IMS Bearing failure recovery and cylinder head condition

Hey guys: Lets say an M96 experiences IMS bearing failure (causing cam sync codes and a quantity of metal in the engine oil). A logical choice seems to be picking up a factory Short Block 3.6l and reusing the existing heads. But is it possible that the heads and particularly the cams might be junk because of the metallic particles in the oil? How much work is needed on a (lets say) 80k set of heads to get them ready to bolt onto a factory short block? Anyone with experience on this subject? PS: On a related note :-), opinions on the value of an 80k mile 2002 Carrera 'roller' (in apparently excellent shape otherwise) but with IMS failure? I'm mulling over such a car to replace my recently stolen C4S.

If you had a working oil filter that didn't operate in bypass mode (so either had the mod yet or the spring of the original canister was in good condition), metallic debris will not have reached your cams.

4-6K for a roller....I have seen some people get them for less but those are rare....I have not seen anyone pay more though.

In my experience and observation, between $4K and $7K. That $4K was on the board here (808Bill), and is the least expensive roller I know of.

Yes, metal can get into the heads. Could have damage to the cam tower cover bearings, bearing caps, and cams. Hydraulic actuators, lifters, and oil pumps.

Like I said, only if his bypass valve was faulty. They can go bad easily, but if it's been good metal debris can't make it to the heads / bearings / lifters etc.

I could have got it for three if I tried...But, I felt bad for the PO.

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If the car has the stock oil filter, it is likely there was some bypass if the car was run when it was cold and the oil viscosity was high. If you look at the pressure gauge, the indicated oil pressure is around 5 bar when you first start driving, even under low load and rpm. One of the advantages of the spin-on oil flter is there is no bypass. If you drain the oil from the sump and there is glitter in it, then you can expect to find particles all over the engine. The heads would need to be completely disassembled, cleaned, and inspected to see if they can be rebuilt. The LN Engineering folks know the answers to all the questions related to IMSB failure and subsequent rebuild. They have seen it hundreds of times.

BTW Silvergray, I know of a red 996 C4S in seattle that will be for sale in the next week or two...The guy opportunistically bought a beautiful yellow 996 turbo and is preparing to sell his beloved C4S....IT has some suspension and exhaust modes but he will sell it either stock or with mods. If you are interested I can get you connected before he lists.

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Are you sure about that? The bypass only opens if there's a considerable pressure difference between both sides of the filter media - the absolute amount of pressure doesn't really matter as long as your filter media isn't clogged. Even with thick oil, that pretty large filter media flows plenty - otherwise the Napa Gold filter (which is smaller) would damage the engine during startup since it has no bypass and would starve for oil. They both flow plenty. Only with a faulty valve do I see debris making it into the pressurized oil system, as metallic debris will only get sucked up when a continuous stream of oil flows through the bypass for a longer period of time. If your bypass works and your car has been sitting for a while (cold oil), metallic debris will also have long sedimented towards the bottom - it will not be floating around in the oil. I only see a properly operating valve opening during the short transient when the engine is started since there is 0 oil pressure in the engine at that point. This event only lasts for a second or so - during that time the sediment will not have come loose from the bottom of the oil filter canister yet. Sedimented bits in oil really 'stick' to the bottom unless a high-velocity continuous stream of oil is blasted over it - by the time pressure has built, oil will go through the filter media rather than through the spring-loaded bypass. Road of less resistance. I know what LN engineering recommends, but I don't generally buy into the stigma. It's a business for them, so of course they will keep recommending the engine to be fully taken apart and inspected. If I were specialized in these engines, I too would want to make sure public opinion would be that "after failure the engine has to be completely rebuilt", so I'd get more business. And they've been very successful at it, since every IMSB thread is instantly hit with exactly this sentence as in this thread: It's been deemed the absolute and only truth, even though it need not be. My engine is the living proof of that and it ran with grit in the oil for a good while. Haven't seen any of it return in the past 3k km. Don't get me wrong, rebuilding the thing is solid advice and will in 100% of the cases give you a working engine if you let LNE do it. And even if no metallic grit made it in there, all these engines are worn so there's always something for them to do while in there, can't really go wrong there. But it means big $$ too. From a business and marketing PoV, I totally get it, but from an engineering standpoint it does not always make as much sense. I'm not taking a stab at LN, they are very knowledgeable people, but you guys have to realize that they are first and foremost a business for profit. They absolutely give the best care for your engines, but some people are looking for a middle ground that will just make their engine run relatively reliably at a lower cost instead of 'like new' for basically the entire value of the car. After all, OP asked if his parts had any chance of being reused, and I'm confident that there is a good chance grit didn't make it into his pressurized system if he stuck to regular oil and especially filter changes. If he adhered to Porsche's 30.000 mile interval recommendation, eh, things might look less good.

