Bore scoring: 3.8 997.1 and early 3.4 Caymans more common says Hartech

Saw this in the current issue of 911 and Porsche World (UK publication) and figured I'd share. image-3628404268.jpg

I read recently that because the IMS bearing is a relatively "easy" fix (compared to bore scoring) it is the reason so many companies have come out with their own IMS fix. Bore scoring, as stated in the article, is really the bigger, more widespread issue. There is no easy, inexpensive fix for bore scoring - so, no adverts in the Porsche mags to replace your cylinders.

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^Really?^... Can you say "Nickies" (cylinder sleeves)...I see 'em all the time.

Well, you do see ads for Nickies, but how many others compared to the number of IMS retrofits? The price difference is what I was actually referring to. Bore scoring is an expensive repair...

You heard it from the other expert on the other side of the pond. Yup, a lot more suckers in the U.S. I guess...

"Of the 25 engines Hartech typically has going through the process, about 20 are in for bore scoring problems. What's more, most of those are 3.8L 997.1 engines with early 3.4L Cayman engines the next most common." - I'm feeling pretty good about my 3.6L right about now.

Apparently, Hartech reads the Good Week thread - note the "dreaded" bore scoring.

From Hartech re. 3.4L & 3.6l engines -ovality+cracking. "The 3.4 and 3.6 996 engine has a piston 3mm bigger than the 3.2 S but the outer casting mould is the same size – so the cylinder wall thickness of this more powerful engine is measurably thinner than the preceeding engine sizes – resulting in a similar scenario to the result of boring a conventional engine out bigger –too thin !" http://www.hartech.org/docs/buyers%2...20part%204.pdf Note that "support rings" may preserve the weaker bores -see Hartech for details. Specifically about bore scoring: http://www.hartech.org/docs/buyers%2...20part%205.pdf The page layout of the first link is awful but the content useful/interesting/depressing in terms of engine longevity & costs For the impatient reader,the issues are: The coolant flow to each cylinder is reduced (so a greater temperature difference across the cylinders top to bottom). The thermostat is fitted to the inlet – increasing engine running temperatures compared to traditional engines with the same thermostat setting but on the outlet. The radiators are a long way from the engine slowing reaction times to sudden temperature increases. The radiators are partially blocked by the air conditioning condensers and often with leaves and can corrode and then leak. The temperature gauge reads lower than the actual temperature. The piston spray jets are in the bottom of the cylinders (favouring bank 1) unable to lubricate the thrust face of bank 2 as well as on bank 1. The coolant enters under the cylinders (favouring bank 1) The cylinders gradually go oval in the thrust direction increasing blow by and piston temperatures. The coolant outlet is lower than the highest point of the crankcase potentially trapping bubbles allowing temperatures at the cylinder walls to rise The head gasket controls the balance of coolant to each cylinder and the cylinder heads. Oil and coolant change intervals have been increased reducing oil condition and effectiveness As a result the cylinder walls run hotter than traditional engines and as the mileage increases the cylinder ovality increases and so does the cylinderwall temperature and oil viscosity drops.

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Hence the reason why they offer closed deck services as well. But with that said, Jake does offer the 3.8L boring option from the 3.6L block so it can't be all that bad or a big issue.

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Bingo, the fear mongering marketing(as well as the outright lies and deceit) have indeed made suckers out of many...a lot of money made off of people replacing pefectly good IM$ bearings.

The best remedy is Knowledge. I am grateful to Hartech for the education. It would be interesting to read counterpoints from any source that is better qualified.Is there such a source?

As the 997 is getting older more issues will come up to the surface, the 996 has been disected to the bone, we already know what's going on, but what amaze me is how the 997 keep solid price wise.

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IMO seems a lot of garage queens suffer from IMS vs daily drivers. Then again daily drivers get scored cylinders more often in colder climate areas when the winter garage queens don't. The IMS is a great way to fear monger though even though most of us who have done it ended up having perfectly good ones with no signs of any play or wear. Easy thing to reproduce and fix. Isn't there someone here running some $100 ebay bearing in his 996 with no issues.

The Hartech research shows the reasons for scoring are not just cold starts. Sadly there are no easy remedies according to Hartech. The simpler Hartech suggestions are better oil(Miller Nano or Castrol Magnatech 10-40),new coolant and lower temp thermostat.U.K. has a very mild climate compared to most of the USA so their oil recommendations requires a summer/winter modification(??) for us.

Hi Read the article with interest but I feel that there is an important descrepency in it that call into question the numbers and commonality of the issue. Halfway down column 2 the statement says how common bore distortion is in older 996's. However, in the earlier paragraph it states that of the average 25 engines in the shops at Hartech 20 of those 25 are 3.8L 997.1's and not 996's?? It cannot be both ways. Maybe the trade for IMS is dropping off for a number of reasons - those that were going to fail have done so, the concerned have changed theirs and a new pending disaster is needed! There always seems to be a 'concern' for Porsche owners that enjoy their cars and want to keep them well, for want of a better word, to encourage the opening of wallets!! Regards GW

No dependencies. They're saying bore scoring is more common for 997 engines and bore distortion and cracking are more common for 996 engines. Scoring and distortion are two different things. What surprise me most in the article are the prices of the repair: - SINGLE cylinder is ~US$6,500 + tax - 6 cylinders is ~US$11,500 + tax Those make LN's nickies (US$4-5k for all 6 cylinders) a bargain haha

Hartech is to be thanked for sharing their hard-won information.They issue no imperatives to open your wallet. Glenn is free to consult other experts . With the M96 we rely on the Independents in the after-market to help us. Porsche sure is not going to share information like Hartech offers. Without the solutions that Hartech and others offer - how much would any M96-engined Porsche be worth ? I'll even give credit to Vertex - they give us alternatives and information. Let's give credit where it is due ?

