Summary

Engine failures are an unfortunate part of motorsport, however before we simply rebuild the engine and have the same failure occur again, it’s critical to analyse the reason for the failure. In this webinar we’ll be analysing one of our own engine failures to get to the bottom of the cause.

00:00 Hey team, Andre from High Performance Academy, welcome along to another webinar.
00:03 This time we're going to be having a look at common engine failure modes and how to analyse what has resulted in a failure.
00:11 And this is something that is so often overlooked.
00:14 One of the common reasons that we would end up rebuilding an engine is because it's suffered some kind of failure.
00:21 This could be a mechanical failure, it could be tuning related, a parts failure, debris or foreign material related.
00:28 Regardless of what's caused that failure, it's very tempting to just pull the engine apart, replace the parts that are damaged or broken and put it all back together and fit it back to the car.
00:40 The problem is that 9 times out of 10 if we just approach the rebuild in this way, we're very likely to have not actually addressed the root cause of what failed in the first place and in that instance it's very likely that we're going to repeat the exact same failure and this is very frustrating, very expensive and wastes a huge amount of time.
01:01 So what we're going to do in this lesson is try and dive into some of the more common failures, analyse a bit deeper what's actually gone wrong, look at some of the signs that we should be looking for and then hopefully from that you can learn from our experiences as well as the experiences of others we've been involved with and should hopefully save you a bunch of money in the long run.
01:22 As usual we will have questions and answers at the end so if there's anything that I talk about that you would like me to go into more detail on or anything generally related to this specific topic of engine failures, please put those into the chat and we'll get to those at the end.
01:38 Alright so it's first of all really important to mention that there are almost an endless range of potential failure modes or things that can go wrong with our engines and clearly I'm not going to be able to do justice to every single one of those here in a 30-45 minute long webinar.
01:56 I'm just going to colour some of the key ones that I see repeatedly but this clearly is not an exhaustive list.
02:03 It's also worth mentioning that it can be really tricky to diagnose an engine failure sometimes, particularly one that's been relatively catastrophic or something that's happened at very high RPM.
02:17 That being that sometimes the root cause of the failure tends to get masked in the carnage that ensues.
02:25 If you have a connecting rod or a valve break at 9000 RPM, it's going to do a huge amount of damage and by the time we pull the engine apart it's very difficult often to actually figure out what did come first.
02:38 There are still some clues that we can look for though and we'll talk about those.
02:42 So the key here, the way I sort of tend to try and approach this is by sort of taking a step back and going through things in a more methodical fashion rather than trying to jump to conclusions based on the evidence that we are seeing.
02:56 We want to analyse that evidence step by step and see what we can specifically learn from it.
03:02 So what we're going to do is start with a failure that we saw on our Honda CRX K20 not long after we purchased it.
03:13 So a little back story on the car, not that it's too important for this particular webinar but we purchased this as a going concern.
03:20 It had a very healthy Honda K20, we aren't too sure how much mileage it actually had on it.
03:27 Some but not a lot, it was being used for endurance racing.
03:31 This thing was making around about 194 kW at the front wheels.
03:36 For a 2.0 litre naturally aspirated engine, certainly pretty healthy but not sort of ridiculous.
03:42 In order to do this, the key things that had been changed was to the pistons and connecting rods, aftermarket rods, aftermarket pistons from Wiseco with more compression.
03:52 The head had also been CNC ported, fitted with oversized valves from Supertech I think it was and matching valve springs and Brian Crower cams.
04:03 So for a middle of the road naturally aspirated K20 build, nothing particularly unusual there.
04:10 We'd competed in a few races with this car and had some pretty good success.
04:15 I was racing it in a three hour race at one of our local tracks and I was about an hour 40 into my stint just about ready to actually hand over to Ben.
04:25 We were in the lead by about a lap and a half so I had been cruising, basically rolling out the throttle at the end of straights and generally trying to short shift and give the engine a real easy time and save a bit of fuel in the midst.
04:39 That actually kind of ended up backfiring because I ended up with a misfire.
04:45 And that's all it felt like from the driver's seat, it felt like it had sort of either broken a plug or a coil had come unplugged or something like that.
04:54 No smoke, no sort of obvious signs of carnage pulled into the pits to see if we could get that sorted.
05:00 So we did a quick look in the engine bay and it was pretty clear at that point from the way the engine was running and also the amount of blow by coming out of the catch can that things were a little bit more serious.
05:12 When we pulled the engine apart, that was us done for the day but when we pulled the engine apart, we jump across to my laptop screen and this is what faced us.
05:20 So we can see here we've got two broken valves that have sort of been turned around and forced back into their valve seats.
05:29 This one here I think was completely missing and obviously the entire combustion chamber in the head has been destroyed by the ensuing damage which is sort of what I was talking about before, things bouncing around for a prolonged period of time, particularly in this case I drove the car back from the racetrack because we thought it was just an ignition misfire so yeah it doesn't really end that well.
05:54 I've got a couple of the parts here.
05:57 This is slightly different but very very similar sort of result that we see.
06:02 So this is the top of a K series piston and you can see where the valve has been bouncing around and this is the head of one of the exhaust valves that actually broke off.
06:15 And I think this was sort of sitting on the top of the piston.
06:18 Alright so how do we start analysing what's caused this? When we've got a failure related to a broken valve like this, probably the most common result of that, cause of that failure would be where we do not have sufficient valve to piston clearance.
06:39 And in this case what we'll do is see the valves contacting the crown of the piston and if they're doing this often enough and hard enough, what we'll end up doing is bending the valves and over time this can result in the head of the valve actually breaking off.
06:55 This is going to be borne out by seeing witness marks on our piston.
07:02 Now this is not a result of this, this is another failure that we're going to get into in a moment but what we can see here is these little witness marks at the back of the valve cut out, and we've got them here as well.
07:17 That shiny witness mark, that's indicative that the valve's been contacting the piston and particularly with a piston that's seen a reasonable amount of use, it's going to have a dark sort of carbon covering on the crown of the piston so these should be really really clear to see.
07:33 But when we're pulling an engine apart, actually irrespective of whether it's had a failure, if it's a modified engine, particularly one with an aggressive cam or cams, I would always be having a quick look at the crown of the piston just to ensure that we don't have any witness marks showing that we've had contact.
07:50 Now clearly this is something that we absolutely should be on top of when the engine is being built, we always recommend when you're going to an aggressive cam profile to always clay the top of the piston, we use Play-Doh and actually physically time the engine and make sure that you have got sufficient clearance.
08:11 But of course not always does that actually happen.
