Blown 3.4 engine - what caused it?

hi all I blew my 3.4L engine on track back in the spring of 2022. I opened it yesterday with friends. 99K miles. It just let go after a long left hander. 295 tires in the rear, Advan A052. Big bang from below, cloud of smoke and oil, instant loss of power. I am trying to figure out how did this failure happen. I opened the engine and this is what I found (below). : IMS appears okay (it had an LN bearing in it put in approx 50K miles ago) No bore scoring Coolant tank empty. All coolant into the oil. Cylinder 1 (rear most on driver side) is where the issue was - cylinder wall broken almost completely - see pictures. Piston cocked inside. Rings broken. Connecting rod broken in 3 pieces. One piece still attached to the piston, second piece lodged into the crankshaft carrier (on passenger side), one pice missing. Not attached to crankshaft anymore. The crankshaft where conrod 1 used to be attached looks beat up, but not blue. A piece of piston got lodged between the cam sprocket and the timing chain on the passenger side, which made the timing all wrong on that side which resulted in all valves on passenger side getting in contact with pistons - so all bent. The intake on the driver side had lots of oil/coolant mixture. Less on passenger side. The 2 halves of the block had a weird crack on top which surprisingly looked old. No oil leaking. It is towards rear of engine so right on top of that cylinder 1, but still, looks old. The car sat since May 2022 when I blew the engine till yesterday. i appreciate any thoughts as to how this happened. The car has stock shocks, h&r springs (slightly shorter), rest is stock. Thanks pictures: https://photos.app.goo.gl/UA48cPiDYAJT1BV67

The #1 crank bearing seizes, rod snaps, piston drops below cyl wall and then the crank pushes it back up and shatters everything. Its the common failure in these motors when tracked. Here is mine.

OP - Complete bummer! The big question is: Are the case halves still good? Also begs the question if a UIDS would�ve prevented this catastrophic failure?

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D-Chunk?

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Mt educated guess, oil sloshed to the other side of the pan in your " long left hander " , starving the bearings of oil and the bearing with the most load at that exact time,, spun & seized up, looks like it was #1rod big end bearing. yes, an accusump or the UIDS probably would have prevented this failure.... jmo

What is the history of the engine? Oil used and intervals? Amount of track time? Did you put many miles on it personally or is it pretty much unknown? After every track day I do I�m always surprised I�m not making a post like yours. What did you do with the chassis?

In addition, what aos and sump where you running? How about how many times out on the track? Advanced, intermediate or novice speeds? What track?

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Wow, looks just like mine. We took off 2 more con rods from the crankshaft and there were no issues. I expected that oil starvation should have affected more than 1 piston. Why piston #1? Also - what did you do with the car? In response to other questions: - car was super maintained. Oil changed frequently. - in total perhaps 15 track days. - I put about $30K miles on the car over last 5 years or so. Very reliable prior to this issue. - the 2 halves are not usable. The broken con rod rotated and damaged the driver side. The crankshaft has a piece of conrod in it. Then - both halves have a crack in them on top of motor. I think the only usable stuff is cams, cam covers, accessories. - in regards to what I plan with the car - I am considering an LS3. Scared about oiling issues with that too (on track). Keep ideas going! What else could have happened to my engine?

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Stock AOS.. Stock sump. Motul 8100 Gen 2 changed 200 miles before. At upper level of normal (full). About 15 track days. However, the day I blew it - there was open track and tracked it quite a bit. Shenandoah at Summit Point - right before the back straight. I was at top of 4th when it let go. Did you see the 2 quarts or so of oil in the intake?

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So sorry to hear about this. AOS failure...hydrolock...carnage...?

There are two types of 996 owners: 1) Those who noticed that oil pressure drops on long sweeping corners, on the track or even the street at full operating temps. 2) Those that don�t notice it, because maybe they are looking at the place they should (the track). If the crank bearing failed, it�s probably due to lack of lubrication, which also causes excessive heat. UIDS and UAOS to prevent this from happening in the future. If you go an LS swap, you will want to address the oiling system there too.

