Early_S_Man or others:
I understand the direct B-12 application for declotting a broken-off piece of carbon wedged under a valve. Do you have any advise for decarbonizing the engine generally, in part to avoid such a clot problem, and to reduce carbon-induced knock? I always heard of driving under heavy load with something like Techron as a prevention. I know it helps for valves, I am less sure about inside the combustion chamber - Thoughts?
However, on both my 2 cycle outboard boat engines (which are pretty high performance pieces of gear when you look at the power density they get from something of their low weight and displacement!) and 100cc Yamaha kart engines, you are supposed to use a serious decarbonizing solvent at the end of the season, sprayed into the intake while the engine is running. Do you or anybody else know about the wisdom of treating Porsche engines the same way?
An even wackier idea from the air-cooled two-cycle world: I was once advised to mix some two-cycle oil with the gas of my Porsche ('68 911 S) to provide for extra top end lubrication, etc. while under heavy, high rpm load, such as track use. This seems to make sense from the lube standpoint, but I am worried about its effect on both detonation/knock and carbon buildup. Any ideas?

The current owner doesn't care about cars. She owns a Porsche and that's good enough for her. There's a lot of little problems with this car to show that maintenace was not a priorty. Very doubtful the owner has a clue what the car is worth any more than the people on this bbs that haven't seen the car. Car sounds like it's condition is somewhere between fair and and average. IMO the car is overpriced without considering the potential valve job but I live on a different coast.
This is a crap shoot. This car is may need a valve job sooner than later, price it accordingly. Or pay full price and buy a piece of blue sky. Buy the nicest car you can afford.

Both this forum and rennlists seem to tell me you like this car. It sounds nice and I guess you would buy it if it were not for the leakdown.
The thing is, whenever this lady wants to sell the car she will be confronted with people like yourself getting PPI's done, and she will get the same results each time. No idiot buys a 911 without one (sorry to the people who didn't and have had good luck).
So it should be in HER best interests to sort this problem out.
Luckily, because of the magnificent advise on this Pelican BBS you are now aware of the carbon fouling problem on underdriven cars and can point this out to her. Whilst it pays to be suspicious of mechanical problems in these cars you needn't always assume the worse!

It doesn't sound to me like a difficult soloution:

You place a deposit on the car with a carefully worded and signed receipt saying that you are willing to purchase it for XX IF the problem is carbon. You then tell HER to buy a few bottles of Techron and get a wrench to perform Warren's cleansing ritual (Remember, it will be in her best interests to do this if she actually wants to sell the car).
Then you get another leak down test done ..at her expense, or negotiated out of the original price. If it's all clear, buy. If it 'fails', then take your deposit back and keep huntin'!!!
Easy, and works for all parties. Motto: less worry, more soloutions.

Sorry Warren, I should have read your post more carefully. I was under the impression that you were recommending the "typical" pop in techron and run the crap out of the car. I didn't realize that your method was a quick fix. Like I said before, I'm new to this stuff. When you said "let engine sit overnight, and repeat treatment again", I thought the "treatment" you were talking about was actually going out and driving the car hard. I will have a Porsche mechanic look at your solution and I will have him do it!

And no, I probably can't do a compression test with a gauge that requires me to remove all the spark plugs and etc...not yet anyways. But I watched the mechanic do it and he was nice enough to tell me exactly what he was doing the whole time. One of the reasons I'm getting a car like this is to snag myself one of those Bentley manuals and learn, learn, learn (or read, read, read). I don't know squat right now, but I plan to learn and tinker around. But again, I apologize for sounding repetitive, especially when you had a quick procedure right there.

DTW - sorry, I think she's taken.

Don - exactly correct, I think the car is somewhere between fair and average. I read that long thread concerning Bruce A's pricing description, and this car is definitely under "good". In all fairness, the car was properly maintained by the 1st owner up until April 2000 (about 19-20 months). The only reason the current owner is pricing the car at around $14.5k is because she paid $15k for it last April. She said she was very flexible with the price.