08:15 So the problem in this case was actually pretty apparent pretty quickly when we started stripping the engine and if we jump across to my laptop screen here, what we can see is that we've got this particular cylinder here, we've got no retainer sitting on the top of the valve spring and the valve spring's just floating.
08:35 Now granted the head did break off the valve but what we actually found is that the reason for this failure, the whole failure is that we suffered a valve spring failure.
08:46 And we can actually see the fatigue failure on the surface of the valve spring there.
08:53 I would say that this is very rare, in the 20 plus years that I've been involved in tuning and building cars, building engines, I have never seen a valve spring failure like this but that is what happened there.
09:08 These were a quality item, they're a Beehive valve spring that is sold through Calford Cams here in New Zealand but it's actually produced by Pac in the USA who's one of the premier manufacturers of valve springs.
09:22 This was a bit of a tricky situation, it's very very difficult, probably close to impossible to go back to a manufacturer with a race engine, the part like this and put your hand out and say hey this failed, it destroyed my engine and expect them to do almost anything.
09:39 Not saying it's impossible, hey it's definitely worth asking the question but my advice would be don't get your hopes up.
09:46 A real shame because this probably cost us somewhere in the region of $15,000 to rectify, given that the cylinder head alone, to replace that, find a good casting, have it modified, supply and fit the larger valves, the valve guides, everything that goes along with this, the CNC porting, that was around about a $6000 to $7000 operation, not to mention obviously it's destroyed the bottom end as well.
10:17 So a slightly unusual failure but generally with valve failures, it's going to normally come down to a valve to piston contact or a valve to valve contact which as I mentioned, is clearance or possibly our cam timing.
10:36 The next one that I would say this is probably, I didn't actually start with the most common but this next one is probably what I'd consider to be one of the most common failures that I've seen over my time and that is a bearing failure or what we'd often here refer to as a run bearing.
10:57 So let's have a look at a bearing shell under our overhead camera.
11:02 Can't sure remember what this one is for but this is kind of what you would expect to see from the surface finish of a new or used bearing that's in really good condition.
11:13 Granted there are a variety of different surface finishes and coatings that we now see on bearings, particularly race bearings so sometimes these could actually have a sort of a dark charcoal finish to them.
11:25 So let's have a look at this in perspective, this is a surface coating.
11:28 The important part with a bearing that most people who are new to engine building don't necessarily realise is that we should never be having metal to metal contact between the bearing shell and the journal of the crankshaft.
11:42 The bearing shell and the surface of the crankshaft should always be separated by a film of oil so we're never getting metal to metal contact and if we do, it's going to destroy that bearing incredibly quickly.
11:55 So when that happens, and I don't have a really good example but I've got a couple that are sort of on their way here.
12:01 So we'll get these ones under the overhead.
12:03 So we start getting this coppery colour and some scratching and in really bad examples it's going to basically tear the bearing shell completely apart and often we'll end up with a failure where we've got metal to metal contact, the bearing's worn away very quickly and all of this happens in a matter of a few seconds at high load and high RPM and then we get metal to metal contact which creates a lot of heat due to the friction and quite often what will happen is that the connecting rod, the big end of the connecting rod, let's just take that as an example, obviously this can happen with the main bearings as well, this will actually weld itself due to the heat to the crankshaft journal.
12:44 So it'll be solid and when that happens, obviously it can't rotate, the crankshaft crankover is still rotating so the next thing that happens is we snap the conrod in half and it punches what's left of it out through the block as it rotates around on the big end journal of the crankshaft.
13:01 So and again that's actually not what has happened with this, we'll get to this failure in a minute but that's quite common.
13:10 So when we have this sort of failure, there's a few things that are going to show up as an indication.
13:18 One thing, because I've experienced this more times than I care to think about while tuning cars on the dyno, is we're going to get a situation where one run after another, we start to mysteriously lose power for no obvious reason.
13:31 We might also find that when the engine, when we put the clutch in and the engine comes back to idle at the end of a run, it idles low or wants to stall and maybe it doesn't want to start anymore.
13:42 So those are all red flags that indicate something's wrong and you need to stop and assess what's going on there.
13:50 Now granted could be a range of other options or problems that are causing that but that's always a red flag for me.
13:57 I found this back in the days when we were tuning and building a lot of the Mitsubishi Evo 4G63s from the Evo 4 variant.
14:09 These, I won't go too deep into the weeds with it, these are an engine that were really problematic, they were known for an issue called crank walk.
14:17 The 1G DSMs had this issue as well.
14:21 And what this crank walk is is essentially when you put your foot on the clutch, you're putting a force into the end of the crankshaft, that crankshaft has to be supported in the engine block so that it doesn't try coming out the front of the block and this is done with a thrust bearing.
14:34 And this just restricts the longitudinal or end float movement in the crankshaft and the block.
14:42 With these particular engines though, there was a couple of issues that resulted in failures of the thrust bearing and what this would mean is that when you put your foot on the clutch, instead of the bearing supporting the crankshaft on this thin film of oil, it was pushing the crankshaft thrust face into the thrust bearing, wearing through the thrust bearing and when it got really bad, you would actually end up wearing the crankshaft into the block itself, simultaneously destroying the crankshaft and the block.
15:07 So not a lot of good things came out of this.
15:10 And this would sort of become apparent because when you put your foot on the clutch, the engine RPM would drop and the engine would want to stall.
15:18 So when we've got an issue like this, what we want to do is try and diagnose where this problem has come from.
15:27 Now normally with engines that don't have a known problem like the 4G63 crank walk, the most common reason for a bearing failure like this is two fold.
15:37 The first would be insufficient or excessive clearance during the assembly process.
15:44 So the clearance for our bearings needs to be quite specific, general rule of thumb is that we want about one thousandth of an inch clearance per inch of journal diameter.
15:54 Obviously if we've got a two inch journal, we want two thousandths of an inch.
15:58 That is only a starting point, we may want to adjust from there but that's a pretty typical sort of range we would expect to see.
16:06 So if we've got that clearance too tight, maybe instead of two thousandth we've got one thousandth of an inch, when the block and the engine are assembled, everything will still turn over but of course when we're under high load and high RPM, the crankshaft and the block are flexing and this results or can result in metal to metal contact and as I said it doesn't take much of this before we end up with a failure.
16:30 The other really common reason for bearing failures like this is as a result of a lack of lubrication.
16:38 This could be because we've run the engine out of oil but for our purposes, particularly if you're taking a street car out on a racetrack, the factory wet sump lubrication system is not generally built to stand the lateral and longitudinal G forces we'll see on a racetrack so this can result in the oil sloshing away from the oil pickup and when that happens, the oil pickup is going to gulp in a whole lot of air and it's going to pump that air through the bearings and then we can end up with metal to metal contact.
