Unusual Case of Bore Scoring?

Some of you may have read my recent posts on the bent valves on 4-6 that I had which was caused by a green cam plug becoming jammed in the IMS sprocket and change on the pulley end of my engine. How this happened is beyond me as the last time I had the engine opened to work on the cams was 11 years ago and I certainly don't remember losing a cam plug inside the engine ( and I would have remembered it and gone back into the hea to retrieve it) and all six of the plugs were in place when I had the problem and dropped the engine. So as I said previously either it was a plug from 11 years ago or one that was in the engine from the time of manufacture that finally was caught up. This remains a mystery to me! So as I disassembled the engine I thought the problem was limited to the 4-6 head and the IMS and was planning on refreshing the engine and replacing the 4-6 head and the IMS. But yesterday I found bore scoring in what I think is an unusual location based on the Flat Six videos and the LN write-up. Mine is on the top of cylinder #3 as you can see from these photos. The liner for cylinder #3 The piston skirt from Cylinder #3 . All the other liners and pistons look good for an engine with 99,000 miles., So in all the writeup I have seen on bore scoring it is almost always on the 4-6 side usually in cylinder 5 or 6, and one the bottom of the liner. So is this really that unusual or what ight have caused it at this location? Perhaps a failure in the coating of the piston skirt? The challenge for me is that I really can't afford a full set of Nickies at this time. So do I replace this piston and put the engine back together and see how long I can get out of the engine? It was not making any noise, burning any oil or showing any soot on the exhaust. I have also found a set of cases and crank cradle that look to be good at a pretty good price, less than one third of a set of Nickies and Pistons, that I could purchased and put into the engine. I know this is not as good as the full deal from LN but the car is probably only worth $15,000 or so if it is running. And my goal is to get a few more years of use out of it. Or I could sell it as a roller and/or sell many of the parts. The transmission was rebuilt a couple of years ago by Gbox and should be worth a couple of gran alone. Looking for any comments.

Asymptomatic bore scoring.....starting to think this is more the case vs the exception. Best of luck with whatever direction you take. Sure your post will generate much discussion.

Wow - bummer! So, it looks like the scoring runs almost the complete stroke of the piston (top to bottom) so it's possible it started at the bottom (more common) and the lokasil/alusil grit material was dragged along to the top of the stroke... all conjecture at this point, so I guess it doesn't really matter. As more of these types of scenarios present themselves there may start to be more economical options to deal with them - as in maybe you can have just that cylinder re-coated... JR mentioned a process called Sumi-bore in a post yesterday that looks promising but maybe still in the testing phase (I have no idea what the availability is). In any case, good luck & keep us updated with your progress

Does the #3 wrist pin freely move in the connecting rod?

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yes there is no binding on the wrist pin

What oil do you use ?

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This. For as many cases are we see with very clear symptoms that have been discussed there is probably many more cases of scoring that is not showing any signs. Case in point is my friends C4S. Decently maintained, Mobil 1 oil changes with no consumption, no ticking or sooty tail pipes and has pretty advanced scoring. I posted a video of it before.

That's a real bummer Dharn55, I know your financial delima and wanting a frugal repair for only one cylinder.But the Locasil requires special tooling and knowledge to repair. Hartech is the only shop that I know of who has had enough experience in repairing/honing Locasil, and the only ones who has sourced an oversize piston that could be used to repair one cylinder, and be trusted, but shipping cost may make it cost prohibitive. And I['m not sure they even still do that process since they have gone to a full sleeve/Nickasil process. Sounds like your between "a rock and a hard place"...

Precisely why I asked my question.

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Precisely why I asked my question.

Wow! What a crazy problem. Conventional wisdom demands that you make it perfect before reassembling it. Unconventional wisdom would ask 2 questions: 'how long will the cylinder and new piston and rings last if you just clean and reassemble', and 'do you like disassembling and reassembling the engine'? Clearly you are comfortable taking the engine apart. If finances don't allow the 'right' fix, and the quick and dirty solution gets you down the road to a point where you will have the money to fix it 'right', and you don't mind taking things apart again when the time comes, why not?. Maybe there's more life there. But maybe it would result in other worse damage later on. Would knowing you are driving an injured engine around decrease your enjoyment of it or keep you keep you from driving it, even if you know the correct fix is coming? Sorry, too many questions. I'll stop now... Crazy talk. The correct answer is to fix it right. But I do have questions about the piston skirt coating. This failure is indicated in all bore scoring that I've looked through regardless of the cylinder. It's also inferred that gas quality and/or injector quality is also associated. Maybe injector 3 is leaking quite badly. Is there any way you can check it? If not, the issue may just be the original quality of the coating. Good luck finding the right solution. I hope you are able to keep the car, they are magnificent beasts.

i've heard of some places that are able to potentially do some re-plating or whatever. I'd have a chat with Hartech, which may be able to give you some options.

I'm not sure if this is it but a quick search found this - https://www.uschrome.com/nicom-nikas...ing-and-repair . May be worth a call to see if the cost would be more manageable for you.

Meanwhile, yesterday in another thread a guy who had his engine rebuilt by Hartech in 2017 posted an audio that clearly sounds like piston slap, and he says the sound has been like that since he got it back from the shop, though it never made that sound before the work was done.

