1983 911sc stud question

[robert walsh]

i have 1 1983 911sc, i thought by 1983 the 911sc 3.0 was more or less over the stud failure problems prone to earlier models. i know now and again it can come up but for the most part i thought it was pretty much corrected. what years did it affect the most? and what year, for the most part, was it resolved. thanks bob

[Superman]

It's a roll of the dice. You have no reason to be over-confident. My '83 SC broke a head stud. The Dilivar studs were used at that time and they can corrode and snap. Count head stud nuts from time to time. When they break, they will likely fall off.

[jonbot]

Will a magnet help you differentiate whether or not your studs are steel as opposed to Dilivar?

[dtw]

No, the Dilivar studs were still in use. I just popped the covers on an original/untouched '83 SC motor with 7 broken studs this year.

Further, Carrera motors are now starting to exhibit stud failures.

[Bill Verburg]

I've seen broken head studs all the way up thru the 964 models

[robert walsh]

Thanks For All The Responses, Are There Any Symptons That I Would Notice If There Was A Broken Stud Or Two, It Seems Like At This Point Is Not Preventitive At Least From A Financial Point Of View, As It Was When I Upgraded Too Hydrolic Tensioners Which Cost Me $2200.00 Back In 1994, Genunine Porsche Parts And "genuine German Labor" Also. Are There Any Sibns That Would Lead Me To Think I May Have Any Broken Studs? It's Running Great With No Oil Consumption At This Time. Thanks Again

[ramonesfreak]

if you do a search on the forum you will find many threads on this topic. i believe its possible to have no noticeable symptoms at all. or you might hear an ehxaust leak sound upon exceleration. you may find a broken stud when you remove a valve cover. have you crawled under to look at your cylinders? do they look clean?

im hoping not to find any broken when i do my first valve adjustment soon. im dreading this....but, the engine runs perfectly so im hoping all is well...for now

[gtihop]

I had 3 broken studs on one side on my 83 sc with 75k on it. no noticable problems that indicated they were broken and probably had been for a long time as the tops of the studs were not there. probably taken out by the PO .

[Peter Zimmermann]

I've been working on a new book (title & publication date still unknown!), and I realized that one of the chapters fit this thread and might possibly provide some insight to head studs. Please consider that this information does not come from Porsche, it comes largely from my personal experience in the trenches working daily on 911 automobiles. I have done everything possible, using personal notes, etc., to insure accuracy, but the history of some things that Porsche has done can be considered murky at best. This chapter is not written in stone, and I'm open to knowledgeable discussion regarding its content. What you're going to read should be considered copyrighted material, so it may not be used or...blah, blah, blah. Enjoy!

Cylinder Head Studs

1977. Porsche was well aware of the problems associated with the 2.7 liter engine with its pulled cylinder head retaining studs following a repair that required cylinder head removal; sometimes the studs would pull without apparent reason. Porsche knew about thermal expansion, and had used, since the early ‘70s, in racing engines, a cylinder head stud made from an alloy called dilavar, while all street engines were assembled with steel head studs. Dilavar studs, first used in 930 Turbo Carrera engines, were found to have roughly the same thermal expansion properties as both aluminum and magnesium, which, in theory, would greatly reduce head stud stress at higher engine temperatures. It’s been written that steel studs, on the other hand, have an expansion rate roughly half that of the aluminum cylinders and cylinder heads that they hold together, which placed extreme loads on the crankcase and the studs themselves. Dilavar studs, a non-magnetic steel alloy, found their way into 911S production part way into the ’77 year, and the studs were only used in the bottom twelve, exhaust side, positions (each 911 engine uses 24 studs, 4 per cylinder head). A thoroughly tested no-brainer, or an experiment, I don’t think that anyone knows the answer to that except for a select few people at Porsche. The first dilavar studs were a shiny, brushed finish, similar to many modern kitchen cabinet and drawer pulls, with a color closer to silver than to light gold. Their purpose was to stabilize cylinder head torque through the temperature range that the typical 911 engine ran at. I’m sure that the factory hoped that Dilavar studs would also be the cure for pulled head studs in magnesium engine cases. Because the thermal expansion rate between early steel studs, and the alloys that they secured, was quite different, the change was made.