17:12 So that's the sort of two key elements that will result in a bearing failure like this.
17:18 There are others, I mean if you're running the wrong grade of oil, an oil that's really not fit for purpose like a low grade mineral oil on a race application could end up breaking down and also that breakdown does tend to occur if we're running excessive oil temperature, the oil viscosity tends to thin out as well.
17:37 So that's another common problem when we take a road car on the racetrack that doesn't have an oil cooler, the oil temperature can climb very quickly and if we don't have a way of monitoring this, this could happen without our knowledge.
17:49 Now one of the things when we are rebuilding an engine that has suffered from a bearing failure is that quite often a lot of the engine components are going to be a throwaway.
18:01 So for example as I mentioned, if we've got a connecting rod that has started to heat seize on the crankshaft, it's almost certainly going to destroy the crankshaft journal but also importantly, because of the amount of heat it's put into the crankshaft, it'll also almost certainly bend the crankshaft and we're going to end up removing material which is going to mean our journal size has been affected.
18:26 In the block as well, if we're talking about the main bearings, again if we've got a pickup like this and we're starting to see blueing or blackening on the bearing caps, this is going to be a really good indication that a lot of heat's gone into that and we can find that our main bearing tunnel is no longer true or no longer round.
18:44 So a lot of this could actually result in throwaways of our crankshaft, that's probably almost a given and quite often a throwaway of the block as well which is obviously pretty depressing.
18:56 Another really important tip though that I've got in relation to this, and this is something that so many people overlook, is with that bearing issue, we're going to be pumping a combination of bearing material and oil around the engine.
19:11 And this is going to get into the sump, it's going to go through the oil pump and importantly it's also going to end up going through the oil cooler if we've got one.
19:19 So if we've got an aftermarket oil cooler, quite often a lot of factory engines will use a water to oil heat exchanger, those will end up getting full, well not completely full but they will collect bearing material inside them and they're notoriously difficult, almost impossible to thoroughly clean out.
19:38 And what I've seen happen a couple of times in the past is people have rebuilt the engines, refitted the oil cooler, not thinking about this and then once they start the engine, it pumps the debris out of the oil cooler back into the engine and we simply end up with exactly the same problem happening again.
19:56 So generally I would highly recommend just simply replacing the oil cooler.
20:01 There are companies that quote that they can ultrasonically clean them, I am not quite so confident myself so I'd tread very carefully on that front.
20:13 Now another part, another aspect that does come into our bearing failures as well, I haven't got an example of this really.
20:21 We can see on this particular shell here, there are two light score marks.
20:26 Nothing specifically that I'd really be too worried about with this bearing because it's really already on its last legs anyway.
20:34 But if we're starting to see deep scoring on the bearing shell and a failure of the bearing shell starting as a result of this, this can be related to debris being trapped inside the engine and being pumped around the oiling system, just kind of like I talked about before but this could be as a result of maybe improper cleaning during engine assembly or some foreign material being introduced.
20:58 This would be something I'd definitely be looking at if I've had a failure very quickly after a fresh engine has been built.
21:07 Alright so that covers, as I say, what I'd probably consider is one of the most common failures I've seen in my time.
21:16 Really frustrating and definitely becomes a very expensive failure.
21:21 We'll go into a couple of failures that we've had in our unenviable journey with the Nissan SR20.
21:31 It's an engine that I'm really starting to build a significant dislike for but you get to learn from our pain.
21:39 Let's start with our very first engine which was a cast block, I think it was an S13 SR20 DET.
21:48 And in one of our early events we ended up with a very heavy vibration.
21:54 The engine was sort of losing power over a short period of time, the vibration was getting worse, culminating with a significant oil leak from the rear main.
22:06 That being said, it actually sounded quite clean and happy when we were revving it in the pits, there was no real obvious indication of the severity of the failure that we had going on.
22:19 And what that failure was, was our main bearing cap.
22:22 So we'll get this one under our overhead.
22:25 And you can see it's literally just cracked right through the centre of this cast cap.
22:31 Right through this little thread here which is an interesting addition that Nissan have provided which we can thread a bolt into and use that to actually pull the cap out of the engine block but in doing so has also weakened the cap.
22:45 Now first of all let's say that this is a known failure mode for these engines.
22:51 But not at the power levels that we were aiming for or expecting.
22:56 At this point the engine was somewhere around about 400, 450 wheel horsepower.
23:01 Generally it's accepted, everyone's going to have a different number here, that if you are aiming for 600, 650 plus horsepower, then you're definitely better off going to a billet cap because these are known to crack.
23:16 Same with the 2JZ although generally 800 to 900 wheel horsepower is about the range where those are known to crack.
23:22 So in this instance we did have a little bit of confusion about what had gone on here.
23:28 And this is one where we can't be conclusive because it's just impossible to know but just given the RPM range and the power level we were running, this shouldn't have happened.
23:39 However we believe that this also was a culmination of a problem with the gearbox that we were running at the time.
23:49 We were running a six speed sequential gearbox which was a hand me down from the old V8 that we were running and this gearbox, we chased this for two years before finally moving onto a Hollinger.
24:02 It had a very bad high speed vibration to the point where when the car was in sixth gear at 240, 250 kmh, you couldn't see out of any of the mirrors and kind of the fear of god became your breaking marker because the car felt like it was going to explode.
24:18 I genuinely can't explain how bad this vibration was.
24:23 Obviously not ideal and yes we were working pretty hard to try and resolve this.
24:28 We went through a couple of drive shafts, had them rebalanced a couple of times, went through different mounts, the gearbox went back to the manufacturer about half a dozen times, we tried a variety of different changes in the gearbox, some made it better but never fixed it.
24:43 At the same time we ended up seeing a range of failures to the engine as a result of this vibration.
24:50 Starting with our old V8, it had a sheet metal aluminium intake manifold, this started cracking sort of every second time we went to the track, it broke the mount for the alternator twice.
25:02 So that was before we had that particular engine fail for reasons I won't go into.
25:07 And we went to the SR20.
25:10 We also saw some vibration related problems on the SR20 and I think my pick is that is probably the most likely cause of this main bearing cap failure.
25:20 In hindsight, clearly if I had my time again we would have just started from the ground floor with a set of billet main caps.
25:27 But trying to get to the bottom of this was still important.
25:30 Let's just say we weren't at the power or RPM level where the factory cap should have been problematic.
