Dreaded Broken Head Stud...

[awjens]

Was getting ready to clean up the SC and was changing oil, brakes, adjusting valves as car hasn't been driven much since 1998. (Less than 5k miles since Paul Wier Rebuild). Took valve covers of only to find a large hardened washer...then a short piece of Dilavar stud.

When Paul did this (rest his soul) he asked me about the Dilavar studs. He mentioned they can be problematic. I asked him Porsches recommendation and they were still pushing Dilavar. He wanted to use steel. I insisted Dilavar..... my bad.

So now its out, and I decided to replace all the studs. Also had a 9% leak down in #5 all the rest were 3-4%. Sent the heads to Mark at Exotech and all new guides/seals etc. Only #5 was sticking a bit. But with it this far apart no sense sending in a single head.

So now all the parts are back, exhaust ceramic coated, engine tin powder painted, crossmember, engine mount. All new injector bushings, orings, hoses, oil lines etc.

Found a section in Waynes book about oil line restrictors, decided to order them...still waiting.

With everything new up top and less that 5k on the bottom, anything else worth doing while its this far?

It got JE Pistons, new oil pump, tensioner update, Mahle cylinders. All new bearings, rod bolts. New chains and gears, chain guides.

[Reiver]

Looks nice and clean.
How long/miles did that rebuild with the dilivar last you?

[pmax]

Originally Posted by Reiver

Looks nice and clean.
How long/miles did that rebuild with the dilivar last you?

OP said 5K since 1998. I read somewhere that cars not driven much are more likely to suffer from broken studs.

[Reiver]

Originally Posted by pmax

OP said 5K since 1998. I read somewhere that cars not driven much are more likely to suffer from broken studs.

That's what the professional wrenches tell me because often that equated to short drives that never allowed the engine to get to proper temp.
If the dilivar was compromised then the engine sweat would attack the area.
Shame.

[chris_seven]

Was the stud one of the latest type of fully threaded Porsche Studs?

I have to say that from a metallurgical perspective there is no logic to the concept that engines that are rarely driven should have more problems with a Dilavar stud.

Dilavar is not an alloy which would corrode in the presence of condensed water as it is fundamentally an Austenitic Stainless Steel.

The corrosion of grain boundaries in the presence of chlorides is the only issue that is likely to be a problem and cars that are not driven on salty roads are unlikely to be affected.

There are also the reported failures due to hydrogen embrittlement which can only occur due to bad manufacturing practices.

This type of failure will probably be stochastic in nature and very difficult to predict on an individual basis

I still believe that there are studs being sold as Dilavar and these should be avoided like the plague.

The 'Magnetic' Dilavar studs being offered being as case in point as the metallurgy of these studs is at best confused.

I just bought new steel studs form Porsch and paid $6.50 each which is a great price.

[JRSIII]

Where did you send your exhaust to have it coated? What type of ceramic coating is that?

[Discseven]

Something mystical to cleaned parts. Looking good Awjens ~

[gomezoneill]

With everything new up top and less that 5k on the bottom, anything else worth doing while its this far?

When you install the rocker shafts torque them to 21 ft lbs. This will keep them from leaking and they'll never back out. Also steel studs are fine unless you plan on building a high compression racing engine then I would use ARP.

[betterair]

are you installing the cam oil seals?. Cheap insurance to insure against cam tower leaks.

[awjens]

Originally Posted by chris_seven

Was the stud one of the latest type of fully threaded Porsche Studs?

I have to say that from a metallurgical perspective there is no logic to the concept that engines that are rarely driven should have more problems with a Dilavar stud.

Dilavar is not an alloy which would corrode in the presence of condensed water as it is fundamentally an Austenitic Stainless Steel.

The corrosion of grain boundaries in the presence of chlorides is the only issue that is likely to be a problem and cars that are not driven on salty roads are unlikely to be affected.

There are also the reported failures due to hydrogen embrittlement which can only occur due to bad manufacturing practices.

This type of failure will probably be stochastic in nature and very difficult to predict on an individual basis

I still believe that there are studs being sold as Dilavar and these should be avoided like the plague.

The 'Magnetic' Dilavar studs being offered being as case in point as the metallurgy of these studs is at best confused.

I just bought new steel studs form Porsch and paid $6.50 each which is a great price.

These studs were purchased in 1998. There wasn't any corrosion on them to speak of. Very disappointing to spend that money, rarely drive it and find that doing routine maintenance. There are wild temp swings here, last couple winters saw temps in double digit negatives. This car was inside the garage the entire time, so it probably saw 35-40 degrees at the lowest. I never started it when it was that cold. So it would go a couple months without a start. This car has never seen a salty road. I replaced them all with a good set from our host. I just wish I had followed Pauls advice. I am selling this car and I refused to sell it with a broken stud. Especially since spending almost 10k in 1998 an driving it for 5k miles. At least I know now everything he charged me for was done..... The sticky valve in #5 probably would have went away on its own, I only ran it for 20 minutes and drove it for 1/4 mile before pulling it into the shop for the "maintenance". I don't cut corners so hopefully its new owner gets tens of thousands of miles of trouble free driving.

