Engine Failure @ 14k miles

[Chrisyphus]

Originally Posted by former 240 s14

The brief that talks about the oil pump gears is not from Rogue. It's from the manufacturer of the gear kit. It's also an engineering brief, which talks about all the issues you bring up in your points.

Before we go back and forth first try reading it. My father, who was an aerospace engineer, appreciated the detail and write up. Not saying he is the end all be all, but he has more experience in engineer briefs than I have.

Rubin

It is important to clarify a couple of things about the benefits of the overdrive kit,

As discussed previously, Flow is more important than pressure, but pressure is still a critical safety driver, and it is generated when a sufficient flow meets a restriction.

There is a hypothesis developing that it is possible that, in the process of adding clearance to the rod bearings, because they are a known issue, the #1 crank bearing is the next weak link in the system. The reduction in overall pressure resulting from decreased restriction in the rod bearings causes materially less oil volume to pass through the front main, enough to cause catastrophic failure.

To be clear on what I am saying: fluid dynamics demands that pressure be the same at every bearing, assuming there is adequate flow to generate a reasonable minimum pressure, and that all oil passages to all bearings are of fairly similar restriction. If you lower the restriction in one, you will reduce the pressure in all, but the oil volume will be biased significantly towards the outlets (bearings) with less restriction (more clearance).

On the beans, while the engine is turning at a higher RPM, this is fine. The pump is likely still flowing more oil than the system needs. But when putting around town, this issue will be at its worst. This is why the original hypothesis, when these failures started, was the start/stop functionality.

[Chrisyphus]

Originally Posted by former 240 s14

Welp update, the replacement block was not good, cylinder wall damage that wouldn't smooth out during machining, but we have a lead on another one from the same place so, fingers crossed.

I do still want to run an accusump. The system in general makes alot of sense, I just need to figure out the whole kit first and which ones I need. I'll probably get the car up and running/driving first then focus on that.

Rubin

Do they still have it? We will buy it. We bore these blocks up to 94MM. It'll buff, and I need to start collecting parts for my 4.7

Edit, it seems like you have two bad cores? I imagine if the prices are reasonable, we will take both. I'll discuss with Peter on Monday, pending your response!

[Chrisyphus]

Sorry for blowing you up like this, Rubin. I have been ignoring the track section of this forum, and this thread floored me.

I really appreciate the approach you're taking to doing everything as well as possible so as not have this issue ever again. Kudos.

If there is anything we at Partee can do to help in the process, let us know, please.

[former 240 s14]

Originally Posted by Chrisyphus

Sorry for blowing you up like this, Rubin. I have been ignoring the track section of this forum, and this thread floored me.

I really appreciate the approach you're taking to doing everything as well as possible so as not have this issue ever again. Kudos.

If there is anything we at Partee can do to help in the process, let us know, please.

Hi Chris, a huge thank you for taking the time (which wasn't insignificant) to respond and review the thread. I'm a fan of M539 so I know your shop from his videos, and you are also near one of my favorite tracks I race, VIR.

Reach out to Ben about the cores, not sure if they've been picked up or not. Let me warn you though that my engine that had it's failure has a cracked main journal, not sure you can do anything with that paperweight. The gouge in the other blocks cylinder wall was massive, not sure 94MM will be enough to clean it up.

I have decided away from machining the main journal as you suggested, this has been a fluid situation as Ben (Rogue) and I learn more. Luckily Ben is a personal friend and we've been through alot (I unfortunately totaled his 40 race car) at Mid Ohio years ago but made sure I took care of him (and he took care of me.)

Moving forward the current plan is to have the new core (and a core Ben is building for inventory) is having a very reputable shop in NV sleeve the engines. I know it's not Partree's preference and I respect that. The group that's sleeving it used to build S65's for IMSA, SCCA, and the Grandam Series. They think for track usage the blocks without sleeves aren't the biggest fan of high temps. We are also overboring to 92.5MM to go with forged pistons, ACL oversized bearings, and the pump gears.