25:38 Right so we'll get into a range of really really painful failures now which is connecting rod failures.
25:47 I've already talked about one such potential failure which is where the connecting rod big end bearing seizes on the crankshaft but there are also a range of other potential options.
25:57 Let's start with this little guy here.
26:00 This is a connecting rod from a factory Subaru FA20.
26:04 We at one time had a second Toyota 86 which had the factory FA20 engine but we had turbocharged it.
26:12 The engines actually are really quite amazingly stout.
26:16 Factually formed there, rated at 200 flywheel horsepower.
26:20 Can't actually quite remember what we usually see out of a naturally aspirated one on the dyno but suffice to say that on E85 with a BorgWarner EFR6758 turbo on 13 psi of boost, we were seeing about 390, 385 wheel horsepower.
26:38 So probably fair to say somewhere around about double what the stock power level was.
26:44 Despite that, all of the factory internals were stock, same factory pistons, same connecting rods.
26:51 Now we struck a problem and this was actually related to one of these, an HPA webinar on launch control and antilag.
27:01 And we were doing this on the FA20 and prior to the webinar, this was actually only about 15 minutes before we went live, I was just doing some testing which basically involved using launch control stationary at about 4000 RPM.
27:15 Now that launch control, for those who aren't aware, what it results in is a secondary rev limit, uses an ignition cut for that rev limit.
27:25 And what this means is that fuel and air are being passed through the cylinders where the ignition has been cut and they will burn and explode in the exhaust system.
27:34 This creates pressure spikes and it's pretty nasty on the engine in general.
27:39 And while doing this for about the fourth or fifth time, came back to idle and the engine was making a very subtle knocking noise.
27:46 I've got a pretty keen ear for any signs of mechanical damage, obviously this was not great.
27:53 Long story short, what we'd found is that this connecting rod, I don't actually think you're going to be able to see it, but basically the connecting rod had bent along its beam.
28:03 And when that happens, it obviously shortens up between the centre of the big end and the small end.
28:09 And the noise that I was hearing was the underside of the piston skirt just ever so slightly touching the underside of the bore.
28:17 So this is a case of a pressure spike resulting in, cylinder pressure basically resulting in an overstressing of the connecting rod and allowing it to actually buckle or bend along the rod length.
28:32 Very lucky to pick that up, obviously it had a mechanical noise that went along with it but if we hadn't picked that up, generally if you keep driving the car hard, because the connecting rod is now weakened and bent, it won't take too long before it then breaks and punches a hole out through the side of the block and at that point it's going to become much much more difficult to diagnose.
28:54 Now that was a very specific example but even with an aftermarket connecting rod, we can find that we can buckle these if we have excessive cylinder pressure.
29:04 Obviously if we're just asking too much from the particular conrod design, maybe we've got a conrod that's designed for, maybe call it 200 horsepower and we're trying to make 300, well that's not going to work.
29:17 On that note, the specification I just gave is quite often thrown around but also actually relatively useless for conrods.
29:24 The conrods don't care how much power we're making, the two metrics that they care about is cylinder pressure which is trying to force the connecting rod together so in a compressive manner, so that'll bend it under compression and the other one is RPM related where as the piston goes past top dead centre on the exhaust stroke, this time the exhaust valves are open so there's no cylinder compression to sort of cushion the piston, try and slow it down.
29:51 So it's the conrod's job as it goes over top dead centre to slow the mass of the piston down to stop it and then accelerate it away from top dead centre so that's trying to pull the connecting rod apart in tension.
30:02 Now there's two failure modes that we can see from this, one I'll show in a second.
30:05 That tensile failure is often going to actually show up with a broken connecting rod bolt.
30:11 This can be tricky to diagnose because again, that's going to end up in a really significant amount of carnage.
30:20 So that's our FA20 failure there, got off really lightly, an aftermarket set of rods and that engine did about two more years of racing, dyno work and to the best of my knowledge is still quite happily trundling around a racetrack with its new owner.
30:36 Now when we pulled that engine apart as well and found that, obviously it's really tempting to go and throw the kitchen sink at the engine in terms of all of the aftermarket parts.
30:45 And I see this happen time and time again.
30:49 Now yeah to a degree you're kind of future proofing for sure but in a lot of instances I see people needlessly spending money on parts that aren't necessary for their power or RPM levels and it's kind of just a waste of cash that really just didn't need to be spent.
31:07 So in that example, when we analysed the engine and looked at the connecting rods, those were obviously a known weak point, we need to replace those.
31:17 But in that instance the factory pistons were still in absolutely perfect condition.
31:22 I didn't really see any reason to replace those so we left those as is.
31:28 Now the next one that I'm going to talk about is another failure in our SR20 which only happened this year and I'm still suffering a bit of PTSD from it.
31:39 So let's jump across to my laptop screen.
31:42 And this is I think, at least for me a world record, we ended up losing number two connecting rod here and that put three holes through the block.
31:53 So we've got the two that we can see here, one up here, one down here and then there's a matching one at the bottom on the other side of the block.
32:01 So this actually happened while Ben was driving the car at the first round, or second round, first round of our endurance racing that obviously put us out for the rest of the season pretty much.
32:12 Really frustrating and this is actually quite an interesting case of all of the holes in the Swiss cheese kind of lining up in the perfect storm.
32:22 So let's have a look at some of the components out of this engine anyway.
32:26 And here for a start is the piston from number two cylinder.
32:30 It is not looking to be in very good condition.
32:35 This definitely is not going to do another turn.
32:38 You can see that it's heavily deformed in every shape, way and direction and it's been punched very very hard into the cylinder head, the side of the skirt's been broken out.
32:49 Interestingly the wrist pin actually still is nice and free in the pin boss.
32:56 OK so that's our piston, let's get that out of the way.
32:58 Let's get in the rest of our parts here.
33:00 For a variety of reasons I don't have all of them left but we can see our connecting rod big end and our connecting rod small end, I suspect that the rest that goes in the middle is somewhere on the side of a racetrack somewhere in New Zealand.
33:15 When we've got a failure like this, the first thing that I would be expecting is a bearing issue as I've already talked about.
33:25 This guy here basically heats these into the crankshaft, that'll immediately snap the rod and then the rest is essentially history.
33:33 But that's not what's happened here.
33:35 When I pulled the bottom end of the engine apart, the first thing we could see is that the connecting rod, there was no discolouration, none of that blueing or black which we would typically see over the back of the cap here.
33:47 That as you can see there is pristine, there's nothing wrong with it.
33:51 And even, it's a bit a little hard to see, I haven't got the bearings out of it, considering the carnage that ensued, the bearings actually look to be in remarkably good condition, the journal of the crankshaft also looked to be mint.