Do you mean crank bearing seized or rod bearing seized? I think the rod bearing seized.

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Put a dry sump on the LS3. Can�t do that with an M96. It�s expensive but if you are serious about putting oil stability issues behind you - it�s the only way to do it and the LS has great dry sump options. As to what else� what�s the +1 rod bearing look like, looks like you de jeeper�d it.

Yes, LS3!!!

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@De Jeeper the most loaded question ever. Please provide a detailed response

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Two more quick questions. 1. How long were you out on the track in the session before it blew? 2. What does the water pump look like?

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Yes rod bearing, sorry. Not sure why its always the #1. My motor did have 200k miles in it but yea its heat and oil starvation. Also, the track version uaos helps keep the oil level at a good height, but I have no opinion on the uids pan as u have not seen adaquite data in the 996 platform to give an opinion and i real dont care because i wont fo back to a m96 platform for the track. Here is my rebuild thread....enjoy. https://rennlist.com/forums/996-foru...-the-dust.html

A L33 would be half the price of a LS3 ,, good cam + manifold 450 to 500 NA hp... LS engines need a accusump for road track use. (Except for the dry sump ones. OR if you want ot make a statement, run a 2014+ Gen5 4.3 V6 with boost.. Just cause I think it would be fun.. Light weight, 300HP almost stock, inside has all the cool parts... And with the 6 and the right exhaust it would still kinda sound right..

200 tread wear tires 100k mile engine Stock AOS Stock sump Race Track ;; extended session From the owners manual :::"The fitting of racing tires (e.g. slicks) for sporting events is not approved by Porsche. Very high cornering speeds can be achieved with racing tires. However, the resulting transverse acceleration values would jeopardize the adequate supply of oil to the engine. Porsche therefore will not accept any warranty or accept any liability for damage occurring as a result of non-compliance with this provision." Track work is a big boy event....you gotta pay to play...The modern 200 TW tires can reach the cornering G-forces of the 20+ year old racing slicks... What happens is the high cornering loads will shift the oil to the side of the oil sump and away from the pick-up tube...The pick-up tube will start to receive foam or oil/air at the surface of the oil level..This air will reach number 1 rod first and worst since it is the closest to receive the air...This will cause the temperature to spike and the clearance to open and jerk on the rod , breaking the rod and the rest is collateral damage... LS engines:: There are 40 different variations of LS engines. Half of them don't make more power than a stock 3.4 m96. Only three of them have forged cranks..LS7, LS9, and LSA None of then have Nitrided cranks.They are all induction hardened.. All will suffer from oiling issue on the track ( even the "Factory dry sump ones" ) All will have a higher CoG than a flat six...( it kills me when people tout corner ballance as proof of COG validation).. They sound like ****..low tech .. All Facts

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Even if this is true, who cares ? He mentioned LS3, an LS3 made 400HP from the factory. I think that is, like, a whole lot more than an M96. NOT a fact. The dry sumped LS3 motors came with forged cranks. And, so what ? 4 digit HP numbers on the stock cranks are common on boosted applications. https://help.summitracing.com/app/an...3-engine-specs The factory dry sump is a lot better than the wet sumps but I would generally agree with this statement as long as you are talking about stock oiling system parts. But, you can actually buy effective solutions that fix this problem from actual proven companies in the aftermarket that actually use engineers, data and testing to develop their products (not paying customers who think they are getting a fully tested product). As I said above, no such option exists with the M96 (maybe the system LN and Jake are developing will change this (it will likely cost a left nut). Again, who cares ? The car will be faster around the track (TON more HP), more reliable, have less expensive parts and not have to cost $25K plus to rebuild, but it could if you wanted it to. You throw this CoG thing around like its going to ruin the driving experience, I would love to hear what kabuki method you used to come up with that.

