LOKASIL beyond 50,000 miles.

Has anyone seen anything about Lokasil bores becoming OVAL on the 3.6 ? This can't be right. "The cylinder walls in the 3.2 were modified over the 2.7 (which was bored out from the 2.5) to maintain a decent thickness, but the 3.4 and 3.6 are simply bored out further from the 3.2 to obtain the right capacity. This results in a reduced wall thickness and a thinner LOKASIL liner � a cylinder lining system fitted to all Porsche water cooled engines (except the GT3 unit which uses NIKASIL). The metal matrix of the LOKASIL is not perfect and over time they can fracture, and the bores almost inevitably become oval beyond 50,000 miles." Total 911 issue 41. Close-up of the localized Lokasil liner in the M96/M97 block; later revised 3.6 block shown with reinforced webbing. Chris 2002 C2 CAB GT3 Wheels.

That's a very well written statement by that author: "almost inevitably" -- I'd tend to believe anything that guy comes up with. On the other hand, maybe one day our media will actually provide statistically significant objective evidence that supports their dramatic conclusions; until then, it's sell, sell, sell.

Yes, that is what I was thinking too...

So... every 3.6 engine will fail after 50k? Well I guess I better really redline this baby for the next 7,800 miles!

I would question that simply bored out to make a 3.6l from a 3.4l. The liners are inserts and do not have all that much wall thickness. IOWs, there's not a lot of extra wall thickness to machine away before the special cylinder liner material is, well, gone. Even if the liners are bored out, the insert material is consistent in its make up through the entire liner's wall thickness. The liner material serves as a very low friction long wearing cylinder material and is not responsible for adding much to the cylinder's structural strength. The responsibilty for that is with the cast aluminum that flows into the rather porous liner material and surrounds the liner material during the block casting process. Regardless, there are enough 3.6l engines around that if the bores were going oval I think we would have heard about it by now. What's the matter? IMS bearing failure, porous blocks, D-chunk failure in cylinders, sucking AOSs, cracked heads, internal freeze plug failure, cam chain breakage, rod bolt failure and so on not enough to worry about. Now you need oval bores too? BTW, my 02 Boxster 2.7l engine has over 228K miles on its original engine. I suspect bores have gone past oval now and are square... Yet engine still runs good and oil consumption (now up to a quart every 5000 miles) still reasonable. Sincerely, Macster.

Here's a pic that shows the other end of the cylinders, the business end.... This engine out of an older 996 that suffered IMS bearing failure. Engine salvagable. I checked for a lip at the top and bottom of the cylinders. None. Tech told me these cylinders are very long wearing with of course proper oil servicing. Sincerely, Macster.

Well, 200K miles is beyond 50K.... I can live with that.

Macster: Now that is what I want to hear, an “engine has over 228K miles”! I sold my 3.4 996 with 60k and picked up a 3.6 996 back in September. So, what kind of routine maintenance schedule did you use on you 02 Boxster to get over 200k. Chris 2002 C2 CAB GT3 Wheels.

I have yet to tear down an M96 that had 6 totally round and totally straight cylinders, no matter the displacement. The center cylinders are usually distorted the most, especially near the top of the bore. Not all 3.6 crankcases are the same, later units are more reinforced.

Go to this site and read section 2 of their buyers guide. http://www.hartech.org/buyers.html It has an extensive write up on the M96 engines and a detailed analysis of failures including the problem of liners going oval. An interesting read.

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Who are you? Your knowledge is, well, impressive. And your willingness to share is fantastic. Do you sell parts? If so I found my new supplier.

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From page 112 of this document: "Before we start detailing faults and solutions it is important to us to put the incidences of failures reported mainly on the Internet or brought to us for repair � into perspective. We do not know exact National or Worldwide figures but it is very clear to us that most cars have been performing very well with no problems at all for many thousands of miles. No one contributes to an Internet site to explain why and how their car never went wrong and worked just fine � nor do they seem to praise supplying dealers or service and repair centres when nothing goes wrong. So it is easy to read into the complaints that do occur that there is a huge problem � which there is not. We think that the problem really comes about because the cost of repairs (if things do go wrong) is quite high and in some circumstances � higher than previous models � so for some owners it becomes too expensive and hence the complaints we all read about." That is about as clear a introduction to this discussion as I have read. Thanks for the link.

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Just a fan of these cars and want everyone to enjoy his car as much as I've enjoyed mine. Glad I have something of value to contribute. Can't pay back those that have helped me in the past but maybe can pay forward. Not selling anything. Sincerely, Macster.