34:03 Obviously that's not our issue.
34:06 Then we go a bit deeper and we have a look at the small end of the rod.
34:10 And this is really all of the evidence that we need of what the failure mode here has been.
34:17 This has been peeled open and what we can see here, we've got a small forced oil, splash oiling hole in the underside of the wrist pin, small end of the rod I should say.
34:30 And while it's really hard to see on our overhead camera, we've actually got exactly the same.
34:34 So there's two of these little oiling holes, let's actually have a look at one that I haven't destroyed, this is what they should look like.
34:43 OK so what's happened is that the small end of the rod has basically failed through that hole because that's the weakest area and then it's been peeled open like a banana, the rod's been flailing around and obviously then it gets punched out through the side of the block, at the same time it's also punched the piston up into the cylinder head.
35:02 So this straight away to me now looks like an RPM related failure.
35:08 And as I've already discussed here, RPM becomes a problem because the rod basically has to reverse the direction of travel of the piston during that exhaust stroke.
35:20 On the compression stroke it's not so bad because the piston's coming up against closed valves, we've got fuel and air trapped in the cylinder and that acts as a bit of a cushion as the piston's coming up so the conrod's not really stressed in tension under those conditions, it's during the exhaust stroke.
35:37 So it is a RPM related failure and why has that been the case? This is where we do have to put our hand up and take some responsibility for this.
35:46 Car hadn't been used for about 2 years, it's undergone a pretty big birthday and overhaul and a big freshen up.
35:54 The last time we raced at this particular racetrack, this is the fastest racetrack in New Zealand, it's got an exceptionally long front straight and our car was pulling around 255, 260 kmh at the end of that straight.
36:08 That's significantly higher by a factor of maybe 20 to 25 kmh compared to the other tracks that we race at.
36:16 We had chosen gearing in the gearbox as well as a final drive ratio to suit that track.
36:21 And it did work.
36:23 However what we also found is that the tall final drive really kind of was a sacrifice for all of our other tracks to the point where our local racetrack, Highlands, we weren't using sixth gear and there's a couple of tight hairpins where we're so low in the RPM that we're basically outside of the useful range of the turbocharger.
36:43 Couple of years ago we entered a hill climb which is a standing start clearly and at the end of that hill climb we ended up breaking a tooth off the crown wheel in the diff.
36:52 This was a perfect time for us to go to a shorter final drive.
36:56 We did that and the intention, because we had a spare differential there, a spare diff, a Cusco LSD, was to build up a spare diff with a taller final drive to suit our long front straight racetrack.
37:07 However of course because the car wasn't raced for a period of two years, all of that information got forgotten and the first test session of the day, I went out on our minimum boost setting and was thinking to myself, why on earth am I almost touching the rev limiter on minimum boost? At which point after three laps I remembered and we're already at the race meeting, nothing we could do except for pump the rev limiter up.
37:33 Now obviously increasing a rev limit needs to be dealt with incredibly carefully and we need to know that the engine is going to be safe.
37:41 For endurance racing we normally rev this engine to about 8000 RPM.
37:45 However in its very first iteration, with some more aggressive aftermarket cams, I wanted to make peak power at about 8800 and we therefore revved it to 9000.
37:55 Now we had taken a couple of precautions to do so because we never really wanted to be at that sort of RPM but again if we come to our, over here, maybe it's this one here, no, yep this'll work.
38:10 So this is a stock off the shelf version of the K1 Technologies rod that we were running.
38:16 So same rod and the factory bolts that come in these rods or the stock bolts that come in the run of the mill ARP2000 3 8th of an inch bolt.
38:25 Nothing wrong with them, they're a good rod bolt but I was worried about their usefulness at very high RPM because of those tensile forces basically trying to rip the conrod apart.
38:36 So what we've actually gone to is ARP's custom aged 625 plus material.
38:42 Bit of a mouthful, basically it's a far superior material, much much stronger, also much much more expensive.
38:50 So I was relatively confident on the basis of that that these rods were going to be OK to 9000 RPM and they absolutely were.
38:58 What we actually found though was despite the engine running happily to 9000 RPM, it was impossible to keep cool for endurance racing at 9000 so we put in some stock P12 Primera cams, pulled the useful RPM range back and we tried to sort of rev it to 7800, 7900 RPM for endurance racing and we'd still rev it to 8200 or 8400 for our sprint races.
39:23 OK so we've already proven the engine was capable of 9000 RPM, what went wrong? Well I'm going to actually sort of bring in a second failure here.
39:32 And as part of this, when I freshened up the engine the last time, I've got a photo of it, I've got, I freshened up the last engine, this was two years ago now when we stopped racing it and the reason I did this was the last time I raced the car, when I went to put the car back on the trailer at the end of the day, when I started it up, I could hear that the compression wasn't quite even on cranking.
40:02 Now this is a really important skill for anyone in the performance automotive industry to kind of learn.
40:09 So when we crank the engine, in the time before it starts we can hear as the starter motor cranks the engine over, the different compression strokes.
40:17 And what I've sort of learned over my career is to sort of have a fairly finely tuned ear for when it does not sound even.
40:25 And the reason I want to take note of that is if the compressions aren't even on all cylinders, that can be indicative of a problem.
40:33 There's a variety of reasons for this, we might have a valve that's not seating properly, we might have damage to a piston, blow by or something like that.
40:42 But either way, any way it is, it's definitely not a good sign.
40:46 So when I heard that, this was the end of the season, the engine was being freshened up anyway, I sort of took it upon myself to figure out what was going on there and when we pulled the cylinder head off, this is a horrible photo but jump across to my laptop screen, this is what we saw on number four piston crown.
41:02 So this is cracking on the exhaust side valve pocket and this crack actually goes all the way through the crown of the piston.
41:11 So that's why I could hear it was down in compression.
41:13 I can imagine we were probably only a handful of laps away from this piston falling to pieces entirely.
41:20 The cracking also actually goes down through the side of the piston.
41:25 So it was pretty dramatic, it was very close to becoming a multi piece piston.
41:30 Why had that happened? So this was a CP piston, good quality brand.
41:36 What we can see is that that cracking, this is now looking at the underside of the piston crown, that cracking actually began or started at the radius on the underside of the pin boss on the bottom of the crown.
41:49 It just so happened that on number four piston, that crack had propagated all the way through to the crown.
41:54 The same cracking was visible on cylinders two and three, number one for some reason was untouched.