Matt - thanks for the tip. The car would be in my garage right now if it had passed the PPI with flying colors yesterday. One of my friends gave me this scenario (he's an investment banker, and he likes to jump on any opportunity)...I think it's kind of unfair:

1) Inform her of the leakdown problem and the cost of a valve job ($3.5k).

2) Negotiate the price down to about $10k for the car. Tell her that other people will have a PPI performed, and they will also see that #6 red flag. Inform her that a resolution is absolutely necessary, and I am willing to take her "problem" for a reduced price.

3) Buy the car for the reduced price. After purchasing the car, do the various fixes mentioned in this thread concerning the carbon problem.

4) If it is indeed a carbon problem, wow, you just scored a decent 1983 911 SC for $10k.

5) If it is more serious and requires a valve job, too bad, add $3.5k to the purchase price, and you're in the same spot where you originally were (looking for a decent 911SC for around $14-15k).

So my buddy is proposing that I simply tell her the scenario, don't offer any tips or advice for her to actually test out the #6 cylinder, buy the car for a reduced price, and gamble that the car just had a carbon problem. After all, he said, the car's only major problem is the #6 cylinder; everything else checked out satisfactory during the PPI. Again, this is his idea. I'm not sure. I understand what he's trying to say, but it's like I'm taking advantage of some poor Porsche owner who doesn't know much about these cars. In addition, who's to say that a valve job would completely solve this problem, and who's to say that this engine is just a ticking time bomb?

Hopkinskid

Pleez, forget this attitude that you are taking advantage of a poor defenseless female Porsche owner. You are buying a used car that can quickly become very, very, expensive to repair.
Follow your investment banker friends advice.

I'd be somewhere in the middle of your banker buddy and the owners original offer...IF you like THAT car!

Lowballing her , she is bound to say forget it..and if the car runs good compression after berrymans, you wont feel like a banker... errr uhhh crook! :)

Good luck.. and have fun!

Don - I guess I kinda feel guilty. The owner went out of her way to show me everything wrong with the car, no matter how small. So I guess I'll feel a twinge of guilt if I don't tell her about the possible carbon issue. I guess that's why I wasn't cut out to be a banker/analyst (quit after 9 month).

Reg - I truly like the car. It has some work that needs to be done, but I've spent about 5 hours looking through every nook and cranny, and 2 hours driving the thing. The PPI was satisfactory, of course, except for #6.

I am going to offer somewhere in the proximity of 10.5k and 11.0k. I would have purchased the car for $13k-$13.5k if the compression/leakdown numbers had come out ok. Unfortunately, #6 did not. So what do you guys think? Is $10.5-$11.0k a fair price for this car? After trying the carbon build-up "fixes", I could end up paying $10.5-$11.0k for a nice 1983 SC, if the compression/leakdown numbers improve. If not, oh well, I'll just have to tack on the cost of a valve job ($3.5k) in the next 1-3 years, and suck it up. Maybe in 2 years, I'll have enough experience to do the job myself (ha ha, yeah right). Remember, I live in the Bay Area, and this car is 30 minutes away. I realize that the "original" $13.5k price may be high for a 1983 911 SC with 116k miles, and I know I can find a similar car out of state. So I could try to find a car with the similar specs, updates and condition elsewhere in the US, but I think I would rather pay $1-$1.5k extra for the car, as opposed to shipping costs, long-distance PPI costs, possible air ticket, etc. Again, I would estimate this car to be slightly under "good" condition, if you look at Bruce A's description. I would probably have to spend $1-$1.5k to get the exterior and interior straightened out completely. And besides #6, the car is in decent condition.

So $10.5-$11k due to the problem with #6 and possible valve job in the future. Any opinions?

