[Lear35A]

So for the third time within a couple of years I am doing a complete 968 engine build. Between complete builds I've had the head off a couple of times. I posted about the cracked #2 cylinder wall that started all of this earlier. Look it up if you're interested.



The repair I tried was a straight dry sleeve. To make a very long story short the crack reopened and the sleeve did not have enough wall thickness to make a good seal with the head gasket. The symptom was coolant getting pulled into this cylinder. Anyone who wants the details feel free to call or PM me.



In retrospect I should have tossed the block at the beginning. Once I got more and more into it, the block became more and more worth keeping. And really there aren't all that many true 968 blocks floating around at a reasonable price.



This time I really bit the bullet. My shop installed Darton wet sleeves in the block. This entails milling all the old cylinder walls out. It's major. You can find YouTube videos about the process if you're interested.



I got the block back this afternoon. I'll clean it this long weekend and start the rebuild process for the third time. I do intend to post how it goes.



The Darton wet sleeve has some good racing references in many types of motors. I don't know how many 968 there are out there with this mod. Hopefully this is the last time I have to do this.

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[flash]

i almost went that route. the problem i had, was that due to the open block nature, there was a potential for movement under boost and at high revs. for a stock street motor everybody felt it would be fine, but knowing that i was boosting, and going to rev the piss out of it, it was iffy. i did not want iffy. i really wish i could have done it though, because i wanted to oversize the engine a lot.



please do let us know how it goes. i am very interested to know if i made the right call or was just paranoid.

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[Monstrous4Banger]

Im also very interested in this. I have a spare 2.5 block I may use to sleeve, instead of modding the 968 block. The sleeves do a pretty good job of closing up the deck.

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[Cloud9...68]

So if I understand correctly (and I'm just guessing, based on the names of the two processes), a dry sleeve is a thin insert that retains contact with the metal from the block all the way around its outside, and a wet sleeve is a thicker, more elaborate sleeve that contacts the coolant on its outside. Is this close? My guess would be that dry sleeves are used in the case where only minor repairs are needed (such as scoring of the bores that's too deep to hone, or more likely, a small crack), while a wet sleeve would be used to correct a more severe problem.



What are those small holes drilled in that interesting pattern in the sleeves?

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[Monstrous4Banger]

Dry sleeves are liners, wet sleeves are a replacement of the cylinder all together. Cant hone on alusil really. More of a chemical etch. Im not really sure what the holes are for.

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[Cloud9...68]

I believe that alusil can be honed. It's a chemical/mechanical process requiring a special slurry, specialized equipment, and a lot of skill, but it can be done.



http://www.lindseyracing.com/LR/Parts/944MACHINE.html



Otherwise, installing dry sleeves would entail a significant reduction in displacement, not to mention the need to do all the cylinders, not just the one with the problem, and would of course require a new set of pistons. I believe Lear35A had a dry sleeve inserted just in his one bore with the crack, if I'm not mistaken.

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[Lear35A]

The holes are simply passages for the coolant flow. I assume the pattern is designed on a Cray supercomputer.

Today I am helicoiling about a dozen M6 holes. These are in the oil pan, oil pump and balance shaft cover areas. I can tell you, repeated torquing of these small diameters weakens the threads big time. Nothing more frustrating than torquing down the oil pump and have the last screw put out the threads. So fix it now, right?

I am also cleaning the block. It's a very time consuming process to do right because there are so many coolant and oil passages, nooks, crannies and other places to trap metal chips, honing fluid and other nasty stuff.

I'm sure glad it's going to be mid 90s today. Saves on the sauna bill.



And no, after the first crack I had all four cylinders with dry liners. The other 3 cylinders sealed fine, but in retrospect I know the crack was unrepairable. To put in the wet sleeves all the old cylinder bores are completely machined away. They put these Darton sleeves in very high horsepower, think 426 Hemi, and in very high revving, think rice rocket, motors. I really don't think anything is going to move in my little 3L 6400rpm machine. Even with the supercharger. We'll see.

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[Cloud9...68]

Ah, so you did all four. I was mistaken - for some reason, I thought you only did the one with the crack. Best of luck with everything this time around.

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[Lear35A]

Had to put something together to avoid depression.

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[Monstrous4Banger]

From what I understand of it, its not really a honing process in the traditional sense. Yes it can be done, but its more of a chemical etching like you said, as oppose to actually honing.

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[flash]

traditionally wet sleeves are not put into an open deck engine like ours. that is where the problem will lie. i was all prepared to send the motor to darton, but when i told them what i had in mind, they would not guarantee that things would not move.



i hope this works.

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[Joel968]

Running Darton Mid sleeves in my 3.1 turbo. Darton did the install, no issues!!! This will also open you up to a larger range of pistons and rings.