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Doubtful the heads are ruined, they will need to be ultrasonically cleaned, cams etc will need to be inspected & lifters will need to be replaced. Might as well have the heads rebuilt during the process. I just sent a good 2002 3.6L case to LN see if you can buy it from LN.

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Umm hell yeah! My favorite color! I'd be most grateful if you would put me in touch. I'll see if I can send you a message... Cheers,

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This is the first sentence from the description of the spin on oil filter adaptor from the LN Engineering site: The LN Engineering Spin-On Oil Filter Adapter helps improve the longevity of your engine by providing full flow filtration by deleting the bypass, which means 100% of the oil gets filtered and whatever goes to the filter stays in the filter. This limits collateral damage from foreign object debris that would otherwise re-contaminate the engine when using the factory filter arrangement from wear particles or debris.

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Ah, that settles it. Didn't know marketed sales descriptions were considered fact, as by no means fortunate omissions could be used to sell a product. I'll be on my way, then.

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Its true that marketing is often deceptive, but in this case, the LN Engineering folks are widely recognized as experts on these engines. If you search in the threads, there is discussion with pictures related to the design of the stock porsche oil filters. There is history on the design too. I have a porsche 356 with a paper filter. The 356 engines are based on the old VW engines. They also have bypass flow. There are also adapters you can buy for the 356 to install modern oil filters, although I don't think LN Engineering sells those.

Back to the original question: Based on my experience, I think there’s a good chance your heads and cams are fine. The car I bought had a major failure of the number 6 connecting rod bearing. I don’t know how long the previous owner ran it, but it had glitter in the oil canister, glitter and chunks of bearing material and steel in the sump and stuck to the oil intakes. The con rod was running metal to metal on the crank, and the crank was heavily scored. I had the same concerns as you, so sent the heads and cams to Hoffman and asked him to check them and give me his opinion. He cleaned them, did leak tests and pressure tests, and surfaced the gasket surfaces. Bottom line was the cams and bearing surfaces, and valve guides were in excellent shape, in fact he told me he’s seen heads in much worse condition from engines that had not suffered a failure. I installed them into a new short block and the engine is running perfectly.

The crankcase is actually connected to the heads by the cavity for the chains. I had metal from the crankcase get into the heads while using a no bypass oil filter. Posters should be be a little careful with absolute opinions, especially when they are absolutely wrong.

I was just relaying my experience, other experiences may have different outcomes.

Coopduc, if your post was addressed to my last post, just wanted to clarify my post was not addressed to you specifically. Saying a failure in the crankcase absolutely does not affect the heads is wrong and I think it would be wrong to lead listers to believe so. Yes, you can gamble, but anyone repairing their engine should know there is a pathway for debris to get into the heads. IIRC, the detergents in the oil actually captures/carries debris to take it to the sump as opposed to break in oil which allows debris to drop out. An engine rebuild is expensive and is a good example of insanity. So everyone that partakes in dong so should at least know what the risks are so there isn’t a second failure sooner than expected.

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PM'd contact info of seller and also called your cell....

@tomcat - understood, no issue from my side. In any event, heads and cams absolutely should be checked after an engine failure, but not automatically assumed they are damaged.

I'm in the camp of the heads will be ok. No need to squabble about it, no one will know until it disassembled and inspected/measured.I've been a dealer Tech for over 40 years and have seen the inside of many engines with debris of all kinds and all amounts. Debris usually kills the rod bearings or main bearings first, the heads usually survive (unless there is a catastrophic failure like broken rod or dropped valve). What usually kills the heads is dirt or very small debris, less than 10 microns (that the filter will not catch anyway) over a long period of time that will wear the in-head cam bearings.

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It *is* deceptive though, as that paragraph you mentioned makes it seem that the original filter configuration 1) isn't full-flow by design (which it is) and 2) will absolutely send debris into your pressurized system. Both of which are simply not true as long as your bypass valve isn't faulty. The bypass valve is a risk factor, but certainly doesn't have a failure rate of 100% as implied. That's the whole thing I've tried to detail in my post. Which is why I think OP's heads have a good chance of being fine. @tomcat, nowhere did I say his head will absolutely be fine so don't put words in my mouth, thanks. The chain-pathway is a possible one, I addressed the pressurized path from the oil filter though. Afaik the cams are pressure fed, so debris will not flow upstream of that. How is that an 'absolute opinion'. It is possible to be widely recognized as experts and be a business at the same time you know.