I do have one question for you, has your group worked with oil accumilator/accusumps yet? From my research not many BMW guys run these but they almost sound perfect for us that can't afford a dry sump. I was planning on calling Pegasus Auto Racing as they seem to be pretty familiar with these systems.

Thanks again and I appreciate the extra set of professional eyes on this build!

Rubin

[Chrisyphus]

Yeah the spin main block is scrap to us- it could be saved with some effort and a line home, but we choose not to do that in any situation. As more of this happens, it may become a more common thing.

I’m curious, if you’re sleeping the block, why does the gouge matter? Surely it’s not so deep that sleeves wouldn’t eliminate it?

Re our philosophy on sleeves vs. doing it the correct way ;p, it’s your engine and your call brother! There are absolutely a lot of companies who have had success doing it. Peter is more against sleeping than I am, but I am also the one who designed a 1000whp capable twin screw supercharger for the S65 behind his back: our opinion is that for N.A., a properly done Alusil refinishing is superior. But I personally will concede that a well done sleeved block, while sub optimal, is a solid option. I think a lot of the biases that race shops have supporting sleeved builds is that Alusil as a little more of an unknown as compared to something that works in so so so many racing applications. Why mess with the recipe that works for them? If that’s the shop you want to work with, and they are more comfortable with sleeving, then asking them to do Alusil reconditioning is a fools errand. I think you made a good choice there.

As far as accusumps are concerned, we as an organization have not- Peter is of the mindset that if something is worth doing, it is worth doing in the best possible way. As a result of this, we either sell daily dry dumps, or we use the OEM oiling system. One of our engine builders, on the other hand, has been building racing engines for ~ 30 years in every discipline of racing. He has done a lot of builds with accusumps, and says that as long as expectations are realistic and that the plumbing/design is done well , they can be a great solution.

The big thing that you have to accept is that an accusump is a stop gap for oil starvation, not a solution. Your oil pump will likely be consuming a liter or more per second at 7000 RPM (that is not an exact number, I do not know the actual flow rate of the pump off the top of my head) and so if you have a 3 liter accusump, that can empty in as little as three seconds.

Add to that, if the pickup is in fact injecting air under high lateral acceleration, it causes more issue than simple loss of pressure. It also causes aeration of the oil, which disrupts the wedge, dramatically decreasing hydraulic protection.

It’s definitely a worthy insurance policy, especially if the issue isn’t the pickup sucking air, and is instead a lack of fluid flow in certain situations.


There are so so so many moving parts on this topic, so many variables, so much complexity. It could be as simple as the pickup not being sufficiently submerged, or it could be something else entirely.


I have my hypothesis, but it’s half baked at this point and will require significant research to determine if it is correct or not.

[former 240 s14]

Originally Posted by Chrisyphus

I’m curious, if you’re sleeping the block, why does the gouge matter? Surely it’s not so deep that sleeves wouldn’t eliminate it?

We just made the pivot to sleeving. The gouge is pretty substantial and near the top of the cylinder wall. Seating the sleeve may have some small issue (but alas, I am not an expert, lol!)

Originally Posted by Chrisyphus

Re our philosophy on sleeves vs. doing it the correct way ;p, it’s your engine and your call brother! There are absolutely a lot of companies who have had success doing it. Peter is more against sleeping than I am, but I am also the one who designed a 1000whp capable twin screw supercharger for the S65 behind his back: our opinion is that for N.A., a properly done Alusil refinishing is superior. But I personally will concede that a well done sleeved block, while sub optimal, is a solid option. I think a lot of the biases that race shops have supporting sleeved builds is that Alusil as a little more of an unknown as compared to something that works in so so so many racing applications. Why mess with the recipe that works for them? If that’s the shop you want to work with, and they are more comfortable with sleeving, then asking them to do Alusil reconditioning is a fools errand. I think you made a good choice there.

