idea to use that, it's just gonna make your life go a lot easier, make the job go a lot smoother. Lastly here as well, I'll just mention when you are changing valve springs, often you will need to change the valve seats and the valve retainers. If you are assembling an engine and particularly if you've got an aluminium cylinder head, understand that the valves don't run directly on the aluminium, there will be a spring seat that sits underneath those. Quite often, particularly if you are switching from a single valve spring to a double valve spring like we've got here, you will have a particular valve seat that just does a better job of locating that in a spring and quite often the other tip with this is in order to fit the new valve spring base, you may end up needing to remove the factory valve guide seals.
Now if you do need to remove those seals, these aren't reusable. When you remove them from the valve guide, they are gonna be damaged or destroyed. So it's always a good idea to think ahead, understand if you do need to replace them then have those on hand so you can do that as part of the valve spring installation. And this is also a good time if you're getting down to that point, if you've got a high mileage engine, it may be a good idea for a relatively small investment to change those valve guide seals out anyway, give yourself the best chance possible of giving your engine a long and healthy life. Alright we will move into our questions and answers now.
Again if you've got any further questions, please ask those in the chat. Daniel has asked, are beehive style springs being produced more commonly now? If so, who makes them? Yeah they are, there are a variety of manufacturers. There's probably actually only a handful of people making the springs but of course we've got a variety of cam and cam component suppliers. Right here we've obviously got our Kelford cams. They're supplying valve springs which use pack alloy.
They're not actually making those springs themselves, they're just sourcing springs that are suitable and depending on the application they'll be able to provide springs from different manufacturers. And then we've got our Supertech product over here as well that we've already looked at. So there really are a variety of manufacturers of these components. I couldn't list all of them and generally it's just gonna come down to dealing with your cam manufacturer to find out what's gonna be suitable, they'll be able to recommend what's gonna work for you. Michael's asked, what is the effect of too much spring pressure? So basically you're just going to be putting undue wear and tear or unnecessary wear and tear on all of the valve train components.
You're going to be putting wear through the rocker, or depending on what obviously your valve actuation system is, through the rocker system or the bucket interaction with the cam, this could prematurely wear out your cams. Of course because of that excess pressure as well, you can end up seeing a reduction in engine performance as a result. Basically it's just harder to turn the cam, to lift and close those valves. John has asked, on upgrading valve springs, do the retainers need to be upgraded or is it dependant on the valve spring, the rate, the spring, the aggressiveness and is it OK to us OE retainers? Actually a good point there, I didn't really touch on the retainer as much as I probably should have so I have got a couple of examples here. So first of all with our valve spring upgrade for our Subaru FA20, these are only a modest upgrade.
They are actually only gonna be used in our instance for a stock cam. We're not changing the cam profile, we're not changing the RPM range. It's simply because we've taken a naturally aspirated engine that in stock form has a very weak valve spring and we've now added boost to it so it's just a safety precaution more than anything. And these are designed to work with the stock retainer. So if we look at our overhead camera here I'll see if I can just show you this.
It's important to make sure, there is a step here, let's see if we can have a look at that in a little bit more detail. And we can see our step there on the edge of the retainer. And we wanna make sure that that just locates accurately on our valve spring. On the other hand, with our double valve spring kit here from Supertech, as I've mentioned a couple of times, these are a little bit more involved because we need to locate the inner spring as well. So we've got a specific retainer from Supertech here and as is common with aftermarket retainers, these are manufactured from titanium, reduces the mass of the retainer, and it is actually often quite noticeable although I think a lot of this does come down to a bit of marketing hype.
And as you could imagine here, we'll go to our overhead shot, we've got an extra step on our retainer and that just locates on our innter spring and our outer spring equally. So you will be able to purchase a spring that is either suited for the factory retainer or a spring that is going to require its own aftermarket retainer, in that instance the valve spring manufacturer will be providing that for you and in some instances where you do have an option, you may have the chance to go to a titanium retainer just to reduce a little bit of mass in the valve train there. Rashid has asked, what type of springs are best for a 4AGE 20 valve. Pretty much as I've mentioned here, talk to your cam manufacturer to make sure you've got a valve spring that is suited to the cam and what you're doing with your engine. Daniel has asked, what about conical springs? Actually good point there Daniel, I haven't really touched on conical springs, so conical springs, a little bit like a beehive style valve spring in that they form a cone shape from the wider base to the top.
The conical spring, not one that I've dealt with much. There are some perceived advantages over a beehive valve spring. But essentially the premise behind the conical spring, quite similar to a beehive valve spring there. Jamie has asked, thoughts on upgrading springs and retainers but leaving stock cams for instance a B and K series Honda engine. Look unless you were doing something like adding forced induction, or you were planning on revving the engine a lot harder than stock, which to be fair isn't gonna work with a stock cam anyway, there's probably little advantage.