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[flash]

i sure wish i had known about that before. funny that darton did not mention that when i talked to them. did you start with a 944 block or a 968 block? the problem as i understand it is that the 968 block is open deck, whereas the 944 block is closed deck.



this is exactly why i wanted to do it though. it would have allowed me to run bigger pistons. the problem they were afraid of when i spoke to them was the boosting. they may just have been scared, but the concern was that there was nothing to hold everything in place, and as the block and sleeves were dissimilar materials, they would heat and cool differently, and under boost might open the door for leaks and such.



frankly it would have been cheaper and faster for me to have gone the darton route. i still don't know if i chose correctly or not. i will be very interested to see how this works out.

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[Joel968]

968 block and it was done at the east coast Darton shop. They never expressed any concerns with me about the install and fully support, promote the mids in the 968 block on their website. http://www.darton-international.com/we_install.htm Might be something that they started when the opened the shop in Va.

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[flash]

weird that they didn't feel so good about it just 2 months ago. i know they said they weren't confident. maybe they have had failures. i don't know. i know somebody who did it themselves that did, but i have no idea about anybody who had darton do it. i was going to send it to darton out here in carlsbad. they are practically in my back yard. it seemed so easy, right up until i started hearing about problems. i was fully prepared to live with the shorter lifespan of sleeves and such, but not head gasket issues.



don't get me wrong, i love darton, and used them quite a bit in years gone by. they have saved me more than once. it was initially my "go to" solution to my current problem. it was only this engine that i ever heard anything weird about. i don't have enough information to really determine what the story is, but i just didn't have the time or energy to be the guinea pig on this one. i already sacrificed one motor to the development gods. i didn't want to do it again.



i sure hope this works. lear has had enough troubles.

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[Lear35A]

I'm glad to hear a fellow Gawhjen had good luck with Darton in a 968 block. My shop got a lot of support on the machining and install from Darton. It looks beautiful, but only time and boost will tell for sure. This won't be a fast build because I have so many other things going on. So I can't predict when I'll be on the road again. I must admit, though, I am anxious to find out.

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[Monstrous4Banger]

Yeah Ive heard nothing but good things about the wet sleeves. I had the same questions when I poked around about it. Chris White(944 enhancement) was very confident my concerns wouldnt be an issue.

944 is a open deck too, as well as 968. All the blocks are very similar, the biggest difference besides bore throughout the years is the coolant passages on the s2, and 968. S2, and 968 block are the same except the 968 block has piston squirters stock. I would think with the sleeves closing the deck up like they do, you could run gobs of boost. Long as the sleeves stay put.

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[flash]

i spoke to chris too, and didn't get a confident response, due to the boost issue. movement was the concern.

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[Monstrous4Banger]

Hmmm, I had the same concerns you do about it Flash. I am very interested to see how this turns out. Ive heard a few people who have had them that havent had an issue yet. Ive yet to hear anyone have an issue when done right. Doesnt seem practical to DIY it. You have to put the block in an oven to fit the sleeves, I could easily see it failing if its not done right. White seems to have the most experience wet sleeving our specific blocks. When I talked to him, he didnt seem concerned. How much boost do you plan on using? Sleeves, or not our cylinders are known to wiggle under heavy boost. Seems to me it would wiggle less with wet sleeves. In other words, if your worried about it wiggling with wet sleeves with your desired boost pressure...it probably defintely will with the stock cylinder, and deck. I seem to remember someone making a deck plate though.

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[flash]

yeah - he worked on it with them.



my concern, as was the one my builder had, was that the sleeves are not really connected to anything. aluminum expands differently than steel, and even more when you remove the interconnecting material. the dissimilar materials meant that there could be gaps forming during heating and cooling periods. proof of that is that the block had to be heated for installation. this was to create the tolerance to install them. what do you think happens when the engine gets hot again? hello. tolerance again.



that made me nervous. it would take very little movement under boost to create a failure. if these things were welded in or something positive, i would feel a whole lot more confident.



i'm not saying it won't work, but i didn't want to be the one to find out. darton is a great company, with a great product. i'm just not at the point where i want to experiment much these days. i've been doing enough of that.



as for how much boost i plan to run, knowing that boost is a relative number based on in and out flow, since i now will have a bottom end capable of it, i tend to think i'll push it up a bit. we'll see how it runs on the existing level. i bumped the compression up a touch, so as to improve bottom end (pre boost). that should make a bit more power overall. i'm not worried about detonation, due to the nature of the centrifugal unit, and my ability to tune around it.



but enough about my motor. we can talk about that in another thread.



i am also VERY interested to see how this turns out. i would still like to do a 106mm engine with standard shaped pistons, and 8-9 lbs boost, and that means these sleeves.

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