1980. The first improvement to dilavar studs was made for 1980 SCs, which proved that Porsche was committed to their use. The stud changed in appearance, to an almost jewelry gold finish. For this design change to happen so early into the use of dilavar, Porsche must have seen, and not liked, corrosive activity on the first generation stud. Factory literature states that Porsche’s original philosophy of using twelve upper studs made of conventional steel, and twelve lower studs made of dilavar, remained consistent beyond the 1980 models. At some point dilavar studs were again changed, and the newer version was coated with a gloss-black paint-like substance obviously designed to withstand corrosion. This change was thought to have been made during 1981 production, or at the outset of the 1982 build run.

OK, you’ve read the first part of this chapter and are probably wondering why. Well, if you own a ’77-81 SC the subject matter above could easily make you about $3K+ poorer. Head studs break. Some more often than others, but mostly the problem occurs with the uncoated, early studs, followed by the second generation, also uncoated, studs. The studs break about two inches from the end where the head nut screws on; they are obviously susceptible to corrosion at that point. A fastener such as a stud, or bolt, is under constant stress, from the time that it is tightened until the time that it’s loosened. The act of applying torque to a fastener is the actual stretching of, in this case, the stud. Enter corrosion, which attacks where it can, and begins to eat away at the metal. Remember, dilavar is a steel alloy, it is not immune to corrosion, actually far from it. At some point in its life, a corroded head stud will snap at its weakest point, and will no longer provide the fastened strength that a cylinder head requires at each of four corners.
Head studs break on low mileage cars; perhaps more often than on high mileage cars. “How can that be?” one might ask. No one knows the answer, but I know it to be true. I also know that it doesn’t happen to all cars, maybe even less than ten percent of each involved year. My shop replaced head studs on far more cars with less than 50K miles on the odometer, than with more than 100K miles. It can create a bit of a conundrum; the cars that can be considered garage queens, and are obviously the most desirable to find and buy, are the ones that have this potentially expensive time bomb lurking in the engine bay.

FAQs:
“How does one know when a head stud is broken?” All 911s built between 1977 and 1989 have the same maintenance requirement for what is normally referred to as a major service – typically required at about 15,000 miles. That service consists of a valve adjustment, oil and filter change, engine tune up and other items. In order to perform a valve adjustment, the valve covers, aka rocker covers or rocker arm covers, must be removed. There are four covers per engine, and are usually referred to as intake (upper) covers and exhaust (lower) covers. During removal of the lower covers I have been hit on the foot by a two inch long piece of a head stud, with the cylinder head retaining nut still on it. Sometimes the broken piece will fall out; sometimes it will hide in a recess in the camshaft housing casting. A normal major service inspection should include, especially on high-risk cars, a visual to verify that all of the studs/nuts are intact.

“What is the immediate symptom?” Usually there is no symptom, especially on conservatively used, commuter or weekend cars. I’m aware of cars that have been driven thousands of miles after a broken head stud was diagnosed, with no negative result.

“When does stud replacement become something more expensive?” If one or more broken studs are discovered during a major service and the needed repair is ignored, at some point a corner of a cylinder head, usually the corner with the broken stud, will work loose enough to leak combustion (the gases that are supposed to leave the combustion chamber via the exhaust valve). From the very moment exhaust gases begin to leak out between the cylinder and cylinder head the process of erosion begins. Eventually a cylinder, possibly even a cylinder head, will be damaged beyond repair.

“Is there a symptom when it’s almost too late to do the basic stud replacement without extra cost?” Yes, the driver will hear a distinct and rapid “pop, pop, pop…” during acceleration; louder with a cold engine than a warm engine.

“Is there any way to ascertain the presence of a broken stud without hearing the popping noise, or removing the valve covers?” With the car raised up enough to see the bottom of the engine, a flashlight examination can be done of the areas where the cylinders and cylinder heads join. Those areas should be dry and clean. If there is a black, crusty layer that appears to be burned oil, there is a chance that the engine has one or more broken head studs where the buildup is the heaviest. However, a broken head stud is not always responsible for this condition, sometimes it is from a tiny imperfection in a machined surface, and no immediate repair is required.