Just regular (every 5K miles) oil/filter changes and other filters/fluids serviced at regular intervals. There are exceptions of course, we've all read reports of them, but generally catastrophic engine failures are rare. What usually takes an older higher mileage car off the road is neglect which over time turns into a huge repair bill to catch up on what the car needs. Keep the car clean and waxed and looking nice. Makes it easier to justify spending money on servicing if the car looks good. Another reason an older higher mileage car ends up off the road is a failure of an subsystem (like the cooling system) which takes out an otherwise perfectly good engine. A slow coolant leak which can suddenly lead to an overheated and possibly warped or cracked head, for instance. Then one's looking at throwing thousands at an older car, a high mileage engine, vs. putting that money towards a new or newer car purchase. Then too some luck plays a role. As a car ages and gathers miles accidents claim a fair number. An older higher mileage car can with not much damage be declared a total loss. Give a cold engine a moment of idling to gather a bit of warmth and ensure good oil flow, drive car easy -- low to medium low loads and rpms below 3K or thereabouts -- until engine has time to get fully up to operating temperature -- which based on my experience with the in-dash temp gage which is at best a crude indicator of the engine's actual coolant temperature requires the in-dash temp gage be at "180" or thereabouts for some minutes. Once up to temperature then just drive the car. The more time you spend driving the engine at redline the more this shortens the engine's life but moderately high engine speeds with good oil (and a perfectly working coolant system) is relatively harmless to the engine. (I can't tell you in what deserted parts of the country at what speeds in what heat I've driven my Boxster for miles and miles and miles with no apparent harm -- but I can tell you that even high rpms at high speeds and high (100+) temps did not seem to phase the engine.) As a side note, the Boxster may appear to be looked down upon as not a "real" Porsche but but it has as its heart and soul the heart and soul of a real road car and the abilty to cruise as fast as you dare for as long as you dare. You will run out of courage, road, gas, or luck before the car quits on you. Before you shut off the engine give it a moment of idling to shed some heat, especially if you've just come off the freeway or from the track. I try to drive the car every other day or so. I have two cars and sort of split the driving between them. For some times I have owned just the Boxster though and being my only car serves as grocery getter, commuter, grand tourer and just fun car. Sincerely, Macster.

I agree.. Many engines that have come here to be upgraded have done so in perfectly good operating condition and it appeared that the lack of cylinder concentricity really didn't impact them very much.

Is anybody that cleans up the engines reapplying cosmolin to the engines?

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As the person who took that picture, I'll add something to this discussion. Yes, the early 3.6 castings had the same amount of parent material in the liner area on both the water jacket and crankcase side as the 3.2 and 3.4. The later 3.6 blocks are shared with the 3.8, which again the only difference is the thickness of the casting parent metal. There definitely is a difference between the castings. On the later 3.6 castings, I would expect the bores to stay more round than say a 3.4 casting, as we already know that the 3.2 blocks have less issues with cylinders cracking, d-chunking, or going out of round compared to their thinner 3.4 brethren. The walls on the 3.6 are of roughly the same comparable thickness as a 3.2 on these stronger blocks, so I'd expect better life out of them for sure. The later 3.4 blocks (like on the Caymans), do not have these improvements. We see lots of these blocks and it's interesting to see the differences and how Porsche maintains product differentiation to maintain the superiority of the 911. The key to keeping them round is to keep them cool. We joke that the coolant temp light is the "rebuild" light.

When you guys speak of the cylinders becoming out of round, by how much? What is the greatest amount that you have seen and consider it still runable? Also, I'm assuming the out of round is distortion rather than wear, is that correct? Are the cylinders originally finished with torque plates bolted on to simulate distortion from the crank support girdle and heads? Or are they finished in a relaxed state? Could the measured out of round be dimished or eliminated when the motor is fully assembled and at operating temperature? Sorry for all the questions, I just find this motor rather facinating and have since I first read about it in Road and Track in about '96 or so just prior to the first production vehicles being released. The main reasons I bought a Boxster and later a Carrera. TIA

Engines are like bullets. They're only good for one thing, so use them for that intention!

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I always thought of them as a tool

As there aren't any published specs for the lokasil bore that I am aware of, I'd say anything over .002" ovality is too much. Most of the blocks we get here for re-working have at least that much and upwards of .005-.006". The bores are finished straight and that's how we do them. We did tests years ago and found that trying to use torque plates and simulate actual engine parameters was a crap shoot. You get the best results with a bore as round as possible within .0005".

I have always been under the impression that the (M96) 3.4 and 3.6 shared the same 96mm bores, just different strokes. Is that incorrect?

Yes, the castings for the blocks are the same between the 3.2, 3.4, and 3.6. The 3.4 and 3.6 share the same bore size, just the 3.6 has a larger stroke. When they came out with the 3.8, they updated the castings to provide more substance to them for the larger bore size, which then the 3.6 block by default received those upgrades. From best I can tell, the 3.4 engines in the Boxster and Cayman did not receive those updates, retaining the design of the earlier blocks with exception of added windage notches where specified.