You are more an expert than I, and trust me I respect that than most! What I have heard is that under long duration high stress sessions the block cylinder wall can go egg shapped, i.e. the block is not strong enough for that type of scenario. That's why most of the IMSA and SCCA engine builds sleeved their blocks.

Originally Posted by Chrisyphus

As far as accusumps are concerned, we as an organization have not- Peter is of the mindset that if something is worth doing, it is worth doing in the best possible way. As a result of this, we either sell daily dry dumps, or we use the OEM oiling system. One of our engine builders, on the other hand, has been building racing engines for ~ 30 years in every discipline of racing. He has done a lot of builds with accusumps, and says that as long as expectations are realistic and that the plumbing/design is done well , they can be a great solution.

The big thing that you have to accept is that an accusump is a stop gap for oil starvation, not a solution. Your oil pump will likely be consuming a liter or more per second at 7000 RPM (that is not an exact number, I do not know the actual flow rate of the pump off the top of my head) and so if you have a 3 liter accusump, that can empty in as little as three seconds.

From my understanding of an oil accumilator the back air pressure of the accumilator dictates the speed the oil flows. The more air you put in the accumilator it takes space away from oil storage but increases the speed of which it dispurses. If you lower the air pressure on the back side you can fill more oil but the speed of which it flows is lower. Below is a great video from Moroso on their accumilator. Worth a watch when you are on the toilet, lol.

Really enjoy chatting with you. I am going to send you a PM with my contact info. I love learning from people and I appreciate your knowledge and enthusiasm.

Rubin

[Chrisyphus]

Originally Posted by former 240 s14

We just made the pivot to sleeving. The gouge is pretty substantial and near the top of the cylinder wall. Seating the sleeve may have some small issue (but alas, I am not an expert, lol!)

Oh wow, yeah, yikes! That thing must have taken a beating. I wonder what happened to it lol

Originally Posted by former 240 s14

You are more an expert than I, and trust me I respect that than most! What I have heard is that under long duration high stress sessions the block cylinder wall can go egg shapped, i.e. the block is not strong enough for that type of scenario. That's why most of the IMSA and SCCA engine builds sleeved their blocks.

I really appreciate it! I am just lucky enough to do this as a day job; it allows me the luxury of researching, obsessing, and still affording blueberries for my girls lol. Because I am so blessed, I feel I have an obligation to the community to do the best engineering and design I am capable of, and share that information as effectively as I can. To be clear, though, it is not all me- the team I am surrounded by is incredible. Depending on the topic, I feel like the least intelligent person in the room- I learn something from the people around me every day. It is truly a privilege to be a part of this organisation.

When it comes to sleeves vs. Alusil reconditioning, every shop has an opinion. Ours is based on decades of experience. Our original machinist, Dale Spooner (now retired, but still comes in weekly), has been doing engine machine work since the 80s, and is the machinist behind every single Subaru motor built by Vermont Sports Car (Subaru Rally Team America) up until 2021/2, when he educated their new machinist on best practices and helped to design the Billet blocks they are using now. VSC is the team behind David Higgins and Travis Pastrana's Subaru rally cars, among others. Dale does not like the idea of sleeving an Alusil block unless it is structurally necessary (read: BOOST), and expects regular rebuilds as preventive maintenance. He educated me that Alusil blocks, if done correctly, will stand up to NA racing abuse without issue, and that, due to the extreme hardness of the Silicon crystals the piston rings interact with, it will wear more slowly than an iron sleeve, while being a lower-friction surface for the piston rings. All while being far, far more reliable over a decade or more and over 100k miles.

This is further supported by Peter's original engine-building partner, Dusty Renteria. Dusty owned the engine-building shop that Dinan bought and rebranded as their own. Dusty was Dinan's Motorsports director. He designed and built Dinan's most successful engines- until Dinan sold out to private equity and had his secretary hand Dusty (and all other expensive, key leadership in the organisation) a termination notice. Dusty and Peter had been friends for a while at this point, so, armed with his lack of an NDA and employment, Dusty joined Peter and started building engines, armed with YEARS of building Dinan's racing engines. Dusty hasn't worked directly with us for several years, but to add to his credentials, he is a team manager in IMSA, and his team won the 2025 IMSA GTD PRO Michelin Endurance Cup Championship. He agreed with Dale's assessment of Alusil, as it was the same conclusion he and Dinan (as a result) had come to well over a decade prior.