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Curious how you define the word "fact". M96, either a 3.4 or a 3.6 make what, 240-320whp max? and thats with a generous dyno. A 4.8 will lay down 300hp completely stock. Literally any LS variant will make more usable/reliable power than an M96. LS internals have been proven to handle 600-800hp easily for many years, forged crank or not. Any engine will suffer from oiling issues when pushed hard enough, i dont care what your autometer/factory dummy gauge reads, you'll starve the pick up at some point. I get it, you hate chevy engines. Ripping out one of these beautifully crafted m96 engines... that hold up so well over time... in place for a ls variant isnt for everyone. For a track car though, especially if you want something faster, its by far the best way to go.

A lot of great thoughts! A few details, answers and more questions: - I did not look inside the AOS - but it was still connected at both ends and no oil leak (as in the case with @De Jeeper ) - The water pump was new (maybe 1,000 miles on it) - but I did not take it off - somebody asked how it looked - I will take it off to see - I did find a connecting rod screw inside the engine (just like @De Jeeper again...) - it was bent and looked beat to death. - Connecting rod #1 was not connected to crankshaft any longer and the crankshaft looked beat in that area (same as @De Jeeper ) I continue to be surprised by the lack of any blueing where the #1 rod was connected to crankshaft. It seems that the main bearing (main bearings, not rod bearings) saw some heat but no blueing either. Is it possible that the rod just broke?? Or some sort of failure of one of the rod screws?? In regards to the car and its engine - I don't want this to turn into an M96 type of dispute. I knew it could happen. Also, I really like the chassis. I am underwhelmed about another M96 mainly because of the power, but also because to make one reliable for the track (LN sleeves, bored out, worked over heads, race AOS, IMS replaced, replacing all the chain/guides) will be $20K or so. Therefore, I'm thinking an LS3 because it has more power and because there is a company that sells a kit to adapt it (CPE). This will also be $20K+ but it has more power. It has to be an LS3 (or LS7 - but that is too expensive) because of the adapting harness that this company sells. This would be for the street. I am very aware of the LS3 oiling issues on track. It blows up like clockwork on track (it seems) due to oil starvation and oil getting stuck up in the heads. So - I am thinking to put in a crate LS3, return the car to daily driving duties. Now - if I like it (I don't know if I will because V8 in 911 chassis - how knows) and can't avoid taking it to track (I have a different track car now), then I will dry sump it with a kit from Aviaid, put a cam in it and widest tires I can fit. Any suggestions about what dry sump kit (I only know of Aviaid) are welcome. Thanks.

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Dailey Engineering

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Virtually any dry sump pump/kit manufacturer makes a set up for the LS engine. ARE, Peterson, Barnes, Auto Verdi...but the best is Dailey Engineering. You could even get used NASCAR stuff and make that work. Lots of options.

Although breaking a rod or connecting bolt is a lot more rare without seizing a bearing it still happens. Also it is possible as others have said these blocks can d-chunck and cause the piston to do catastrophic things. There is always the possibility of hyrolocking from an overwhelmed aos or a crack in the head dumping antifreezr? Vid from when mine let go. You Tube

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1bz, How long (approx minutes) were you on the track when the engine failed? Any idea if the water pump you replaced 1,000 miles ago had all its bits in place or if a few of the blades broke off?