42:00 Now a great point here is that nobody knows everything and I've built up a lot of contacts in the tuning and engine building world over my time and what we'll typically do, this sort of range of people that I know will bounce ideas off each other or problems that we're seeing and often someone else will have seen the same things.
42:21 Rather than trying to reinvent the wheel and fix this all by ourself, I did this with someone who is really well versed with these CP pistons and they immediately said, oh yeah the factory off the shelf wrist pins are known to flex in your application and when they flex, they also flex the pin bosses in the piston and over time that results in the pin boss cracking.
42:46 So basically what we wanted to do or needed to do was move to a stronger wrist pin.
42:52 I don't have the original wrist pin here but as an example, let's just have a look in our overhead.
42:59 This is actually 4G63 so irrelevant but what we can see is the difference in the wall thickness of the pin here in the piston versus the new pins that we got for our CP pistons.
43:12 They're also not just thicker in the wall thickness, they are also made out of a different material, hence stronger, hence they're not going to flex.
43:22 Also, importantly for our problem here, they are heavier.
43:28 And that we believe was enough to push things over the edge and result in our wrist pin basically peeling the small end of the rod open and resulting in that failure.
43:39 Now obviously in hindsight we were right at the limit of those rods and this is a case that quite often happens, I'd call it scope creep.
43:50 We originally built this engine to support 500 horsepower.
43:53 And as we progressed and modified things and changed turbos and got the system dialled in, we ended up finding that for sprint or qualification formats, we were able to run it at about 630 wheel horsepower, maybe let's call that conservatively 650 flywheel.
44:13 And clearly that's nowhere near where we started out.
44:15 Now this isn't disrespectful to the K1 Technology rod, nothing wrong with it and if we were building a 400 to 500 horsepower road car engine, I'd still run one in an instant.
44:28 They're also much much lighter.
44:31 However in a freshen up or rebuild of our spare SR20 engine, we are now moving to a Nitto stroker kit.
44:41 So let's have a look at the Nitto rod, probably should have unpackaged this earlier.
44:47 I mean you don't have to be an engineer or a metallurgist to be able to see that there's physically a lot more material in the Nitto rod.
44:57 It is going to be significantly stronger and hence it's going to be more reliable at high RPM and high cylinder pressures.
45:06 Also you can see the amount of material around the small end bushing compared to the K1 rod.
45:14 So it's just really a case of making sure that the parts that you have chosen are actually going to be suited to the application.
45:23 Right let me just have a quick look back at my notes.
45:27 Couple, there's another failure that I wanted to go over here.
45:33 This is a piston that we've already seen a couple of times, we'll get this under our overhead.
45:36 I don't think I have the rest of that connecting rod but suffice to say it probably looks something a little bit like the SR21 anyway.
45:47 This was out of one of our 4G63 drag engines, was one of our customers' drag engines.
45:54 So this is a JE piston, flat top and you can see it's got these vertical gas ports through the top of the crown as well, little bit harder to see, these horizontal gas ports as well.
46:06 So this was from a methanol drag engine and it was making I think around about 900 wheel horsepower, running about 42, 45 psi of boost.
46:17 And this is the weirdest failure that I've ever had.
46:21 During a tuning session with this, I had an instantaneous failure of three connecting rods all at the same time, split second, all three let go instantaneously.
46:33 And this one was really hard to diagnose, we actually ended up having a subsequent failure at the track which is really what I came back to at the start of this, make sure that you diagnose and find out what this failure was caused by otherwise it's going to happen again.
46:47 This was a result of spark scatter as a result of a problem with the timing pickup or the trigger system that was fitted to the car.
46:56 So what was happening here is we were getting random spark events occurring nowhere near where they should have and this was resulting in stupid amounts of cylinder pressure which just exceeded the strength of the connecting rod and resulted in those instantaneous failures.
47:11 So pretty bizarre one, I've never seen anything like it since or anything like it from other people but strange failures can occur and they're always there to keep us on our toes.
47:23 We're getting towards the end of this so probably a good time to just mention if you've got questions, please get those in now and we'll go into those in a second.
47:32 Before we do that though, I also want to talk about tuning related failures.
47:38 Now these can come in a range of forms.
47:42 This one here is not strictly tuning related but we'll call it that for the purposes of our discussion.
47:50 This is a piston out of one of my own drag engines.
47:54 So this is out of my Evo that probably around the time this occurred we were there or thereabouts having the world record and that car went 8.2 at 180 mph.
48:06 Not this run though, definitely didn't do that on this run.
48:10 So this failure occurred in about the last 100 feet of the track and on face value, most people looking at this would probably say that this is a result of a lean out which to a degree it was.
48:22 Signs of this is the melting of the piston, the sort of sandblasted appearance, that's the word I'm looking for, sandblasted appearance on the crown which is normally indicative of detonation or knock occurring.
48:39 We've got severe scoring on the piston skirt showing that it's grown and attempted to seize in the bore and then we've obviously lanced out this hole in the side of the piston.
48:49 That's actually not necessarily the failure mode though.
48:54 In that particular engine we were running on methanol, this was about 50 psi of boost, running at about 11000 RPM and the way we were dealing with the fuel requirements because that requires a lot of fuel and we didn't have access to the injectors that are around today, I was running a set of Bosch 1600cc injectors which were referred to as Bosch in the blues.
49:19 This required three injectors per cylinder so we had one in the factory port location and then we had two on the back of the intake runner so the intake runner sort of curved up and we had two injectors coming into the back of that runner.
49:32 Now we were right at the limit of the fuel system here and what we sort of subsequently found out is that these particular injectors, if you run them past around about 85-90% injected duty cycle, their operation can become somewhat erratic and basically we ended up with this one cylinder leaning out as a result.
49:55 But it's not the lean issue that's caused this failure, this is actually a result of pre ignition and pre ignition is kind of like detonation on steroids.
50:08 It creates a huge amount of heat because the cylinder pressure is going to be building up from the time the piston is sort of coming up from bottom dead centre and it's trying to compress this fuel and air charge which has now been ignited way earlier than it should be so there's a huge amount of heat and pressure inside of the cylinder and pre ignition will sort of show up by, it's probably a little hard to see, the whole crown here has been melted and there's a big indent and also the way the whole side of the piston, including the rings has been melted, those are really really common indicators that pre ignition has been an issue.
50:45 So not strictly a tuning related issue but still it's sort of come down to this because we've had essentially an injector failure.
50:54 Expensive lesson to learn there but we did move to some superior injectors straight after that.