“If my engine has broken studs can the job be done so the repaired engine is a long-life unit?” Going by everything that is known today, the current generation of cylinder head studs, developed for the 993, should be trouble free for at least the service life of the engine that they’re in.

“If my engine was originally fitted with steel upper studs, and Dilavar lower studs, should all 24 studs be updated to Dilavar?” Porsche must have done temperature analysis regarding the required expansion of the upper and lower studs, but I’ve not seen a technical bulletin advising the correct way to handle this. My shop found evidence of corrosion on original, steel upper studs, so our policy was to install 24 new dilavar studs on those engines (the exception being engines that we repaired on which the upper steel studs were visually perfect). Follow up inspections showed no adverse results, including unusual loosening of head nuts which would require periodic re-torquing, regarding those repairs.

“Are the black-coated generation of studs, used since late 1981, the latest generation Dilavar?” No, Porsche developed a new Dilavar stud for 993 models (1995-1998), and 993 studs should be used for all repairs.

“Can anyone do this repair?” Usually you’re better off with a seasoned professional when 911 engine repairs are needed. There are an assortment of special tools needed to perform stud replacement, and it always helps for your technician to have a set of factory repair manuals on hand as well. There is no really good answer for this question, because there are probably DIYers out there who are more competent than the available mechanic. My advice is to do your homework, ask every question that you can think of, get referrals, and then check out the shop you’re thinking of using. When you get there and you don’t see anything but a clapped-out 924 and a bunch of 3-series BMWs, rethink your choice.

I hope that this post has answered some of your questions!

[ramonesfreak]

nice write up.

all my cylinders are slightly blackened where they meet the cylinder head..not sure if its from old oil dripps from leaky valve covers or studs or as you explained - metal imperfections...ill find out when i take the covers off i guess

http://forums.pelicanparts.com/porsche-911-technical-forum/418454-oil-dripping-near-3-cylinder.html#post4049202

[robert walsh]

A quick follow up question then, if i have an oil leak (fresh oil) comming from the head area of cylinder #1, it is probably not a stud issues, seeing that it is not burnt oil by means, should i feel confident now that i am looking for a hopefully less esxpensive oil leak? There is no popping on acceleration nor burnt oil deposits that i can see and believe me i have looked. Thanks foe everyones help, and peter good luck with the book.

[ramonesfreak]

you should be more specific regarding where the oil is coming from or take a pic. it could be the valve cover gasket or oil dripping from a higher spot.

as the article says, and most mentions of head studs say, you can rule out head studs being broken almost always by taking the valve cover off.

if you take it off, and find no broken studs, and also put a fresh gasket and new washers on, you may eliminate two problems (worries) right there......

[1982911SCTarga]

Peter, do you have any theories regarding the low-mileage stud-breaking issue? Could it be attributed to a greater propensity for stud corrosion because the low-mileage cars tend to be short-hop driven? Thanks for the information!

Brian

[Peter Zimmermann]

Originally Posted by 1982911SCTarga

Peter, do you have any theories regarding the low-mileage stud-breaking issue? Could it be attributed to a greater propensity for stud corrosion because the low-mileage cars tend to be short-hop driven?Brian

Brian: I've thought about this until it made my brain hurt! I think that you've got it pegged, and I also know of a few cases where the low mileage car was started periodically in the garage, left to idle for a short period and shut off without being driven. The resulting temperature change can be a true breeding ground for moisture/corrosion.

Robert W.: Without a photo, I'll bet that your leaking oil is also running down the forward side of the chain housing before it drips on the floor - let me know if that's the case...

[robert walsh]

Peter, since your on now and i am at work unable to photo, if you had to diagnose with info available would you think stud issue or other problem, give that it is solely located at cylinder #1 and it is fresh oil, about a dime size or less after a vigorous outing, i don't think its stud related, it just runs way too good and it has been there for several years, i dont put that many miles on, 3k since last valve adjustment, i had a lackluster mechanic plant the stud seed in my brain, said he didn't have the time to diagnose the leak, i will change the valve cover gasket and find out for surre, i am very interested in your opinion. thanks

[Peter Zimmermann]