And finally, our own internal experience. If we wanted to, we could sleeve every block we do. It would be much faster and cheaper, and we could still charge the same price, since our price point is already competitive with shops that sleeve their blocks. Both of our machinists and our 2nd engine builder have extensive experience sleeving blocks. If it were the better way of doing things, we would do it without question. But, after hundreds of engines out the door with a 0% return rate due to build failure, while having heard so many horror stories from clients who went to other builders, got a sleeved block, and then had issue after issue... We are quite confident that we are doing it right.


Point being, while Partee Racing is a relatively new name, we as an organisation have an extensive pedigree in motorsports. Still, if you told that story to one of these other shops (who very likely also have an extensive pedigree of their own) that say Alusil is too weak or soft for track abuse, they will say we do not know what we're talking about and that they know better. It is okay to be wrong.

The Daytona Prototype S62 we, and Dinan before us, build, for example, is an Alusil block with no sleeves. That is about as extreme an NA BMW engine as I have ever seen. A 5.0 S62 spinning at just under 8000 RPM, making 600 horsepower, for 24 hours without issue, winning races and championships.

Alusil isnt the issue- Improper Alusil surface conditioning is. The same can typically be said of sleeved blocks. Improper sleeving is the issue, not necessarily the practice of sleeving.

As I said above, every shop has an opinion on the topic. In my experience, if you look past the spin each shop is giving, their opinion aligns almost directly with whatever their capabilities are. Every shop I know of that has mastered Alusil reconditioning says that sleeving is inferior and should only be used for boosted applications.

Every shop without experience conditioning Alusil cylinder walls says it's better to sleeve the block, yeah, they can do it, but it's just not as good as sleeving for reason X.

Alusil conditioning is not a very technically complex procedure. You can look up the process and specs on Goodson's website. Actually doing it accurately and consistently requires specialised and expensive tooling and equipment.

https://goodson.com/blogs/goodson-ga...-engine-blocks

Sure, you can do it by applying the gobbagoop to the felt hones after roughing in the bores with a diamond hone and let it rip for the specified amount of time, but at what pressure specifically? What speed? What reciprocation ratio?

Every time someone tells me they did it themselves or had the "really good shop in town" do it for them, I ask for details, and the best answer I get back is " I asked the machinist and they said they did it at the standard rate for XXX amount of time" then when I ask how they confirmed the surface to be correct, its usually "they said it looked right, dull matte, like the goodson website says"... brother, we do this every day. When we check our work, we very rarely nail the surface finish on the first attempt. Everything matters. Temperature, humidity, your mood, the current inclination of mercury, the price of tea in China... every little variable matters when we're talking about specified sizes that are 1/1000th of the thickness of a human hair. And I am expected to believe that any race shop can get it right? No. lol. It is not as simple as it looks, and if someone thinks it is, it is because they do not know what they do not know.

One of my NCOs told me, back when I was Private First Class Knerr, "confidence is the feeling you had before you fully understood the situation." The above is one such example.

Unlike most others, we have mastered both methodologies. We can do both methods. We have done both for BMW clients. We refuse to do it if we disagree that it is the optimal application of a sleeved block.


Well... that ended up being more in-depth than I intended lol. I do not mean to change your mind or anything along those lines; I only want to share information, our experiences, and explain how we came to our stance on an exceedingly polarising topic. As I said earlier, you have a shop that you know and trust, they believe in and have a ton of experience with sleeving these blocks, which makes your decision the right decision for you, and without question, that is what matters most.