I have a 2008 Cayman S and would like to increase the displacement and making it a "bulletproof" motor, but from the sounds of it I am better off scrapping the idea completely. What are the choices here if one does not want a 911 but wants a Cayman?

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You can increase the displacement with larger bores and possibly even a stroker crank. The big bore kits use special sleeves that interlock at the top and create a nearly closed deck which helps strengthen the engine. As for bullet proof aftermarket high performance pistons, rods, crank, and other hardware can go a long way to making the engine more robust. Check out www.flat6innovations.com for info on big bore kits. Uh, check that. I just visited the site and only 2.5l and 2.7l engines are supported. You can give the shop a call though and see if it has anything planned for the 987 3.4l engine. Overseas, there is Autofarm and Hartech both located in the UK. Another path is to remove the stock 3.4l engine and install a 3.6l or even a 3.8l engine from a 997 car, probably one from which the engine has been salvaged. One might even buy one of these engines but I bet the cost would be prohibitive. But as the saying goes: Speed costs money. How fast you wanna go? Sincerely, Macster.

This is not the design that the LN/ Flat Six Innovations incorporates. We keep the deck open 100% as factory..

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We actually offer our Nickies for everything from 2.5 to 3.8L M96/M97 engines and are developing kits for the 996TT/GT2/3 as well as the newer FI engines, but it won't next year before you see anything for the DFI's until it's been thoroughly tested by Flat 6 Innovations.

Thanks for the great info gentlemen. This gives me some things to think about. I have been tossing around going from the 08 to an 09 for DFI but if I can build a very strong motor and keep the 08 I would prefer to do this. I like the idea of getting a 3.6 or 3.8 from a 911 donor car and building on it. Cheers

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Thanks. I've only seen pics of the AutoFarm sleeve solution and the top of the sleeves come together to form a nearly closed deck. I say "nearly" cause where the sleeves comes together they are not fused to each other. Sincerely, Macster.

And so yet another generation of Porsche owners secretly anticipates the day their motors wear out so they can justify a high performance rebuild. It seems the 996 is a 911 after all.

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No problem... Thats what differentiates what we do from the other modifications. Closing the deck has some merit for strength, the Honda guys do it when they are making 800-1,000 HP from their drag engines, but they aren't concerned with cooling characteristics as they run 1320' and shut it down. In a Porsche application where the car needs to maintain the best cooling capability retaining the open deck is essential to cylinder life and thermal conductivity. This is especially true for those who will see track time at elevated temperatures and loads. Not to discount what anyone else has done, because their approach obviously works as well.. Different strokes for different folks!

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Just so it is clear, my impression from seeing pics of a sleeved engine is there were still passages -- gaps -- between the sleeve tops that allows coolant to flow from the head down or over I guess past the cylinders and out of the block. I guess that is the path the coolant takes or does it enter the block and flow into the heads? I would think the former. Your post suggests that some sleeve solutions block the flow of coolant from head to block? If so I can certainly understand your avoidance of a sleeve solution that would result in this. Sincerely, Macster.

Generally a sleeved motor will look no different, except under close inspection one may be able to detect a difference in the color of the sleeve material from that of the case. For Jake: Having seen many motors disassembled, those that have been sleeved from the factory to salvage porous castings, are all 6 holes sleeved, or just the ones where porosity was an issue? Also are the liners cast iron? If not what material? Are sleeved motors cylinders wearing at the same rate and degree of ovality as the Lokasil? Thanks

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Yes, generally, but the pics I saw of the AutoFarm sleeve clearly showed the tops of the sleeves. http://www.autofarm.co.uk/engines/wa...silsleeve_tech Sincerely, Macster.

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There are some members of the industry who are repairing just one sleeve when they make block repairs, the factory also does this as mentioned in the quote above. Generally a ductile iron sleeve is used by the other companies to fix just one bore or individual bores, which generally makes no sense to me, especially considering the differentials in ring capability with the ductile iron Vs. lokisil in the same engine. Lots of these are not working out very well due to the differentials in expansion between the ductile iron sleeve and the parent material, but it is a cheap way to patch up a block for further use. We never do this, LN will not do this even if you request it.. No matter the situation, cause of failure or etc ALL SIX cylinders are upgraded with aluminum billet sleeves and then Nikisil plated. All the way or not at all is the only proper approach, yes it does cost more money, but its a Porsche engine, not a Honda and cost is simply required. Macster, Yes, closing the deck does impeded the ability for coolant to transfer between the crankcase and the cylinder heads as well as between the cylinders themselves. The cylinder arrangement was designed to be open deck, when closed a good portion of the cylinder sees less volume of coolant, especially the outboard portions of the outermost cylinders on each bank. if you look at the closed deck approach you'll see that the hottest portion of the cylinder (top) has the majority of coolant flow severely restricted around most portions of the cylinder. Doing this is similar to machining the fins from an aircooled cylinder as the water must pass over and around as much of the cylinder as possible to stabilize cylinder temperatures throughout the engine. Without clearance between cylinders the coolant simply cannot flow freely enough or at a high enough volume to evenly cool the cylinder. I've attached some photos of one of my 3.6 based 3.8 Big Bore engines with the open deck sleeving arrangement. Its hard to see that the bores have even been sleeved until you look at the back side of the cylinder to see where the parent material meets the sleeve.