Ibz, FWIW, I did a google search on Porsche 996 D-chunk and an oldie but goodie article from Total 911 popped up from 2006 written by Philip Raby tiled "Exploding Myths" who interviewed Autofarm and JZMachtech in the UK. I remember this article well because at this time we were all trying to identify the issues and mitigate them. As a side note, quite a bit of early mechanical information before 2007 came from these shops. "The Essential Companion" referenced their work quite a bit. This article came out after the RMS Go-No-Go panic and way before anybody had any idea that the water pump props could break off and lodge in the engine creating heat and cracking, as well as way before Bore Scoring became a top 3 term used in our vocabulary. Interestingly, at that time, the deep sump was not a mainstream solution nor was there an IMS Solution. Also at that time, folks started to migrate from the AOS to the Motorsports AOS realizing the oem AOS was about as durable as a Fiat. Take a look. You may find the article of interest. As a side note, it was theorized at the time that D-Chunking in the early 996.1s was caused by how the factory held the engines with a clamp thru the production process. The use of these clamps in production was eventually eliminated as the Factory recognized the issue. Don't know the accuracy of this theory, nor do we hear much about D-Chunking today. Why, I don't know. Maybe we are just fixated with the headlights, IMSB and Bore Scoring. But i will say this, we would have less engine failures on the track if folks would do the following... 1. Replace the WATER PUMP more often so the plastic bits dont get lodged in the engine creating heat and cracking. 2. Run a BETTER AOS to prevent intermix and hydralock, as well as handle more oil quantity and flow to improve oil pressure instability and mitigate oil starvation. 3. Run a BETTER SUMP that can increase the amount of oil in the system and mitigate oil pressure drops and oil starvation. 4. HEAT and COOLING is important. Don't track your 996 at speed on the track longer than 20-25 minutes unless you have a world class oil cooling system on the car. 5. Yep, make sure you have replaced your oem IMSB with a better one. Try this link. Other one wasn't working https://www.scribd.com/document/4950...otal911-July06

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Yes, all great advice. I was looking at deep sumps right before it blew. Also - at the time, I was migrating towards a different track car, so I didn't buy it before that last event. At any rate, with my experience now, I would be very leery about taking another M96 on track, even with motorsports aos, deep sump, and all. The pity is that I really, really love the car on track (and on the street). In regards to your previous question - I think I was out on track for 30-35 min when it blew.

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Except i had or did all of this and it still went kaboom. The m96 is a good engine, just not great for the track....even upgraded. My motor did have high miles and i knew it was gonna go eventually, so when it did, i was prepared and made lemonaid.

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Appreciate your thoughts. In contrast, I would in fact track my m96 powered 996.2 again on the track and plan too. After a 14 year stint on the track with all the stuff on the list I gave you, I never had any problems. But, I am not blind to the issues every engine may have and the preventative medicine that's needed. Don't care if it's an LS, K24, Mezger or M96. But we can't change the fact that nothing is perfect. I guess it's a mechanical reality. Whichever path you take on your engine, I wish you the best of luck. I would love to see a proliferation of engine swap threads that objectively discuss the pluses, minuses and things to be aware of, versus "the M96 is the worst engine and my _____ engine is the greatest thing since sliced bread." Please keep us posted on your progress! We all have an interest.

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You made some tasty lemonade. I hear you, doubt I would ever consider tracking a M96 or even Mezger powered car with 200k miles unless I was prepared to rebuild both. But no question, we can't change the fact that metal, plastic and rubber parts wear and then break. All we can do is mitigate the speed in which the parts may break. All engines will eventually need a rebuild.

I have a Raby 4.0 Stage II. I've run very long sessions, and back to back 40 minute sessions. At a recent Chin event, I ran the 30 minute orientation session, followed up by the 40 minute Red group, and followed it up with 40 minute Blue group session. On that Saturday, I drove the car for every possible track minute allowed (Orientation, all Red & Blue Sessions, and ended up with the 60 minute Happy Hour session) for almost 6 hours of track time. On Sunday, I ran every session again except the 60 minute Happy Hour so I could start the journey home. That weekend was around 11 hours of track time. A few weeks later I ran it hard for a PCA club race weekend and it answered the bell for each session. I do have an oil cooler and change the oil (XP9) between every track event. The Raby engine has been run about 5 track years (approximately 8 to 10 track events a year) and a bit more in a couple of those years. The car is now back at Raby's magical work shop for refresh/preventative work. The Raby engine has held up very well and I appreciate Raby and his team's work. Hopefully- it will hold up for another 5 years.

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But don't forget, they are plug and play!

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You really think so..?

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Yes, the Raby 4.0 set up for the track fixes many/all of the inherent m96 engine weak points, it is the crown jewel of the M96 builds no doubt... Curious, what was the total cost from start to finished installed engine...?