[awjens]

Originally Posted by gomezoneill

With everything new up top and less that 5k on the bottom, anything else worth doing while its this far?

When you install the rocker shafts torque them to 21 ft lbs. This will keep them from leaking and they'll never back out. Also steel studs are fine unless you plan on building a high compression racing engine then I would use ARP.

I bought a new wrench just for the rockers, I'm also installing RSR rocker shaft seals. This is s stock 3.0 euro so I went with steel. On my supercharged car I used raceware studs/bolts and ARP rod bolts.

[awjens]

Originally Posted by betterair

are you installing the cam oil seals?. Cheap insurance to insure against cam tower leaks.

What seals are you referring to? I bought a complete engine gasket set, and RSR rocker shaft seals. Is there something else I can add to help prevent leaks?

[awjens]

Originally Posted by JRSIII

Where did you send your exhaust to have it coated? What type of ceramic coating is that?

I sent it to a die hard racer in Saginaw MI. Its ceramic coating, a three or four step process that includes a base coat that is corrosion protection. He had a shop full of high dollar exhaust manifolds and pipes. 450.00 for everything, from head to tailpipe.

Component Coating

2550 California Ave

Saginaw MI 48610

(989) 746-0891

[awjens]

Originally Posted by chris_seven

Was the stud one of the latest type of fully threaded Porsche Studs?

I have to say that from a metallurgical perspective there is no logic to the concept that engines that are rarely driven should have more problems with a Dilavar stud.

Dilavar is not an alloy which would corrode in the presence of condensed water as it is fundamentally an Austenitic Stainless Steel.

The corrosion of grain boundaries in the presence of chlorides is the only issue that is likely to be a problem and cars that are not driven on salty roads are unlikely to be affected.

There are also the reported failures due to hydrogen embrittlement which can only occur due to bad manufacturing practices.

This type of failure will probably be stochastic in nature and very difficult to predict on an individual basis

I still believe that there are studs being sold as Dilavar and these should be avoided like the plague.

The 'Magnetic' Dilavar studs being offered being as case in point as the metallurgy of these studs is at best confused.

I just bought new steel studs form Porsch and paid $6.50 each which is a great price.

Here's a picture of the one that was adjacent to it. This one and the broken one were on #2. That cylinder had excellent compression and a 3% leakdown.

[911pcars]

Originally Posted by awjens

Here's a picture of the one that was adjacent to it. This one and the broken one were on #2. That cylinder had excellent compression and a 3% leakdown.

Looks like one of the earlier versions of Dilavar. 4-5 factory versions were offered, not including knockoffs. Were they yellow zinc plated or all plain? Since then, the factory had black coated as well as the latest full-threaded versions.

Sherwood

[Reiver]

Originally Posted by chris_seven

Was the stud one of the latest type of fully threaded Porsche Studs?

I have to say that from a metallurgical perspective there is no logic to the concept that engines that are rarely driven should have more problems with a Dilavar stud.

Dilavar is not an alloy which would corrode in the presence of condensed water as it is fundamentally an Austenitic Stainless Steel.

The corrosion of grain boundaries in the presence of chlorides is the only issue that is likely to be a problem and cars that are not driven on salty roads are unlikely to be affected.

There are also the reported failures due to hydrogen embrittlement which can only occur due to bad manufacturing practices.

This type of failure will probably be stochastic in nature and very difficult to predict on an individual basis

I still believe that there are studs being sold as Dilavar and these should be avoided like the plague.

The 'Magnetic' Dilavar studs being offered being as case in point as the metallurgy of these studs is at best confused.

I just bought new steel studs form Porsch and paid $6.50 each which is a great price.

Chris,
I believe your explanation but I've heard this from numerous wrenches about the low mileage head stud issue.
One, who I know well (been doing 911's since the late 70's) says he finds many more low mileage Dilivar issues than high.
Obviously not the sweating issue but must be some correlation.

[DanielDudley]

Because the bad one break early. The good ones last.

[awjens]

Originally Posted by Reiver

That's what the professional wrenches tell me because often that equated to short drives that never allowed the engine to get to proper temp.
If the dilivar was compromised then the engine sweat would attack the area.
Shame.

I didn't drive it often, but the office was 45 miles each way. Trips were 45 miles minimum. A few to the cabin and back >120 miles each way. It was never used for local driving or a trip to the store. Had I taken Paul's suggestion, I wouldn't be in here now. It ran great. These were factory Porsche Parts. I ordered them.i don't know why it would fail, but it does seem that a lot of them break on cares that are rarely driven.

[Reiver]

Originally Posted by DanielDudley

Because the bad one break early. The good ones last.

That is a possibility but you'd have universal statistics if that were the case.
Every P site I've visited that discussed this subject noted the same occurrence....more studs breaking on garage queens than high mileage cars.
It would be interesting to find out why.

[prschmn]

Hey Art, Glad you're happy with the heads. A favor though?
Been a week and a half but the money hasn't shown up in my Paypal?