Thanks for the pix. Is your 3.8 big bore conversion using iron liners? Just wondering as the color looks different to me than aluminum and I wouldn't think a plated bore would be honed. Just guessing as I haven't worked with plated bores. Also I assume the sleeve at the deck is flanged to eliminate potential movement? One last question, are all cylinder failures or most that you have seen due to a factory re-sleeve issue, or does the cracking, breaking also happen with virgin as cast and finished bores? Thanks

NO! Those are aluminum liners constructed of billet extrusion. We do not (and will not) use an iron liner. . The color difference is the Nikisil plating... Those liners are honed, the resolution of the camera and lighting do not allow for the super fine finished hone to be pictured very well. You can see some cross hatch patterns, but not very much. No flange is utilized. The method utilized to fix the sleeve to the parent material is proprietary to LN Engineering and took at least two years to perfect. Honestly as their partner in development not even I know the exact method utilized. These days we seldom see OE engines with cracked sleeves/ cylinders. Most of these that were going to fail, have already failed. The biggest issues were with the '99 MY engines that were "repaired" from the factory as new.

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Jake, I was going to ask how are the sleeves retained, but you answered it. What is the biggest the 3.4's can go to (3.6/3.8)? Thanks Rick 99 996C4 87 944S

3.6 with bore alone, or 3.8 with a crank swap.

What else would be required to turn a 3.4 into a 3.8 when I rebuild? I would assume a tune and cams at least? Regards, David

Found this interesting read the other day from Hartech. They claim to be able to overbore Lokasil (and replace/weight match pistons) instead of reboring/resleeve with Nikasil liners (or cast iron). http://www.911uk.com/viewtopic.php?p=633086 "We have matched weights etc so it is possible just to fit one piston if the others are still OK - then with the extra cooling mods we do the others should run OK in the future. Our solution of just overboring the existing Lokasil and fitting securing rings while lowering the running temperature in the cylinders by reorganising the coolant flow and fitting a lower temperature thermostat - is the best way to go long term and also the least expensive - so I cannot see what advantage iron liners have (except they are less expensive than the Nikasli alloy liners we used to fit before we developed this overboring solution). " - Hartech

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Apparently, there aren't any liners in the engine. This was called out in "the book" as a misnomer. The apparent misunderstanding came about due to poor translation from the German to the English. I'm just stating what "the book" says!

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From the link I posted above yours: "The water coooled Carrera's have NO liners. They have impregnated Lokasil, the hybrid cooled GT3 and Turbo (+ derivs GT2 etc) have aluminium sleeves coated with Nikasil. The Lokasil is a silicon hardening process for the aluminium castings. Porous cylindrical shells of silicon are aligned in the cast where the cylinder walls will be and when the molten aluminum is poured in it reacts with this LOCAlised SILicon matrix. The silicon "bleeds" into the local surrounding aluminium. The cooled cast is machined and acid etched to create smooth and hard cylinder walls. Because the Lokasil is part of the cast it cannot "slip". As the GT3, Turbo (GT2) are hybrid cooled (water cooled heads, air cooled bottom ends and cases), they have a different design so the air, oil and water stay separate. The case has a sealing liner coated with Nikasil. (NICkel-SILicon carbide). The incredibly hard Nikasil was first used by Porsche in 1970 for the 917 aircooled engines to allow smaller engineering tolerances, allowing greater pressures and bigger power. One problem the Lokasil engine design can have is catastrophic edge failure. The casting of the tube (cylinder wall) is squared off at the end. By this I mean the tube just ends perfectly straight. This means a very sharp right-angle edge with the associated point stresses and aerodynamic/hydrodynamic vortices. The edge can get fatigued and break off, this in itself is not ideal as piston sealing may be jeopardised, the real issue is where the broken cylinder wall fragments end up next in a fast moving engine. The debris will destroy the pistons, conn rods, crank shafts etc and complete engine destruction ensues. Fortunately it is pretty rare. A more common failure of the casting is not related to any liners or lokasil etc, it is the thin walls associated with cross-flowed water cooling and large bore. According to Hartech, eventually ALL water cooled Porsche flat sixes will become ovalised over time (warped). Including Boxster. For both, the solution is a re-bore with liners. Replacement Hybrid Nikasil liners have with rounded/tapered edges to prevent the edge stress."