51:02 If you're wondering is there any indication that things are going wrong like this, with detonation we will see a failure occur relatively quickly but the failure as a result of detonation to a big degree is going to come down to the specific power levels basically how much power per cylinder the engine's making and the higher that power level, the quicker you're going to see a failure from detonation.
51:30 However with pre ignition, a failure like this is going to occur in maybe only a handful of engine cycles, it's very very destructive very very quickly so you don't get a chance to come back from this.
51:41 What we did see on the data is that the exhaust gas temperature on the cylinder sort of skyrocketed really rapidly.
51:48 This did bring on a driver warning but by the time the driver warning was on, the failure had already occurred, it'd be very difficult if not impossible to react quick enough to actually save the engine.
52:00 Now while that's an extreme situation, the other failure very similar to this is detonation, since I've just mentioned detonation I'll talk a little bit about that.
52:11 So that's an abnormal type of combustion.
52:13 This will generally be tuning related.
52:16 The ways we can create detonation would be threefold.
52:20 One would be to run too much boost, one would be to run too much ignition timing.
52:25 Third one would be to run a fuel with insufficient octane for the power that we're trying to make and quite commonly it can be two or three of those aspects all mixed in together.
52:39 So what this results in is pockets of unburned fuel and air around the outside of the combustion chamber spontaneously combusting.
52:46 And when this happens they essentially release all of their chemical energy very very quickly and this creates sharp pressure spikes inside the cylinder.
52:54 So it's almost like someone hitting down on the top of the piston with a sledgehammer.
52:58 Failures from this can be a piston failure.
53:02 So we can end up doing similar damage to this but generally not quite as extreme.
53:08 Quite often what will happen is that because it's just like someone slamming on the top of the piston with a hammer, we'll end up with the rings jammed in the ring grooves.
53:17 This has also actually occurred here.
53:20 And we also can end up bending or breaking a connecting rod because we've got a massive amount of compressive force that the conrod may not be capable of handling, particularly if it's a factory rod.
53:31 And then because all of that force is being transferred down through the connecting rod and into the bearing, we can also see bearing damage as a result of that as well.
53:41 So those are the sort of signs that indicate something's possibly up with our tune.
53:47 When we pull the engine apart as well, with an engine that has been suffering from detonation, we will see, again we'll go to our overhead camera, this like I say is extreme but we can sort of see that in the areas that the piston has failed, we've got this sort of grey sandblasted appearance.
54:06 And we'll generally see that around the extremities of the piston, it's actually generally around the intake valves, we'll actually see that on the outside of the piston crown.
54:17 So even if an engine hasn't suffered a failure, what I'm always looking for when I tear it down is the condition of the piston crown, I'm looking for that telltale sandblasted appearance that's going to tell me that I've got a problem with knock.
54:29 Also that'll quite often show, these are a feature, there's grooves on this top ring land here, this is a feature a lot of piston manufacturers are providing, often referred to as anti detonation grooves, I don't believe they do a damn thing for that.
54:43 But because we've got sort of sharp ridges here, these are very prone to beginning to melt when we're starting to get the first signs of detonation.
54:53 And likewise always want to make sure that my piston rings are free in the ring groove.
54:57 So if I try and spin the rings and they're sticky or stuck, that again is a red flag for me.
55:03 And that would indicate that we need to address our tune, maybe pull some boost or timing or both out of it or maybe move to a higher quality fuel.
55:13 Right I could go on for probably another hour but I think at this point we've covered some of the most common failures and hopefully that's given you a little bit of insight, hopefully you've learned from our PTSD.
55:27 And I'll just jump in and see if we do have any questions.
55:31 Yep.
55:36 First question, something I've been, I'm sorry I'm not quite sure how to pronounce the name so I won't even try and mess it up.
55:42 Something I've been thinking about for a long time, why is the wrist pin always such a simple shape, I imagine you could lose a lot of weight if you made the bore kind of convex if you get what I mean.
55:52 Yeah you're absolutely right and that actually often is done.
55:56 I don't have an example of that here.
55:59 But for a turbocharged engine where high cylinder pressures are the norm, generally the weight saving's not worth the potential reduction in strength but for a naturally aspirated engine, particularly one that's maybe seeing very high RPM and weight is more of an issue, then yeah what we generally see, go to our overhead here, is internally these would sort of be conical at each end where we don't need the strength and they'll have maximum thickness in the centre so yep that's actually a thing that can happen.
56:33 Diamond Stars asked, can you explain the pros and cons of I-beam versus H-beam? It's a great question.
56:40 I wish I could thoroughly but I have interviewed many many people who manufacture conrods and I have still not been able to get a conclusive answer to the two.
56:54 It almost comes down now when you're dealing with a quality conrod manufacturer like maybe Curilow Boostline, K1 for example, of personal preference or what that rod manufacturer is offering.
57:10 At the start when I was just getting into drag racing, the theory always was that the H-beam rod was stronger but I think these days the lines are getting blurred, I don't believe it's that cut and dried anymore.
57:26 So yeah maybe ask your conrod supplier what their recommendations are on that but like I say I've tried to do interviews at SEMA and PRI with the likes of Curilow and still not got a really conclusive answer on that.
57:42 Erics asked, will the sharp edge or point from the valve release at the edge of the piston crown cause hot spots and can this be controlled? Not specifically, what we do want to do is sort of try and avoid sharp edges where possible, let's just see what I can show here.
58:02 Yeah this one's probably a pretty good example.
58:06 So if we go to our overhead here, in hindsight here we've got a very very thin section here on the edge of this intake valve cutout.
58:17 We can see quite a bit thicker around the exhaust valve.
58:20 So obviously we're likely to see more heat generated around the exhaust side so in this case that thin area around the intake valve's probably not such an issue.
58:29 This is going to be tricky to show you but let's give it a go.
58:33 Looking carefully at our completely destroyed Wiseco K20 piston here, hopefully what we can see, and this isn't me modifying it or whoever built the engine modifying it, we've actually got a circular cutout here which would have been the edge of that pocket and likewise we've got the same here, this would be the intake valve considering that's bigger so that has been relieved there to make sure that we don't have a very thin bridge of material because that could end up becoming too hot and actually melting away.
59:07 Ultimately it's possible that that could end up being an ignition source that could start pre ignition as well.
59:15 So we want to try and stay away from sharp edges or thin sections of material on our pistons if we can be.
59:23 The other part of that question is will the piston squirters be enough to control it or will it need to be coated? Under piston oil squirters, I'm really torn on the topic of under piston oil squirters.
59:36 And the reason for this is that the theory is that the under piston oil squirters are going to spray oil underneath the piston crown and obviously the piston crown's the hottest part of the piston so that's going to help remove heat from the piston.