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Damn, are you actually implying that their thrust controlled roller bearing isn't really junk then afterall?

Just a quick note, that the Hartech buyers guide is a little old now and it probably needs to be updated. I know of one statement in the guide that Baz has commented on and has changed his mind on. That's the oil squirters not squirting enough oil on the thrust side of Bank 2. He says that that's not the problem after some testing. I saw a post not to old that said that anyway. I've said it before and I'll say it again, for just in case no one has seen me say it. There is a lot of conflicting information on what causes it. Jake's seen most, if not all of his from cold climates. Hartech has seen it from mild climates/england where it doesn't get that cold. If you really start reading into the borescoring issues, you'll see what I'm talking about. Jake will say clearances causes it, and Baz says it's not a clearance issue but how there is a coolant deficiency on that bank and it's mainly bank two cylinder 5 and 6. Where as Jake sees it on all cylinders. Jake also thinks it's the different type of fuel that England/Europe uses. Also something you will notice is that Hartech likes the closed deck design where Jake and LN still prefer the open deck design on the M96/M97. Anyway, just some food for thought. Mike

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Their bearing choice is not 'junk'. The problem is that Vertex never specifically addressed the objections to the cylindrical roller bearing for this IMSB application. For example,in what way is the mystery bearing Vertex uses superior to the Timken NJ204 (has a Thrust ring) that failed in LN's testing? Is the Vertex IMS bearing superior to NUP204 CTV2C3 ? Hartech does discuss their recommendations and findings.And they revise their recommendations when their further analysis indicates the need for revision. The supplementary oil squirters for Bank 2 being a good example. Nothing like this from Vertex . I have often said that the lack of credible evidence from Vertex undermines a potentially valuable product. The data point from Sapientony is a good example.

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Anyone know if M96 and M97 pistons are forged ? If so, they do swell more than cast ones, are stronger, are ground oval and grow to round, and should have invar struts built into their skirts (as short as they are) to control dimensional changes with temperature. In the old days, forged pistons were looser than cast, and a little noisy before reaching temperature. If M96 and or M97 pistons are forged, then if not set a bit loose at room temp, it can be an engineering challenge to arrive at the right size (with clearances) when running all out on the track at 100 deg F. If set looser, then do these problems go away (give another 0.001 to 0.002 inches to what is already there). But then cold, does the engine have a tad too much blow by and throw a CEL, or will it not pass emissions cold, or will it eventually load up the cats as they take time to swell to the right size ? Anyone know which 3 pistons (bank #) have the wrong offset of the piston pin axis in relation to the bore centerline (increasing torque but also the wear rate (cocking). FSI mentions this and that it was corrected in the 91A engines. Short piston skirts allow for shorter deck heights, resulting for a boxer engine a 2x reduction in width, which can be used by head/valve mechanisms to improve those assemblies. But short skirts and high side loads from high compression engines don't have a lot of surface area to spread the contact patch onto the cylinder wall, so better oils are critical more than in other applications. Is this the same bank that has less than optimal cooling, due to water routing ? When the small block Ford folks bored a 351W to 428 cubic inches many years ago, the Ford big block FE crowd rightly pointed out that they won't last as long, as the piston skirts were raised to the point where the stroke required could be obtained without the piston on the down stroke hitting the crank (stroker) counterwieghts.

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Not everyone wishes to hash out or discuss these aspects on the net, especially if they want to keep it as proprietary info. It doesn't mean they're any less credible or knowledgable IMO. You don't see other successful outfits like Vision coming on here talking about stuff yet they spend a lot of their time building race engines for the various racing series. I don't think anyone owes anyone any info if they don't like to. It's their prerogative. Jake hasn't answered half my questions in the past yet I understand and never feel entitled to an answer. My $.02

LN gave their Timken part numbers & results of their test. Vertex gives no part numbers and no specific test results . Transparency gives people confidence. Rennlist is all about sharing info & results.That is why I suggest credit be given to those vendors who share their knowledge with us.

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As I've said, LN/Flat6 doesn't give out all their info either. I don't fault any vendors for refusing to "give" out any or part of their info as they are a business. I do however expect individuals to freely give out info if they are true enthusiasts. Vertex has been in business a long time and also have repaired many Porsches. I think some people maybe comfortable enough with that aspect without having to know the nitty gritty of every single piece of info, that they may or may not even understand. Any bad service/products and I'm sure we would've heard about it and it would've spread like wildfire in the internet age we're in.