Originally Posted by former 240 s14

From my understanding of an oil accumilator the back air pressure of the accumilator dictates the speed the oil flows. The more air you put in the accumilator it takes space away from oil storage but increases the speed of which it dispurses. If you lower the air pressure on the back side you can fill more oil but the speed of which it flows is lower. Below is a great video from Moroso on their accumilator. Worth a watch when you are on the toilet, lol.

Yeah, so maybe I could have elaborated a little more. Your statement is accurate, but the Moroso video leaves out some nuance.

It is not as simple as the precharge dictating the oil flow speed. ΔPressure is. the Δ between the precharge chamber pressure and the oil pressure in the galley will determine how fast the oil flows in or out, and the air mass, (not the air volume) of the precharge will determine how much oil is allowed into the accumulator, based on the fact that it will naturally find an equillibrium of the mass of the compressible fluid (air) and the pressure of the uncompressible fluid (oil). This equilibrium is dynamic, as oil pressure will change based on the engine's operating conditions and whether the pump is being starved of oil.

This dynamically changing equilibrium is what we are leveraging to prevent bearing wear due to the oil pump picking up air. For example:

-If/when air is ingested (without an accusump), oil pressure goes from ~70 to 30 (or less), and now your engine might be blown, or at the very least, it's life has shortened.

If/when air is ingested (with an accusump, the oil pressure is at 70, your precharge pressure is 20 PSI, and at 70 PSI, you have 3 litres of oil), if the flow from your pump is now only enough to support 40 PSI, the accumulator will prevent the system pressure from immediately falling to 40 psi. Instead, pressure drop will be a function of the needed flow to maintain a given pressure in the lubrication system, and the ratio at which the air pressure drops per litre of oil (this is determined by the ratio of air volume to oil volume in the accumulator chambers at the highest equilibrium pressure; the more air there is relative to the oil, the slower the air pressure will drop), until oil the oil pressure reaches a new equilibrium with the air at 40 PSI. is your precharge was 20 PSI, you will not use all of the oil in the system, even if the pump only flows enough volume to generate 40 PSI indefinitely.

If your oil pressure drops to zero- a severe starvation situation, then yes, it would empty the accumulator and the flow rate at which that would happen would be driven by precharge pressure over the restriction in the lubrication system. This is because if the pump's output is not enough to generate any pressure, the ΔP would simply be the measured pressure. If in this situation, you needed 0.75 litres per second of oil volume flow to maintain 70 PSI of oil pressure and appropriate cooling, the accumulator would start flowing 0.75L as soon as the pump's pressure fails. At this rate, you have 4 seconds until it is emptied, but halfway there, the pressure in the system, and the flow as a result, will be down to 45ish PSI, and the flow will be down commensurately. So the entire event will take longer than 4 seconds, but the pressure drop and flow drops will be such that you have roughly 3 seconds until the system has stopped protecting you.. better than nothing, but RIP.

The good news is that in all but the worst cases, this will protect you. But you need to set up the kit properly and be aware of its limitations. It is not going to supply rock-solid oil pressure all the time, no matter what, as a dry sump would, but in all but the worst-case scenarios, it will provide some serious peace of mind.

Additionally, if the real culprit driving these oil starvation issues (not that this is what's happened here) is what I think it is, an Accusump could be the ideal solution.

Originally Posted by former 240 s14

Really enjoy chatting with you. I am going to send you a PM with my contact info. I love learning from people and I appreciate your knowledge and enthusiasm.

Rubin

Thanks for the kind words! As I said above, it is a privilege.

[F4rmost]

Man, there is so much good information in this thread. Thanks for taking the time to write everything.

Rubin, please post how you install the accusump! It may very well be something I include in the future just for piece of mind/that extra little bit of protection.

Great read about the Alusil reconditioning as well. I feel lucky to have Partee somewhat close by, granted I hope to never have to use you guys out of necessity, but rather out of a want (because that would mean I had an engine failure).

[omgzirra_exe]

I love reading Chris’s posts, honestly.

