blue44

I'm thinking of replacing my '93 968 ( 103K mi ) head gasket in my garage ( previously losing coolant, overheated during driver's ed at lime rock, got the white smoke last start-up ). Right now the exhaust manifold studs ( do they have to be replaced ? ) and the timing belt are the questions. Recommendations ? thanks...

RajDatta

Blue, 1st you need to determine the cause of failure. Is it the head gasket or something else. I would suggest removing the head and getting it checked out. Also, with your mileage, the head is probably tired and could use new guides and seals. There should also be some pitting from corrosion which would need to be filled.
I have never had problems with old studs but fatigue can be a factor with them going through so many heat cycles. I always try to use a 6 pointed socket to even the amount of torque.
Also, how many miles on the belts? If they have atleast 30K and 4 yrs on them, I would say, swap them.
Your best bet is to cut the middle man and find a machine shop that can do all this. No point in making vendors rich when the actual work is being performed at the machine shop. I know of an excellent machine shop that our local Porsche dealer uses. Cuts the price down by a lot.
I am sending you an email with information.
Raj

whakiewes

Definantly possible to do at home. Rebuilding the head would be of a much more tedius and time consuming task, but doing a headgasket is a fairly simple job. Right now would be a great time to spend a little money though. The 968 head sees good benefits from a little porting/cleaning work. Pete at RS Barn offers services, or you can get a lot done at your local machine shop. This would also be a good time to do new exhaust studs, exhaust manifold gasket, intake manifold gasket, valve cover gasket, front end gaskets, rollers, and all new belts. Cheap maitenence for the future.

Generic instructions for the headgasket -
Remove front plastics, airbox, MAF meter
Jack car up, supporting it by quality jack stands (this could go first, it doesn't (matter).
Crawl under the car, and remove plastic undertray (the large one)
Find the two manual tensioners, one for the AC/Alt. belt, and one for the PS belt. AC is 17mm, PS is 13mm.
Loosen both until you can easily remove the two belts, PS V-Belt may take a little force.
Remove fans (six bolts, 3 top 3 bottom, 10mm, and this is subjective, I like the extra space and it takes 5 minutes, not required)
Remove front cover plates, about 10 or so 10mm bolts, two pieces, lower and upper.
Remove distributor wires, then cap. Flat head that turns to release, or an 8mm.
Now the balance shaft and timing belts, rollers, etc... are exposed.
At this point, it would be good to insure engine is at TDC. There is a mark on the cam gear, which aligns with a mark on the head. Don't worry about balance shafts, they will have to be retimed when everything goes back together. The bottom end only goes on one way, at TDC, so you can't really mess that up very much.
At the main crank pulley, there is a guide rail that has to be removed, two 10mm bolts.
At this point, to remove the belts and guide rail, you must remove/loosen the engine crank nut and remove the main pulley. This takes some brute force, torqued at something like 300ft/lbs. Best is to use a huge breaker bar with an extension to get as much leverage as possible. If you don't have a flywheel locking tool, but the engine in 6th gear, E-brake tight, and lower the car back down on the ground. Its going to take some work to get loose. May have to call a friend to help out on that.
Once that is loose/off, the balance shaft belt is loosened by an eccentric at the lower left hand side of the engine. Its a 26mm or 1 1/16, and a 17mm bolt that keeps it tight. Its very easy to understand. Remove the BS belt. All the rollers are held in by varying bolt sizes, no real work involved. Timing belt is a little harder. We have an adjusting hydraulic tensioner, which has to stay tensioned.
Remove the tensioner. I can't really help much here, as I just followed the workshop manual which shows how to keep it tensioned. I think it just says put it in a vice in the worst case.
The timing belt will now slide off. You may have to remove the main cam gear to remove it, and/or install it.
Now the head is free from the block.
Remove valve cover and injector cover.
Remove intake manifold from the head, and set it aside (unless you are planning on doing some porting work)
Remove the exhaust studs...this can be exhausting, be patient.
Follow head removing sequence which I can find, but I don't have it memorized.
Replace headgasket, making sure you clean the block and head to insure a good seal. It really is beneficial to have the head rebuilt at this point.
Reinstall the head, very carefully...Al bends easily. Make sure the head and block are at TDC by the corresponding marks. The cam gear and crank pulley only go on one way, at TDC, so if you remove either, you are plenty fine.
Following the torquing sequence (again I don't have it memorized).
One last time, check and insure your head and block are at TDC.
Reinstall timing belt, tensioner keeping tabs on the correct tension, and balance shaft belt. Tensioner may require replacement, fairly costly.
Tensioner will tighten the timing belt correctly.
Time the balance shafts. There are marks on both which show their relation to TDC. They are both cutouts, and you can see them both.
Tighten the balance shaft belt using the eccentrics. Its best to have a tensioning tool, but you can probably make it work regardless. Don't have tighten/stretch the belt, don't make it too loose.
Do the reverse of the above instructions from here on out.