Thanks,
Hopkinskid

H: A lot of good things come from buying a car locally - you will be glad to avoid the hassle and additional uncertainty of buying a car long distance. Besides, I'm betting the Bay Area tech crash hasn't help Porsche prices. Since you have bought this car in your mind already, go for it! Remember however, that no matter how much you try to plan ahead for predicable expenses, there are always the unexpected ones (alternator, starter failure, etc.). So try not to spend your allocated maintenance budget on that possible valve job thinking that you will then be set. Better put that $3.5k in the bank and leave it there if you get any compression back on #6, or even if you don't but the car runs nicely, because you will certainly need it for something else down the road (I'm not trying to be pessimistic, it is just part of the deal of owning a 20 year old car that it requires regular and on going maintenance inputs. As you said you aren't a do-it yourselfer, it can really add up. I recommend you approach every maintenance item recommended by your mechanic with the same sober and careful evaluation of whether it is truly needed. Very few maintenance items on these cars are so critical that putting them off, or trying them yourself and failing will make the thing blow up). Good luck!

Buy the car already!

:D

hopkinskid,

I don't know if you have read about the history of Dilivar head studs and recent corrosion and cracking/breakage 'issues' that have come to light in the past six/seven years or so for SC's and Carrera's, but it appears to me that the cause for the valve job in 1996 had nothing to do with ownership by women!

Since you have access to the paperwork, ONE thing that needs to be determined is whether of not the studs that were installed in that engine when the valve job was done in 1996 were another set of Dilivar's or OEM steel like the top row. If they are Dilivar in there NOW, then there is another check that probably should be done ... and that is to see if all 24 10 mm Allen (barrel) nuts are tight. Cracked or broken head studs may be a factor in the leakage in cylinder #6. You may be able to contact the shop that did the work to see if they were replacing broken Dilivar head studs with steel OEM studs in 1996.

The answer as to how much future trouble to expect from that engine may rest upon which kind of studs were installed in 1996. I don't believe the 'quality' of the work would have taken five years to become an 'issue!' The Dilivar studs are a concern now, and are not something that I recommend that people leave in their engines ... waiting for them to fail, like a ticking 'time bomb!'

Reading Warren's post about the Dilivar studs and the light went on.
It's a good chance that the one cylinder problem doesn't have anything to do with carbon. It could be something as simple as the heads have never been retorqued. It just seems too much of a coincidence that only one cylinder has a problem and you can hear air escaping from the intake and exhaust.
Concerning the Dilivar studs, who knows what was used. When the top end was rebuilt Carrera tensions were also installed. Sounds like the PO that had the work done was trying to take care of potential problems and may have used Raceware or something else.
Even if Dilivar studs were used they're still in better shape because of age than the originals. Wouldn't let whatever studs installed be the deciding factor.

Warren - I thank you for taking the time to help me with this car. I took your advice and I contacted the shop which did the head stud replacement back in 1996. They told me that they used Dilivar turbo (?) studs, and they were made of different material than the dilivar studs which were problematic. Any comments? Are there different "types" of Dilivar studs back in 1996?

I am also having my mechanic try your declotting procedure this week on the car.

Don - thanks again for your reply. I actually printed out this whole thread and I showed it to my mechanic. He commented that he may be losing business and out of work soon!

Thanks again.

John Walker spoke of some powder coated Dilivar studs introduced sometime at the end of SC production; could this be what your tech. is referring to?

Clueless,
John

Yes ... there were at least three different Dilivar stud versions used in production engines, and two more for racing engines.

I have never heard of a breakdown of Dilivar failures by type, and Bruce Anderson does not recommend thay any of them be used any longer if you have an engine apart! There have been cases of them breaking only minutes after being torqued in a fresh engine assembly ... called the 'flying Dilivar ' phenomenon, the broken stud and Allen nut are said to depart the engine at high velocity and bounce off shop walls! So far as I know, no explanation has ever been offered as to why brand new Dilivars break!

Since you have contacted the shop and gotten straight answers from them, ask them if the black epoxy-coated ones were used, and if THEY are aware of any problems with that version of Dilivar stud.