And it’s nice being able to confirm some of this from my own experience too, considering I put 80k miles on a non-sleeved 4.4L stroker.

One thing I always tell people about built motors, sleeved or not, is that they still require preventative rebuilds or at least inspections based on race hours or mileage. And people look at me like I’m crazy when I say that.

Getting 80k out of mine was a blessing. It was as basic as a rebuild could be: a used, bare block I bought back in 2019 and built up.

I can support non-sleeved builds and I can support sleeved builds. Both have their place. But I’ve never been able to put into words why I don’t think sleeves are necessary for our engines unless you’re going forced induction or your cylinder walls are too far gone to salvage.

[Chrisyphus]

Originally Posted by F4rmost

Man, there is so much good information in this thread. Thanks for taking the time to write everything.

Rubin, please post how you install the accusump! It may very well be something I include in the future just for piece of mind/that extra little bit of protection.

Great read about the Alusil reconditioning as well. I feel lucky to have Partee somewhat close by, granted I hope to never have to use you guys out of necessity, but rather out of a want (because that would mean I had an engine failure).

Use us for a plenum or a BBK lol

Kidding, but hopefully you can make it out to one of our meets/open houses this year!

[Chrisyphus]

Originally Posted by omgzirra_exe

I love reading Chris’s posts, honestly.

And it’s nice being able to confirm some of this from my own experience too, considering I put 80k miles on a non-sleeved 4.4L stroker.

One thing I always tell people about built motors, sleeved or not, is that they still require preventative rebuilds or at least inspections based on race hours or mileage. And people look at me like I’m crazy when I say that.

Getting 80k out of mine was a blessing. It was as basic as a rebuild could be: a used, bare block I bought back in 2019 and built up.

I can support non-sleeved builds and I can support sleeved builds. Both have their place. But I’ve never been able to put into words why I don’t think sleeves are necessary for our engines unless you’re going forced induction or your cylinder walls are too far gone to salvage.

Thanks, brother!

Couldn't agree more, and it is probably 40% of our customers who need to be educated on the expectations of a built motor. It doesn't mean it will last longer under normal conditions; it means it will survive far worse conditions and make more power doing it, but it is not going to be a 200k-mile engine with zero maintenance. This is racecar shit lol.

[former 240 s14]

Great news! The engine has arrived to Rogue for assembly. The block and sleeves look gorgeous from what I can see. Forged CP Pistons 12.5:1, OEM Rods, and custom matched ACL (Race and Standard) bearings for mains and rods, and SRD oil pump gears. Once the short block is assembled there Ben will ship it here for us to put the heads and accessories on. More pics to come but I couldn't wait to share the news.

Rubin

[former 240 s14]

Build in progress at Rogue. More pics to come.

[DrFerry]

Originally Posted by former 240 s14

Build in progress at Rogue. More pics to come.

Good luck with the build. I saw some marks / crud on one of the crank journals. Whatever it is should probably be cleaned off.... See photo screen shot with comments below.
.

[Brandoch]

Originally Posted by DrFerry

Good luck with the build. I saw some marks / crud on one of the crank journals. Whatever it is should probably be cleaned off.... See photo screen shot with comments below.
.

That's not a journal, that's part of the long snout.

[DrFerry]

Originally Posted by Brandoch

That's not a journal, that's part of the long snout.

Oh, okay. Thanks.

[Brandoch]

Originally Posted by DrFerry

Oh, okay. Thanks.

This is what I believe is a large factor in #1 main bearing failure. After #1 main you have 2 double row timing chains (BMW usually only does single row chains), then the oil pump gear, then that portion that you pointed out, then the harmonic balancer, then the crank pulley driving 2 belts.
That is a long distance without being supported with the load of the timing system and the ancillary systems.

[DrFerry]

Originally Posted by Brandoch

This is what I believe is a large factor in #1 main bearing failure. After #1 main you have 2 double row timing chains (BMW usually only does single row chains), then the oil pump gear, then that portion that you pointed out, then the harmonic balancer, then the crank pulley driving 2 belts. That is a long distance without being supported with the load of the timing system and the ancillary systems.