Very basic, but it should help some.

Wes

RajDatta

Your best bet is to buy a head gasket kit. A lot of places sell them including Sunset Porsche and everything you will need is in there. Takes away a lot of guess work.
I have bought them from Sunset and from EBS Racing, just to compare and both are made by the same vendor, Victor Reinz. Prices should be appox $180-$200.
Wes, there is no way a vendor would ever be able to give someone the same price as going to a machine shop. How can that be, they are in the business to make $$$. If they were to pass you their cost, they would be out of business. All the work is performed by the machine shop for such a task.
Regards.
Raj

whakiewes

Raj,

I agree. I have never paid for a middle man to pass on the work. For the people that have no idea where to start though, it helps. FWIW, last time I had my head rebuilt, new guides, cleaned, sonic tested, it was about $350. The vendors, RS Barn, Lindsey Racing, etc... don't perform the work in house...I understand that. But like I said, if you have no where to go, it helps.

Wes

RajDatta

Also, there is a lot of options that exists besides what we read on the web. There are quite a few places one can get performance head work done. Most of them are too busy to bother coming to web forums.
Raj

blue44

Thanks for the pointers, guys. Maybe I'll take it over to my mechanic to get his recommendation. Doing the top and front of the engine seems like a pretty big job. One more thing ( well, two ), do you safe the ignition system somehow when you do a compression check ? Second one is to turn the engine to TDC, do you put a wrench on the crankshaft nut ? Thanks...

RajDatta

There are no issues with doing a compression test.
Yes, use the 32mm bolt to turn the crank.
To swap the headgasket is not that hard. I know of atleast 3-4 people that did this themselves and they were average weekend wrenchers. You have us here in case you run into a problem.
Good luck.
Raj

whakiewes

Headgasket is definantly a DIY job, just a careful and slightly time consuming one. Like Raj said, 32mm or the standard equivalent works to turn the crank. When doing a compression test, make sure there is no fuel going to the engine. I pull the fuel pump fuse, and try to start the car before continuing on. If it doesn't start, then your good to go.

Wes

blue44

I did a compression test yesterday, 190 / 175 / 175 / 190 was the result. Still kind of hard to start and puffing a little white smoke until warm. Guess I need to check the compression specs. Still undecided about trying the head gasket...
thanks...

RajDatta

Blue some pictures of a similar job I did a few yrs back. Like I said, its not that hard.

http://www.clubstuttgart.net/attachm...1&d=1176424908
http://www.clubstuttgart.net/attachm...1&d=1176424908
http://www.clubstuttgart.net/attachm...1&d=1176424908
http://www.clubstuttgart.net/attachm...1&d=1176424908
http://www.clubstuttgart.net/attachm...1&d=1176424908

As you can see from the pictures, the head was freshened. We put new guides, new seals, pressure tested it, surfaced the head etc. The car runs very strong.
The main thing to look out for is to make sure your bearing caps are not mounted incorrectly or you don't use bearing caps from another head (shouldn't happen in your case). You would be surprised at how many 'experts' have screwed up with this and destroyed cams and heads, lol.
Good luck.