Looks normal to me for Stage III bore scoring. Nothing new there. Just because bank two is the most common too have bore scoring, don't confuse that with the myth that it can't happen own bank one. People do that all the time. The issue can be one cylinder on bank two, or bank 1, 1 cylinder on each bank, or any other mixed up issue. It can also be all 6 cylinders scored, with some worse than others. Tis is why you start the bore scope inspections on bank two, because usually we can check only cylinder 6, and find enough to down the engine. If we don't find the issue on #6, we do all the rest of the cylinders till we find the issue. I can typically find the cylinder that the issue is on by looking at the exhaust flanges at the point t where they meet the cylinder head. If you cut corners trying to save money, and or prove a point, only one person will lose, and that's the one doing the work/ paying the bill. Plating original cylinders is not good because the parent material is weak, and the acid etching processes will break down the parent material even more. The next issue you'll have will start with coolant leaking out the tailpipe, and when it happens, you'll know that you have a cracked cylinder. Br frugal, and you'll get to spend money twice in most every case. I have seen blocks prepped by US Chrome that had every expansion plug eaten away by acid during the process. That can tell you how aggressive the processes are. My ticketing system is currently full of people who are redoing jobs after they chose the wrong guy, wrong process, or cut a corner when repairing things .Currently "re-do work" is now making up 1/3 of what we build, as we go behind the last shop and throw away what they did. In lots of cases that means throwing away a whole engine case, and flushing thousands down the toilet, all because some had k tried to cut a corner, or save money. It was a lot better before these engines were being molested by there wrong people holding a wrench. We are losing more and more virgins every day. Now I'll tell you what I tell everyone I talk to: if you are not in love with the car, don't bother fixing it. You are better top cut your losses now, and sell it as it is, rather than throwing money at some haphazard, half *** fix that doesn't work. You are going to lose money either way, but if you cut corners with a half *** fix, you also get to lose a lot more sleep over it, as well as wasting even more money. Pass it on to the next guy who will appreciate the fact that now he can make the engine the way that he wants it. We are doing groundbreaking SUMEbore development today with M9X, 9A1 and Aircooled Porsche engines. This is being done very early, so when the environmentalists kill the Nikisil process, we will have the market by the *****, with everything perfected. I expect SUMEbore to take two more years to fully develop, and the first of our engines that will see it offered to customers will be the 9A!/ DFI engines. It won't happen soon, and it will NOT be "cheaper" than Nikisil. SUMEbore is the newest cylinder technology available, and Porsche first used it with the 918 Spyder. You'll learn more about this in some videos soon, since the first SUMEbore M9X engine has logged 5K miles and has been inspected and reconfigured with a different ring package to gather more data. This is a joint collaboration between Flat 6, LN Engineering, Total Seal Piston Rings, and the Oak Ridge National Laboratories. The gloves are off! The first SUMEbore Aircooled engine is on my dyno today. I built it so I can have the cylinders removed in 20 minutes for data, and have the engine parts swapped and back together as soon as it cools down. The first session is an engine that is 1/2 SUMEbore, and 1/2 Nikisil.

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Just for curiosity... you have any statistics on how many cases the scoring is affected only on bank 1?

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I'm sure that will resonate well with the market / future potential customers.

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I say take the rough edges off the piston reinstall and see how many more miles you get out of it. Maybe even get another used piston and put it in there. These engines are all or nothing when it comes time to rebuild, and it�s a shame that they are not good. You essentially have a roller now, it will still be a roller when it really goes south. Document it and see how long it lasts, I would imagine lots of these engines look like that inside, but nobody knows.

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What does it feel like and can you estimate how deep it is? whats up with the cylinder next door, it looks like it has a liner?

PT3 , I think Hartech can do one cylinder and apply the strengthening rings to the other two cylinders to create a better case , probably source a piston for you aswel , last time I enquired , a single sleeve was about �800 , plus the rings and honing other two cylinders plus a piston I would guess around �1200 ish plus shipping , which is not too bad as this engine could go back together without need to tear down again after this , best I can think of, for this situation !

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Yea, but Dharn55 is on another Continent from Hartech, so the shipping cost may make it not the best/frugal choice..

Lovin’ the new avatar Doc!

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Thanks Joe, the new Avatar was sent to me by one of my best friends I've known for 60 years.. Signed: Dr. h. c. Porschetech3

We've all heard the noise in videos that have been posted and shared, some of us in our own videos when we post them during what Jake has described as a denial phase. Jake also demonstrated the "piston slap" in one of the videos in his series. I like to believe I have a reasonable understanding of the basics, but then I see or read something that raises questions - sometimes I get a more detailed understanding of something and other times I have to relearn what I thought I knew. I've learned a lot since I heard the noise in my own car, I'll tell you that. So with that in mind, perhaps someone could explain in simple terms: 1) I understand debris flaking and getting scraped along the cylinder wall. I can even picture it. I thought that the pistons weren't actually supposed to be in contact with the wall, generally, but then why the coating on the pistons? Is that just for those parts of the stroke that the angle of the connection rod will cause some contact? 2) the scoring doesn't change the shape of the cylinder, but gouges it. There are plenty of surfaces with ribs or scratches or channels along which another surface could still glide smoothly. If the cylinder was out of shape, I would understand the slap easier, but it seems odd it would do that with just lines scored in the surface - unless I'm underestimating how much material has been removed. And finally; 3) if the noise we hear is "THE" piston slapping against the cylinder, why does it sound the same when we have extensive scoring in 3 cylinders, not just one. Again, for the record I am not in denial - I'll have mine back with Hartech sleeves soon.

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These are classic points/ questions. Rennvision in conjunction with Flat Six Innovations, LN Engineering, and Total Seal Piston Rings is hosting a free bore scoring webinar on 1.21.2021 The panel will consist of: Jake Raby/ Flat 6 Innovations Charles Navarro/ LN Engineering Lake Speed Jr./ Total Seal Piston Rings Tony Callas/ Callas Rennsport Stand by next week for the details. We've been working on this content for weeks, and I think anyone wondering about bore scoring will learn a ton from it.

Thanks Jake