[Lear35A]

On April 3, 2010 I started a thread on rebuilding my 968 engine. http://www.968forums.com/topic/9236-968-...rebuild-1/ This was required due to a crack in a cylinder wall. After a lot of work, a bit of money and a long time, I thought I'd done it. However after 100 miles, it was clear I'd blown a head gasket. I suspected that either I'd stretched a head stud or a stud was pulling out of the block. I pulled the head, bought a new set of studs, crossed my fingers and put the head back on. A couple of nuts around cylinder 4 did not torque properly, but I finished putting it together just to see. The head gasket blew almost immediately after engine start.



So I had to pull the whole engine out and take it apart again. I took the block to a racing shop that drilled and tapped the 10 stud holes, put in inserts and ordered American 1/2" racing studs with 12 point nuts. The head will be torqued to good old foot pounds, not angle torques. It can't be any worse.



I got everything back tonight and started cleaning things. I'll take my time and report here how things are going. This car has been down a long time. I sure hope this time the outcome is better.



As before if anyone needs a picture of any internal component let me know.

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[Cloud9...68]

Lance,



So sorry about your misfortune, and here's hoping for a great outcome this time.



My engine is still in pieces, with the crank at one machine shop for cross-drilling (I was advised to do this to improve oil flow, since the car is going to be tracked extensively when I get it back together), and the head at another shop. The weeks are turning into months; I've made good use of the time rebuilding the rear suspension, but that's done, so I'm getting frustrated waiting for the machine work to be completed.



Because of the long interval that's passed since I stripped the engine down to the bare block, I'm getting concerned that there will be elements of the re-assembly that will leave me stumped (I took a lot of pictures during the disassembly, but not enough, I fear), so could you do me, and anyone planning on rebuilding their engine in the future, a big favor and take lots of pictures as you put it back together? I'm sure you already have a lot from the last go-around. When I finally get my parts back, count on me bugging you a few times to guide me through the parts of the process that I'm sure will leave me with questions!



Again, best of luck with everything. You're definitely going to be the resident engine rebuilding expert!

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[Scott Collins]

Lance,



You're putting in a tremendous amount of effort. That's got to be frustrating. I'll keep my fingers "crossed" that the 3rd time will be the last time.



-Scott

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[tamathumper]

Hang in there - that's the kind of frustration that can make you swear off the Porsche platform for a decade or two. What kind of studs did you go with, brand and material?

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[Cloud9...68]

I wonder how common problems with the studs are... I'm tempted to take it to a reputable local shop to "look things over" at one or more key steps of the re-assembly process.

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[RS Barn]

Studs were a real problem on 951's The typical problem was having the stud pull on final torque . Then you have a mess to deal with-complete dissembly first then fix stud. ARP sells a replacement stud kit but removing all the studs is a problem. Getting to area to fix stripped holes is another. They aren't bottomed in block but Lock tighted in. I strip block completely and put in big oven @ 300f for 2 hours. Then the studs can be removed using double nut method.

Installing studs is actually one of the last things you do on a rebuild. Assemble bottom end complete/have head ready to go. Use correct Lock Tite on threads, finger tighten studs to correct depth, install head and torque. Torquing the stud sets the locktite.

I only use torque angle method

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[94SilverCab]

[quote name='RS Barn' timestamp='1309889629' post='112230']

...put in big oven @ 300f for 2 hours...[/quote]



Sounds like roast pork loin...<img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />



Sorry, couldn't help myself,



Jay

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[Lear35A]

If a head has been off multiple times be cautious about this issue. Torquing the head pulls a steel stud against an aluminum thread. As Pete points out, you don't know you have the problem until the final torque. If the stud starts to pull out, it means stripping the block down to nothing and starting all over. To drill, tap and put in inserts is a big deal. It's best done on a CNC mill and takes some special tooling because the threads are recessed so deeply in the block.



I'll find out the specs on the studs I will now use. Since I have this type of stud, I am going to a pure foot pound final torque. If it's good enough for a 1,000+HP racing car, it's good enough for me.

