head studs

[sylvester]

Hello I have a question.. why do older Porsche 911 get broken head studs. and how can it be prevent thank you.

[theiceman]

oh my ....

someone could write a novel on this .. and have done so in the past .. so its all on here if you use a search function.

very short story which people will correct and expand on as people love to do that stuff..

up to 77 they don't break as much as pull out of magnesium case due to heat. 78- 83 Porsche changed the lower studs to dilivar which corrode and break and also changed the case to aluminum. They should have stopped at just making the case out of aluminum.

many people like myself put steel back in the lower 12 and it has been fine.

how to prevent it ? depends on the year of the car , but many people feel you just cant prevent it short of taking them out and replacing the lower 12 in the case of the Sc , and putting inserts in the case in earlier cars.

and don't even go there on turbos, all 24 were dilivar.

[bigel]

Nice job, Iceman...

Sly, I found five broken studs on my '87 upon removal of the lower valve covers...just finishing up replacing all the lowers with, as Iceman suggests, 12 steel lower studs. My car has been off the road for a little over two years; that's more to do with me and my free time/newbie skills than the difficulty of the job though.

I'm just about finished and just ordered a case of 20W50 in preparation for the inaugural turn of the key!

[theiceman]

Bigel funny you should say that, I just turned the key last weekend after being off the road 2 years for head stud repair ( but I squeezed in a divorce too ) ..

I was amazed it even started on 2 year old gas.

[sylvester]

OK.. got it. understood. special thanks to the iceman. and bigel.

[bigel]

Oh, this is really interesting...I was considering pumping out the 2 year old gasoline prior to startup. Maybe that's not necessary.

Originally Posted by theiceman

Bigel funny you should say that, I just turned the key last weekend after being off the road 2 years for head stud repair ( but I squeezed in a divorce too ) ..

I was amazed it even started on 2 year old gas.

[theiceman]

I had a full tank as I was shutting it down for the winter when i noticed it. So I had stabil in it.

80. Litres was a lot to dump so I went for it.

Half gone now.

[bigel]

Oh, nice...did you use any additive? I was considering filling up with fresh fuel and adding something, octane or detergent...

Originally Posted by theiceman

I had a full tank as I was shutting it down for the winter when i noticed it. So I had stabil in it.

80. Litres was a lot to dump so I went for it.

Half gone now.

[theiceman]

nope as it already had stabil in it.

I just finished the tank last night . As I have just rebuilt my engine there is no real need for addative for that, it would merely be for the fuel system , so I thought I would try a tank of fresh shell premium first after I used the old stuff up to see what happens.

When its warm it runs great , but cold starts it hunts up and down for 10-15 seconds before settling. before the 2 year hiatus it immediately started , went to 1200 , then settles to about 1000 after about 30 seconds. So I have a bit of troubleshooting to do . my base CO is sitting at about 3.0%
il whip out my CIS gauges and spare warm up regulator if things don't improve over the next tank. I hope its not my CSI , but I don't think so , I think the WUR may be gummed up.

[Pazuzu]

Originally Posted by theiceman

up to 77 they don't break as much as pull out of magnesium case due to heat. 78- 83 Porsche changed the lower studs to dilivar which corrode and break and also changed the case to aluminum. They should have stopped at just making the case out of aluminum.

A an addition, the story I've heard is that the Dilivar was coated to prevent corrosion, but it was likely that at some point, either in storage or during assembly, that the coatings got scratched, creating tiny locations where over a long time, with humidity and heat, the corrosion could start. Even if the studs were examined, it might have been when the cylinders were installed, scratching the stud in the process.


Also, remember that none of our cars were meant to go 30, 40, 50 years without being torn down a few times, if we all had a religious "reseal every 50k miles" no one would have any broken studs!

[theiceman]

Originally Posted by Pazuzu

A an addition, the story I've heard is that the Dilivar was coated to prevent corrosion, but it was likely that at some point, either in storage or during assembly, that the coatings got scratched, creating tiny locations where over a long time, with humidity and heat, the corrosion could start. Even if the studs were examined, it might have been when the cylinders were installed, scratching the stud in the process.


Also, remember that none of our cars were meant to go 30, 40, 50 years without being torn down a few times, if we all had a religious "reseal every 50k miles" no one would have any broken studs!

Mike im not sure I agree with this .

Where it is true that later studs were coated , the original ones were not at all , I do agree however that nicks and scratches will contribute to corrosion.

Even if you " reseal" every 50K miles ( which I think is crazy ) that has nothing to do with the studs, unless you are proposing the studs get replaced every 50K miles. All reseal does is replace the gaskets.

[Pazuzu]

Originally Posted by theiceman

Mike im not sure I agree with this .

Where it is true that later studs were coated , the original ones were not at all , I do agree however that nicks and scratches will contribute to corrosion.

Even if you " reseal" every 50K miles ( which I think is crazy ) that has nothing to do with the studs, unless you are proposing the studs get replaced every 50K miles. All reseal does is replace the gaskets.

We think that 50K is crazy now, because we have the pleasure of history to tell us that the engines can go 3 or 4 times that long, in general. Would a Porsche engineer suggest that in 1974? Probably not.
And a reseal is the only time you really get to do stuff like examine the whole head stud, to catch creeping corrosion. You need to get the cylinders off the block, there's no other way to examine them. So, no need to crack the block or anything, or change timing chains, but pulling the jugs off every 10 years doesn't seem that crazy to me.

My factory studs were coated, and had obvious surface damage on them after 130K miles (well ,the ones that weren't broken...)