The retainer, you could get some advantage from going to a titanium retainer but in all honesty I think you'd be really hard pressed to pick that. So if you were gonna be running very high boost through a B series or K series and you were going to retain the stock cam, I know a lot of people do that, under those circumstances, yeah a valve spring change may be necessary, for naturally aspirated or mild boost, generally not a requirement. Jay has asked, assuming the engine is built, is valve spring pressure and oil pressure the only things needed to be considered when bringing the engine above factory red line? I.e. the factory red line is 8000 RPM, I wanna run to 10. No definitely not, there are a raft of things you need to consider there and first thing I will say is that simply revving an engine for the sake of revving it, often isn't gonna give you any perceived advantages.
In order to actually make any power above your factory rev limit of 8000 RPM, first thing you're gonna need to make sure is that the intake system, the cylinder head and the exhaust can all actually work and flow above 8000 RPM. So this is also gonna come into conjunction with a cam profile that's going to be suited to air flow at that sort of RPM and of course then we get to a situation where the valve springs need to be suited to that particular cam profile in the RPM. So those are your key considerations there in terms of valve train. But of course the other aspect we do need to consider is the reliability of the rotating assembly of the engine itself. Going from 8000 to 10000 RPM is gonna put a huge amount more stress on your internal components.
One of the most highly stressed components in the engine is the big end bolts holding the cap of the connecting rod together and particularly as the piston goes past top dead centre on the exhaust stroke, it doesn't have any combustion pressure to help cushion and slow it as it comes up towards TDC because the exhaust valves are closing. So there's no pressure in the combustion chamber and the cap in the big end rod bolts have to do all of the work of slowing that piston down, reversing it and accelerating it away from TDC. So quite often if you're going from 8000 to 10000 RPM, you're gonna have to have a pretty serious rethink about the strength of your connecting rods in particular. And the last thing to consider with that as well, just in terms of that RPM increase, just remember that the forces involved here increase at the square of the RPM increase so it's actually much more significant than a lot of people would consider. Chad has asked, I brought up boost pressure reducing the effectiveness of the spring pressure, technically that's not entirely correct, engines don't understand pressure, they only know what's more molecules air in there, if there's 14 psi of boost behind the valve, then there should be 14 psi under the valve after the cylinder fills with air.
Then as soon as the piston goes up, the pressure increases, pushing the valves closed harder. Yep absolutely and exactly what I actually mentioned there. So you do need to take into account the pressure inside the combustion chamber. So if you look at the point however where the intake valves first start to open, we've got our boost pressure on one side of the valve, and at the beginning of our intake stroke, we're going to have relatively low pressure inside the combustion chamber. I don't think for one moment that let's say if we're running 35 psi of boost pressure and we've got 35 psi of seat pressure, that's not necessarily going to mean that that boost pressure's going to create valve float straight away.
There's a lot more going on in there and I did gloss over that but we do still need to take into account the boost pressure we're running when we are factoring in the valve springs that we are choosing there. So thanks for bringing that up, it is in itself a very complex topic. Robin has asked, is there a subsitute to assembly lube, actually seems hard to source in Denmark. Pretty surprising, this is a pretty generic product that is available from a range of manufacturers, I would've thought that most auto parts suppliers would be able to give you something like that. But absolutely, another option you can use is vaseline which you should be able to source pretty easily from any pharmacy.
Jono has asked, is it ever worth upgrading valve springs if not going past the factory rev limit? Kind of dealt with this already Jono, generally the answer would be no unless you are looking at increasing massive amounts of boost pressure there. Daniel has asked, actually the other thing I'll point out there, this comes back to our boost pressure and Jono's question there. In terms of our Subaru FA20, one of the reasons we have decided to increase, go to a valve spring that provides more seat pressure is not only that we are running boost pressure on this engine which was designed for naturally aspirated operation, we are also using an anti lag strategy. And that's important to mention here as well so I'll just deal with that. With an anti lag strategy, what we're doing is we are purposefully creating explosions in the exhaust manifold.
This creates large pressure spikes and these large pressure spikes can quite easily end up popping the valves back off their seats. And of course depending on when that happens in the engine cycle, that in itself can be fairly damaging. So by, if you are dealing with an engine that particularly is using anti lag for a rally application, often it is worthwhile upgrading at least your exhaust valve springs. Even if everything else basically should suit your application. Daniel has asked, does an asymmetrical lobe design reduce the need to have high seat pressures? Look these days the majority of performance cam profiles are actually asymmetrical to some degree or other so I can't speak to this too much detail because I don't design cams.
This really is a conversation for you cam manufacturer. It may have some impact but ultimately if you're going to go to a decent increase in cam profile, aggressiveness of your cam lift, duration et cetera, this will dictate almost certainly some change in your valve springs. Whether it allows you to get away with a slightly lighter valve spring pressure, I couldn't answer specifically. Alright guys that has brought us to the end of our questions there. So if you do have any further questions after this webinar has aired, please ask them in the forum, I'll be happy to answer them there.
Thanks for joining us and I look forward to seeing everyone next week.