Alot of folks loose sight that you don't need to beat the heck out of the engine on the track to get speed from it. It's a momentum car. You just have to have the right set-up and inputs to balance it and keep the speed up. Certainly helps with engine life. Smoother is faster.

^Yeppers- The light weight combined with strong brakes/grippy tires/suspension allow late braking- and keeping the minimum speed as high as possible along with a stable rear allows speed to be squeezed out of the platform. Plenty of more powerful machines blow by me- but I have a lot of fun getting what I can out of it for what it is- rowing the gears and playing footsies with the pedals. Regarding total cost- I don't recall the exact amount but was in the 25-30K range. I am very happy with the difference in this and what a standard motor rebuild would have cost at that time. As everyone has stated many times- Raby builds a relationship with his clients. I continue to have regular conversations with Jud and him over these many years. It was a very worth while cost for me to enjoy track adventures.

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Absolutely. It lasted over 200k street miles, but like i said (and u cut off in the quote) its not great for the track.

I tracked my car once with all seasons, on the long left hand sweeper after a few laps the oil pressure would drop. Stopped tracking it as soon as I saw that. The engine isn't made for it.

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Agreed. Not in stock form it isnt. Nor is any M9X powered 986,987,996,997. But after you put in a better imsb, better aos, better sump you sure can. Problem is most folks just don't want to spend the money to properly set the car up for the track. Then they wonder why the engine blows. Same can be said for the LS, K24, etc. Gotta make sure its set up properly. Big difference between track driving and grocery getting as it pertains to oil pressure and stability requirements.

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the key difference is the cost to performance ratio. $10k invested into an ls2 for example gives you a freshly rebuilt motor with a better cam and valve springs ($5k), a dry sump ($4k), and a few other small upgrades. This motor would make 400rwhp all day long. I know nothing about the k24, but I imagine the same would be true, perhaps minus the hp number. To get a truly reliable track m96 (doing the work yourself), you're talking $5k for pistons/bores, ims solution at $1800, rods for $1500, head work ($1500 to $3k), bunch of replacement parts, all the gaskets, bolts etc that add up. I'd say even if you're not replacing absolutely everything, you're looking at about $15k. Then you add the UIDs at $3k and the uaos for another $300 and you're closing in on $20k real fast. And you end up with a motor that might put down 330rwhp on a good day. Another big one....just about any idiot can rebuild an lsx...if you need someone to build your M96....add a good $10k to $15k to the prices above. Yes, porsche has never been about performance for the money, but its double the money for like 100bhp less

No question, guys that can do the work themselves and like to tinker have a huge advantage to get what they want regardless of the engine route taken. Always comes down to end-game goals, preferences, money and time. With enough money and time, we can get what we want.

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Owning many Boxsters and 911 m96, I've thought this thru, like many here... The imsb solution along with other common sense parts (rms, clutch, throw out bearing, pilot shaft bearing, oil cooler, water pump, t-stat, uaos, belts, hoses, fittings, cables, etc) once the tranny is out, adds up to at least $5000+ if you do it all your self on your back. unless you're fortunate enough to have a stand under lift that most don't. $10,000 ??? if a shop does it all. (better be a good Porsche shop so they can get it all done correctly, as its not a Toyota, and needs specialized tools, knowledge, AND Porsche experti$e. Then start adding in expensive new sumps/pumps. Even then, how do you not wonder about the lousy defective lokisil 2 flaking off and bore scoring, or 5 sets of cam chains, pads, tensioners, actuators... Easy $15,000-20, including problematic cylinder scoring, with needed LN fix. My point, its easy to spend as much as the initial purchase price of the car on 'bulletproofing' the m96. Then start adding in the pretty stuff $$$... Could have just bought a Mezger Porsche 996 turbo or 996 gt for what the m96 + 'bulletproofing' with a lot less power will end up costing... A 15k TT on sale now for $52,000 on Bat. imo these 5 chain motors were a bad design from the get go, but to give Porsche benefit of the doubt it was their first attempt at a water cooled flat 6.... Whats bothersome is when Porsche realized how feeble/problematic the m96 was,, so then voided warranty if you installed great sticky tires in a Car brand that was always known for on a rail handling cars with the best tires... Don't get me wrong, I luv my 2 996 I have now, but know their pitfalls and can live with it. But both of them are mine because of sentimental value... jmho