Very good points and I'll add on top of all of those challenges that IMO the main bearing shells are narrow and somewhat small in terms of bearing surface area - especially for an engine capable of such high RPM and high compression. Then there's the start/stop theory mentioned above where the chain tensioners hold the timing chains in tension for about 2 mins before residual oil pressure bleeds down possible causing #1 main bearing wear in start/stop situations shorter than about 2 minutes.
.

[Chrisyphus]

Originally Posted by Brandoch

This is what I believe is a large factor in #1 main bearing failure. After #1 main you have 2 double row timing chains (BMW usually only does single row chains), then the oil pump gear, then that portion that you pointed out, then the harmonic balancer, then the crank pulley driving 2 belts.
That is a long distance without being supported with the load of the timing system and the ancillary systems.

Originally Posted by DrFerry

Very good points and I'll add on top of all of those challenges that IMO the main bearing shells are narrow and somewhat small in terms of bearing surface area - especially for an engine capable of such high RPM and high compression. Then there's the start/stop theory mentioned above where the chain tensioners hold the timing chains in tension for about 2 mins before residual oil pressure bleeds down possible causing #1 main bearing wear in start/stop situations shorter than about 2 minutes.
.

Since it is relevant to this discussion, please read pages 3-6 of SRD's paper.

Many people believe the timing chains are the issue. They're not. The serpentine belts are not. None of that is what is causing front main wear.

The load transferred to the main bearings from combustion events exceeds 4,000 pounds per event.

As correctly stated in the SRD paper, hydrodynamic lubrication is the principal in which journal bearings use to support immense loads. Their paper is specifically referring to rod bearings, but it is also true for main bearings- it would take SIGNIFICANTLY more than 25,000 PSI to overcome the lubricity of the oil in the main bearings. No part of the accessory drive is coming close to pulling on the crank that hard, regardless of leverage.

Hell, Coyotes have dual timing chains as well (double roller or single roller, the tensioner is going to put the same pulling force on the crank), and an equally long snout on the front of the crank, and when aggressively supercharged with the belt drive all the way at the end of the snout, they're as likely to break the snout off the crank as they are to damage the front main bearing.

I can see how the start/stop is more believable, but that, too, is not the root issue. Millions of cars on the road have start/stop. None blows up as often as the S65... to include the Yote.

It all boils down to two things: insufficient oil flow overall, and far too tight of clearances overall, but especially in the #1 main because the #1 main bearing grows by ~ .0004" when the harmonic balancer bolts are torqued to spec, and unlike the S62, BMW did not build in any addtional clearance from the factory to account for this.

If the bearing is too tight for hydrodynamic lubrication to occur, AND there are intermittent oil-pressure losses at speed, AND you exacerbate the issue by running wider rod-bearing clearances... you're going to have a bad time.

[DrFerry]

Sorry for the repeat post. Just in case some haven't seen this yet.
.

.

[former 240 s14]

Originally Posted by Chrisyphus

It all boils down to two things: insufficient oil flow overall, and far too tight of clearances overall, but especially in the #1 main because the #1 main bearing grows by ~ .0004" when the harmonic balancer bolts are torqued to spec, and unlike the S62, BMW did not build in any addtional clearance from the factory to account for this.

This is the gold right here. I was going to ask why the main bearing 1 was always failing, thank you for the logical explanation.

Rubin

[My Schnell]

Originally Posted by DrFerry

Sorry for the repeat post. Just in case some haven't seen this yet.
.
https://www.youtube.com/watch?v=EufAV2UIIAM
.

I went through this but skipped ahead … did they say anything about these blocks? Were they running boost, significant track time, what oils were they running, mileage, how they’re driven day-to-day, or anything about how they were used?

Just curious if there is more to those blocks’ stories than daily driven #1 bearing failures.