Originally Posted by robert walsh

Peter, since your on now and i am at work unable to photo, if you had to diagnose with info available would you think stud issue or other problem, give that it is solely located at cylinder #1 and it is fresh oil, about a dime size or less after a vigorous outing, i don't think its stud related, it just runs way too good and it has been there for several years, i dont put that many miles on, 3k since last valve adjustment, i had a lackluster mechanic plant the stud seed in my brain, said he didn't have the time to diagnose the leak, i will change the valve cover gasket and find out for surre, i am very interested in your opinion. thanks

If I had to take a guess I would say that your left side camshaft o-ring is leaking. The o-ring fits on a circular aluminum plate that secures the chain housing to the camshaft housing at the rear end of the cam. The classic symptom is that the oil leaks past the o-ring, runs down along the forward (driving direction) side of the chain case and drips off the lowest point of the chain case - usually after a drive when the car has reached full oil temp. This leak only occurs while the engine is running, and usually will only drip for a few minutes after engine shut down. If I'm right you should be able to see a clean "path" where the oil has washed the chain case between the head/cam housing and where it drips onto the floor. To check this you have to raise up the car high enough to get your head under the left side cylinder area and look up at the side of the chain case that faces toward the front of the car (use proper safety equipment to secure the car before you go under it!!!).

[jwasbury]

On my Ducati motorcycle. I think my Porsche is ok, but I will check carefully again the next time I have the valve covers off.

I have a 1995 Ducati M-900. The Ducati of that era were supposedly breaking studs a lot...there were many warranty repairs from what I understand. I had my bike for 12 years before it broke a stud (2 years I raced it in AMA club racing events). A respected Ducati wrench has the theory that if the bike is ridden hard (high revs, no lugging of the engine at low rpm, high load situations) was less prone to stud breakage because the engine is much smoother at high rpms (and shakes like crazy at low RPMS).

Could the reason be similar for the low-mile garage queen 911s? Maybe the low mile cars are more often babied and short shifted, and this is actually harder on the studs than running it to redline?

[robert walsh]

Well i guess you didn't think this was comming huh? As best i can tell you nailed it, it seems it is running down the chain housing, only when driven, nothing when car is not running, now what am i looking at to get the cam oring replaced, estimate dollar wise approx?? Will i do damage or cause further damage or perhaps cause the dredded casastrophic engine failure, seems i dodge a bullet only to look behind and find another hunting me down. The car reallly doesn't use any oil, 750 miles since oil change and has not moved a bit on the dip stick, i've only owned it a few month and the PO new little about the car, tlaked to the previous owner of most of it's life and he gave me the green light on the purchase and years of repair and maintainance reciepts. Purchased without a PPI because i had to have it, it's the only one that i couldn't let get away. I wanted 83 911sc coupe w/sunroof, drove the cab with the top down and drove it home. Platinum metallic, cork interior, black top. Would post some pic's but i honestly don't know how to. Thanks again p.s. sorry about the spelling, also i owned a 59 cab in the early seventies, i guess i never lost that feeling! I could go on forever i love this stuff, i'll shutup now

[Peter Zimmermann]

Originally Posted by robert walsh

Well i guess you didn't think this was comming huh? As best i can tell you nailed it, it seems it is running down the chain housing, only when driven, nothing when car is not running, now what am i looking at to get the cam oring replaced, estimate dollar wise approx?? Will i do damage or cause further damage or perhaps cause the dredded casastrophic engine failure

Nah, it's just irritating. But, there was never a better time to update the engine to Carrera Tensioners (if they haven't been done yet). When you plan on having it fixed choose your mechanic wisely, set aside the funds to have both sides done, and have all six chain guides replaced while you're in there. This is not a difficult job for a highly experienced technician, but you want a good guy because both cams have to be re-timed - and you want that wonderful car to run as well after the repair as it does now. Call around for some estimates, but be aware that the job is done with the engine in the car - there is no need to pay for R&I. I think that about 10 hours is a fair charge for labor (the center engine mount pylon has to be removed to replace the right side chain guides, aka ramps). Of course, if exhaust hardware is rusty factor in a little extra time for removal. Good luck with it!

[robert walsh]

The hydrolic cam tensioners have been done, i have the reciept for $2200.00 from a porsche delaer in greewich ct. i believe, so at least that has been done, from the detailed listing of bits and parts replace at that time it seems to be a very thourough job. thanks