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[flash]

yeah - there has to be a better way than what they did - we used to have the same kind of problem with the british stuff, and ended up with better studs and inserts - on some engines we did "through studs"



the first time i get a block apart i'm going to dive into that myself - that torque angle crap has to go

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[Cloud9...68]

The fact that Pete mentions studs being a problem on 951s, and yet I haven't heard of any issues with the 968 other than Lear35A's (although I'm sure there have been plenty of instances) gives me hope that problems are in fact pretty rare. I will use extreme caution during this (and every other critical) step, and tear it back down if it isn't torquing properly.



Reading through Lear's original post again, I just caught the fact that he replaced the studs after the first rebuild, and they still didn't work. Ouch, scary stuff.

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[tamathumper]

I remember when Dilavar and Raceware studs were all the rage - then the Dilavar studs started breaking due to mid-length corrosion IIRC. What's the state of the art now?

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[Cloud9...68]

"[color="#1C2837"][size="2"]What's the state of the art now?"[/size][/color]

[size="2"][color="#1c2837"]

[/color][/size]At this point, I'm hoping it's whatever Porsche put in these engines 19 years ago

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[Lear35A]

Made some assembly progress over the weekend.

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[Lear35A]

Caught a big screw up today. I was timing the cams which requires you to turn the engine over many times. The spark plugs are out so it should turn relatively easily and smoothly. But it wasn't. It was difficult to turn with a wrench on the front pulley, and it wasn't smooth. It would stick and slip. What had I screwed up???????



After looking around some, I found it. The bearing caps on the cams are bored in place when they are manufactured. Therefore they must be put in the original location. Porsche makes it easy by stamping a number on the bearing cap and the matching number on the head. I had all the caps in the right place, but one of them (#2) I had put in upside down. I flipped it over and the engine turned over like it should.



Whew.



Second picture is current state of assembly. My plan is to try to get it in the car tomorrow. <img src="/forum/images/smilies/968/unsure.gif" class="smilie" alt="" />

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[Cloud9...68]

Wow, congrats on finding the problem, but this is scary stuff. How many dozens of pieces are there that could easily and innocently be installed backwards, or otherwise incorrectly, resulting in catastrophe? I am going to treat this thing like brain surgery (and even that won't be any guarantee of success). Man, could I get any more nervous...?

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[Lear35A]

It's really not scary or hard, but there are a lot of parts that are happier when they go together correctly. Be prepared to do some steps more than once to get it right. I'm just airing my dirty laundry in this thread because it's kind of therapeutic <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" />

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[tamathumper]

Another reason I'd want to do this work myself, or rather, I would *not* want to do it myself but I don't have the requisite faith that anyone "in the profession" locally would do it perfectly either.

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[Cloud9...68]

Lance,



In addition to being therapeutic, your posts are very helpful to those of us (although it sounds like I'm the only one in the situation at the moment) in the process of doing a rebuild to alert us to potential problems. And it's exactly the multitude of parts that has me concerned. Fortunately, in addition to your experience, I have a couple of guys in the neighborhood who have recently rebuilt engines, including a 944, to lean on.



I recently took my rear suspension apart to install solid bushings everywhere. On a scale of 1 to 10, this job rated a 9.5 in my book in terms of difficulty, danger (I have the stitches and staples to prove that ), and just plain effort, but it dealt with a relatively small number of parts. The engine is a whole 'nother kettle of fish. Hopefully, once I'm knee-deep in it, it will all make some amount of sense.

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[Lear35A]

Engine in the car, but still a LOT of things to hook up. The German engineer who designed how the torque tube connects to the bell housing is not your friend. The top two bolts are virtually unaccessible.

BTW I got it in all by myself. I don't necessarily recommend this, but I did not have the heart to enlist any of my friends on what is a beautiful Sunday in Atlanta.



Edit: Why does software turn all my pictures sideways? <img src="/forum/images/smilies/968/mad.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/mad.gif" class="smilie" alt="" />

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[Cloud9...68]

Wow. I am not worthy! I am not worthy! That's an impressive feat. I hear you about the top two bolts on the torque tube. As I was removing these, I was already dreading the moment I would have to try to finagle them back in. And this is the third time for you! Good luck with the rest of the hook-up, and with the tense moment of firing her up!

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