59:51 And I was sold on these with a 4A-GZE engine that I built many years ago, it was relatively stock, it had a set of rod bolts, ARP main studs, ARP head studs and a silver top 20 valve cylinder head and with a HKS GT30 turbo, we made 501 wheel horsepower in that engine on 32 psi of boost.
01:00:16 So the engine ran a very long and healthy life, never really had any issue with it other than the fact that the size of the big end bearings, they took a bit of a hammering and it needed a new set of bearings about once a year.
01:00:27 No big deal, very reliable engine, I was really happy with it.
01:00:31 And at the time I sort of put a lot of its success down using a factory semi forged piston.
01:00:38 I put a lot of the success down to the under piston oil squirters, keeping the pistons cool until I actually did a full freshen up of that engine and realised that I'd had my wires crossed on two engines that I was building at the same time and that engine didn't actually have under piston oil squirters at all.
01:00:55 That sort of had me questioning well are they really necessary and there's two schools of thought here.
01:01:01 One is the cooling benefits of the oil squirters and yeah that makes a lot of sense.
01:01:06 There's some downsides with this as well, it can overload the bores with oil which can end up resulting in oil being consumed and burned and obviously a smoky engine which no one wants.
01:01:20 The other problem is we are using some quantity of the oil which should really be predominantly there to lubricate the bearings to provide this oil spray to the underside of the piston crown.
01:01:34 So basically we don't have all of the oil serving the bearings and this can be problematic as well.
01:01:40 So a lot of people, engine builders, will actually purposely remove the under piston oil squirters and block them off to give more oil supply to the bearings.
01:01:48 Again I've run and built engines with and without oil squirters, I can't say I've ever noticed a conclusive or decisive advantage or disadvantage either way.
01:01:59 So personal preference is probably what I'd leave you with there, sorry I can't be more helpful.
01:02:05 Diamond Star Works has asked, is there a good way to determine between a loss of lubrication failure or a lack of clearance bearing failure? Yeah so there are a few signs.
01:02:14 First of all if we have a lubrication related failure, what we're probably going to find is that that will be more noticeable furthest away from where the oil is supplied to the crankshaft.
01:02:28 So if we're supplying oil, let's say from the front of the crankshaft and supplying it through, we might find that the rear main bearing or the, let's say it's a 4 cylinder, number 4 connecting rod bearing, that's looking really really ugly and as we move towards the front of the engine, it gets progressively better.
01:02:46 That would be a pretty good indication.
01:02:48 Another one would obviously be if we do have bearings that haven't quite picked up and aren't looking as ugly, we could go ahead and measure the clearance on those and just sort of see what's going on.
01:03:00 Also there's a bit of a knowledge base on engines that are popular for modification and you'll probably be able to find pretty easily if the engine that you've got, you're using it on a racetrack, if there's no issue with the oil supply.
01:03:13 Honda K20 would be a classic example, you'd never take one of those on a racetrack without adding a baffle kit to the sump as a minimum.
01:03:21 Marco has asked, what is your preferred piston to valve clearance to avoid a piston to valve contact failure? Yeah it sort of comes down a little bit to how brave you're feeling.
01:03:34 It also comes down to a big degree on how good of control you have over the valve chain.
01:03:41 Obviously if statically you've got, let's say 20 thou or half a mil clearance, that should be clearance irrespective.
01:03:48 But what we don't sort of take into account is that it's very easy to lose control of the valve chain at high RPM and that can easily take up half a mil of clearance.
01:03:59 I generally try and be a little bit more conservative and I wouldn't run anything less than about 40 or maybe even 60 thou clearance between the valve and the piston crown.
01:04:10 And that's going to be a situation where if you ask 10 different engine builders, they'll probably give you 10 different answers.
01:04:17 There's two clearances we need to look at with our valve to piston though.
01:04:20 One is the vertical clearance which is what I've been talking about so far but just as importantly is the radial clearance.
01:04:28 So let's get our overhead back on here.
01:04:30 So our valve is coming down, let's see how I can do this, our valve is coming down on an angle and obviously the valve pocket is cut out to suit that angle so the vertical clearance is exactly what we could expect, the clearance to the valve cut out.
01:04:45 The radial clearance though is the clearance out to the edge of this valve pocket.
01:04:49 And that's something that is quite easy to overlook, we need to make sure that we're maintaining again around about 60 thou of clearance radially as well.
01:05:00 Ghost6 has asked, can you use the spark plugs to help diagnose a detonation failure? Yeah absolutely, the spark plugs will also show signs of detonation, they're kind of like the canary in the mines, if you pull the plugs out, what we're looking for, in situations where we're just starting to run into detonation, you might see some balling of material, metal on the ceramic of the spark plug.
01:05:27 When you get a little bit more significant, you're going to start seeing the spark plug electrode, instead of having a nice sharp square edge, it's going to start rounding because it's starting to melt and in extreme situations you'll find you've probably blown the electrode clear off the spark plug.
01:05:43 At that point, another really useful tool for diagnosis is to use a bore scope which is a handheld little camera and it's got an extension, you can put it down the spark plug hole and basically have it poke around and look inside the cylinder.
01:05:59 With those bore scopes, these used to be really expensive, I think the one that we've got in the shop now is a couple of hundred bucks, it's kind of a no brainer if you're going to be doing this sort of stuff, can save you a lot of heartache and time.
01:06:12 With that bore scope, I would be looking again around the edges of the crown of the piston for those signs of the sandblasted appearance.
01:06:22 Barry G's asked, what are your views on high domed pistons, do you think the dome can shroud the flame front from travelling across the combustion chamber? Yeah 100% it absolutely can.
01:06:32 There is a fine line between trying to get compression into the cylinder but then having a dome that actually interferes with the flame front propagation.
01:06:40 It's a tough one because we don't generally get the opportunity to go and test six different designs of piston.
01:06:49 Like an OE or a race engine manufacturer could, back to back testing them to find out where that sweet spot between compression and flame front travel is.
01:06:58 But yeah definitely it can be a problem.
01:07:01 Suffice to say if you're dealing with off the shelf pistons from a name brand supplier like Wiseco, like this one is, they're probably not going to be supplying anything too outrageous, it's generally difficult to get enough compression into these engines like the K20 to be really problematic but yeah it is definitely something to be mindful of.
01:07:26 Alright that's got to the end of the questions so we will finish up there.
01:07:29 Remember if you are watching this at a later point in our webinar archive and you've got further questions on anything, please ask those in the forum and I'll be happy to answer them.
01:07:38 Thanks for watching and hopefully we can see you next time.