Should I replace the head studs?
 

My SC's engine is still apart, waiting for the cylinder heads to return from the engineering shop with new valve guides.

With the engine block on the bench, I took a magnet to the head studs. The intake rows were predictably magnetic, being steel, but the exhaust rows were not. Closer inspection revealed a colour difference from the upper row of steel studs. My mechanic was certain that all the studs were steel, until I did the magnet test.

Question: Should I now replace the dilivar studs with steel studs, given that they have lasted 27 years already? I could not see rust anywhere on them, but everything I have read says replace them. There is the risk of snapping the studs while attempting removal, but to me, this is a smaller risk than putting the engine back together and snapping a stud a few weeks/months down the line. I'm therefore leaning towards replacement.

Opinions?

LeRoux

I'd replace them. They seem to be more likely to fail soon after being disturbed.
-Chris

Several people have said not to re-use Dilivar studs. There's a guy on this board who re-used his dilivars on his 2.7 and within several hundred miles one broke and he had to tear down the motor part way and remove the stud! REPLACE, and get steel instead.

Without a doubt - replace with steel while you have the opportunity.

I'd replace them w/ 993 versions

My opinion: replace with steel like the uppers.

Assuming you have the cylinders removed also, use a torch inside the case and pour some heat to it (it will take awhile as you are heat a large heat sink). Once the case area surrounding the stud gets hot, the studs will back out with very little torque required. I just did the same to my '79 SC (one of the dilivars cracked when the heads were removed).
If you do not use heat, you run the risk of breaking a stud off at the base and then you are in for some real fun.

Definitely replace!

see my poll on head studs..if it was my motor, alreadsy apart I would replace

You don't have to replace the dilavar studs now, you can do it in six months when one breaks ;)

Just being a smart a$$, yes you should definately replace the lower studs with steel. I used the 993 steel studs, relatively cheeep and work just fine.

Bill, why do you say the 993 versions? Just curious, as my SC had the 993 versions installed a few years ago after one broke.

Give the divs the float test....go steel 993s like Sammy said...

Are the 993s steel?

Do you have the p/c removed? If not, that makes it an interesting question. Because you have to remove p/c to get to the studs. Unless you leave the pistons in the cylinders when you remove them, you are opening another can of worms. What if your pistons are worn, what if your cylinders are out of spec. What if you mess up and break a ring?
It can become a very slippery slope. Once the cylinders are off, you can then replace bearings on the crank and why not split the case while you are at it ... yada yada .... 5k later and you'll be SURE that nothing will every go wrong. :D

I am not saying that you should take any shortcuts, but weigh carefully how deep you go. If you do the work yourself it isn't that hard and expensive to go back later.

George

I'm already down the slippery slope - the engine is completely apart.

The overwhelming response confirms my view - replace. I'd go with 993 steel studs if I can find any locally.

Interestingly, in their defense, the dilivar studs survived 240000 km and at least one previous "rebuild", but I'm not taking any further chances. I do believe that the dilivars suffer from stress corrosion cracking, but the car has not seen any of the nasty climates that you all are used to. No ocean air or salty roads up here.

Thanks everyone for the advice.

LeRoux

Hey LeRoux, talking weather, what's your summer been like? Ours has been hot, dry and not much wind (not much wind for a change!). And has that last kilometer or two of open space between Pretoria and Jo'burg been built over up yet?

I know that Jerry Woods replaces them with the stock steel studs that you already have in the top rows. I think going with the 993 stuff may be overkill.

George

The 993 steel studs were actually cheaper than the stock SC steel upper studs (I bought them from Pelican).
So..... the 993 sateel studs are less money, they fit just right, and are plenty strong and should never fail.
I like the cheep part the most ;)

The 993 studs in the Pelican catalog are listed as Dilivar not Steel.

The 993 steel studs (part # 993.101.172.02) aren't listed with the head studs. But you can "find" them in the catalog if you look for the fctory part number.
http://forums.pelicanparts.com/uploa...1109125841.jpg
-Chris

dats da ones. less than $10 each.

Bill, are you referring to 993 Dilavar or the steel 993 units that chris bennet is pointing to?

Bill

Summer has been great! Lots of rain up here during Dec/early Jan, then a dry spell until last weekend. Temps were mid 30's (celcius) during most of the dry spell. I spent most of December in Cape Town area, where the weather was equally good.

What open space?

LeRoux

993 studs are Dilivar steel studs.

Dilavar is a type of stainless steel, probably either a 300 series alloy derivitive or chromium/nickel alloy that is non-magnetic.

The 993 studs I installed were not stainless steel, they were carbon steel and are definately magnetic. Same as the oem upper studs.
They were not dilavar.

Absolutely, positively replace them. Use plain ol' steel ones. When you remove the old ones, use an oxy/acetylene torch to heat the area up along the edge of the spigot, about a half-minute to one minute, roughly. Then they will come out fine. Don't try this without heat. Propane will not come anywhere close to the heat you will need.

I used MAPP gas when I removed mine, not as hot as acetylene but much hotter than propane or butane.
Took a little longer (several minutes per stud) but the result was all good.
If you don't have access to an oxy-acetylene torch you can buy a MAPP gas setup at home depot for around $30.
If you break a stud off flush with the case because you didn't use heat, that $30 will look like a bargain.

Hee hee, It was a while ago when I was in the area and Pretoria and JHB were closing in fast. I did like the goverment house gardens and (spelling) Oum Paul's house.

(spelling) Moy Blay, Bill.

The studs have been replaced with regular steel ones. The old dilivars came out easily, surpringly perhaps. Maybe the car is starting to give me a break.

Thanks for everone's advise.

Bill, it's "mooi bly", but you get 9/10 for effort. :D :cool:

LeRoux