Raj

whakiewes

Raj,

I got an email of a post of yours in response to RS Barn that was deleted. I thought it was very informative and was unsure if you deleted it or if a mod did.

I agree, headgasket at home is a very possible option. A very careful person just doing a headgasket would never have to touch the cams so long as everything was timed at TDC and left there. Rebuilding the head can be performed by any knowledgable machinest. There are specific front engine Porsche specialists, but IMO unless you are looking to have serious porting/valve work done, any competent machinest can install new guides, springs/lifters, and any other non performance work you choose. Any machinest with the ability to flow bench can perform any upgrade modifications and show the gains. All of the factory timing specs are located in the service manual, so any competent machinest/mechanic with a timing wheel can reinstall the cams to factory specs (not talking about upgraded performance cams). Any upgraded cams should be supplied with timing specs so that again, any competent mechanic can install them to the specs the manufacture suggests. The head is not a 'special' head that no one can rebuild but specialists...did these specialists go to school to rebuild watercooled Porsche heads? No, they sat with a head on a flow bench and worked until they had solid gains. They don't do anything different that any machinest with tools can't do.

Wes

RajDatta

Thank you Wes!
That was my point all this point. All this CAN be done at home and the machine work is not something only a handful of people in the whole country can preform. Its not magic.
Regards.
Raj

RajDatta

Are you losing coolant? Something that you should monitor.
Raj

whakiewes

Pete,

You disagree because you are in the business to make money. The fact remains that head is nothing different than a 928 S4 head, or even any more so than other Porsche heads. Those in turn, especially the watercooled heads, are no different than any generic 16V DOHC head. To do a headgasket doesn't require port matching, 5-angle valve job, and 1mm oversized valves. It requires removing the head and reinstalling the head. I don't understand why this is so hard for you to understand. No where in a headgasket R&R does it remotely say you must time the cams, and or remove the cams. You are scewing the original point of this thread. Raj and I further the OP thread by saying now would be a good time to get some preventative maitenence done on the car, such as wear items like valve guides and lifters, and possibly a time to get a little more power. Reworking this head doesn't take a genious. Any machinest with a flow bench, as I said before, can achieve the same gains you have achieved. There is nothing different about this head other than the fact that your out of house machinest may be able to do it quicker than my machinest.

I have tinkered with my cams and head, and everything is timed to factory specs. My engine runs fine, in fact with just a chip, airbox, and exhaust, it dyno'ed 211rwhp. It took no amount of dial indicator effort to time the cams. Your MACHINESTS proprietary way of dialing in cams to .001 degree may be great for the guy who is trying to pull every last pony out of his engine, but for people like me who just wanted a head R&R its fine. Working with your cams, I can understand you have spent hours trying to dial them in, but with stock cams being off 20 degrees, I take that with a grain of salt. Mine were fine, the car runs perfectly, and it puts out a ton of power for the limited number of modifications.

The fact is that this is a job that can be done at home, by a shadetree mechanic. There are numerous guys who have, let alone S2 guys. The whole idea that a 'front engine, watercooled, Porsche trained mechanic' needs to work on this engine is garbage. Its free advertisement on a non-sponsored website. My 'rear engine, air cooled, Porsche/Penske trained mechanic of 30 years' would most definantly disagree with about 90% of what you said, as he is the one who has helped me through everything, including the 'impossible' timing of the stock cams; which took all of 15 minutes. My total bill at my machinest for cleaning, decking, valve guides, reassembly of the mechanical parts, and dealing with my BS was $310.38 for my Audi 20V head. $200 for an 8V Turbo head he did, and do I need to upload the pictures of the 928 S4 engine he rebuilt.

Not trying to provoke a pissing match, but just like you I have been there and done this as well. If you want to explain what you do differently to justify paying the middle man (RS Barn) for the work, then by all means do. But by saying its impossible to do without the right tools is blowing a lot of hot air (or typing it by this). Myself and numerous others have with relative ease. I have been in your business, and I understand what being the middle man involves, but unless you explain to the 9's, there will always be skeptics.

Wes