I really liked the M96 in my 911. So much that for some time I also had a 986S. Then I got a 718 4 turbo and did not take a liking to that engine. Great power but I found the engine note lacking. I also did not like the throttle response. I can't really say the car has lag and it makes a ton of torque, but the throttle response (to me) was never on par with a boxer 6. I tend to agree with the cost analysis on making the M96 reliable for the track. I thought about selling the car and getting a 996TT, but I worry I will not like the throttle response. So, to me, the best option appears an LS3, which is the route I am taking. I purchased a crate LS3. I like the chassis too much to let it go. The question is - will I like it with the V8? Time will tell. If I do like it, I will look for a dry sump solution. If there are folks here with direct personal experience with an LS engine in a 996 - which dry sump did you use, and would you go with the same brand/model? I am new to LS engines and there's just so many options (which is great!) for dry sumps for this engine. Also - I do want to keep my AC.

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Yep. Unless the guy is a newbee and just doesnt know what he doesnt know, there isnt a guy at the track that isn't bitching about weak links and issues in all their cars. That includes mezgers. We all think the grass is greener on the other side of the street, then we walk over and see it isnt. But that's human nature. Without it, we wouldn't have any progress. But in spite of buying my 996.2 back in 2002, and putting much more than my original I urchase price into it with parts and service, I would do it all over again and again. Just too good of a car on the street and track to get caught up in the bitching and moaning. What I am happy about is the next wave of innovation that has been proliferating in the M96 world that is bringing new solutions to us. I am cheering on the engine swappers as well as the guys like Skip, Charles and Jake who are bringing out new solutions and more flexible solutions. Sure it all costs money, but as a 57 year old, there isn't much else I would rather spend my money on. Got too much stuff that sits in the house that I never use anyway. But the 996 is a different story.

If you go on Facebook Swapped Porsche, Tyler Chavis is on there and lots of LS conversion information on there.

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What you seemingly miss, so very often, is these weak links you speak of in regards to the 996 are excruciatingly expensive to repair AND there exists limited, not thoroughly vetted and also very expensive methods for mitigation. Couple that with the fix (a new built motor) that is way down on power compared to most of the modern machinery you are going to encounter on a track day. Not to mention if you do want to pony up the money for one of these underpowered very expensive built motors, the people who can build them for you are few and timelines likely to be long. I don�t hear a lot of people at the track complaining about items of the severity, minimal aftermarket support or cost to repair as the problems with the 996.

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Jason, love you man. Haven't missed a thing other than trying to figure out the point you are arguing this time. If it's that Porsche parts are expensive and Chevy parts are cheap, I gotta agree with you. So what do you want to talk about next?

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Sorry it went over your head.

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Did it? Or did it go over yours. I know it's got to be tough as a newbie. But after another 10 years, you will start to pick some things up. Love you like a younger brother.

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Indeed. I purchased Tyler's kit + a crate LS3. As to the M96 vs. LS3 - I absolutely love the M96. But after the experience with blowing it up - I am just not enthused about doing it again. It's tolerance for risk. Also - of note, my tolerance for risk in regards to the M96 changed AFTER I blew it up, so there's that. I also don't have @De Jeeper skill, so for me it was either sell the shell, or an LS3. Simple. And since I really like the chassis, there was no other choice. If I don't like the 996 with a V8 in it, I guess I could sell the car and not lose a lot of money since I plan on doing the swap myself (with a friend). That being said, the above reasoning applies to me. I can clearly see how other people choose to use the M96 on track, and I don't think that's wrong.

Blondes, brunettes or red heads. Comes down to your preference.

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You did, yes. if 10 more years of experience here dumbs my contribution down to fanboying and cheerleading - I prefer to stay a noob in perpetuity.