Head Studs Coating

[dennisv]

Did the original steel head studs not have any form of protective coating? I cleaned the ones I pulled off our engine. Didn't appear to be plated. Within a couple hours some surface rust started to form. I brushed it off and lightly coated them in oil for the time being. Not sure what the long term solution should be.

[jess p]

Not sure about the original ones but I’ve bought new head studs for my 2.7, 3.0 and 3.2 and they are coated.

[Flat6pac]

Original Porsche studs are non coated steel.
Bruce

Sorry for the original misprint

[PeteKz]

You didn’t say what engine. Original Steel studs usually have a back oxide coating. I like to paint them anyway. Although I haven’t personally seen broken steel studs, they do break. corrosion can cause stress concentration and cracking, so I figure a coat of engine paint can’t hurt and should help. .

[stownsen914]

I've seen early steel studs that at a casual glance appeared to be bare steel. That may well be wrong, perhaps they were oxide coated at PeteKz suggests. Or maybe the coating was worn off.

[dennisv]

Originally Posted by PeteKz

You didn’t say what engine. Original Steel studs usually have a back oxide coating. I like to paint them anyway. Although I haven’t personally seen broken steel studs, they do break. corrosion can cause stress concentration and cracking, so I figure a coat of engine paint can’t hurt and should help. .

It's a 914-6 engine (aka 1969 911T). I could see them being black oxide. Certainly don't seem to be zinc or cad plated.

Originally Posted by stownsen914

I've seen early steel studs that at a casual glance appeared to be bare steel. That may well be wrong, perhaps they were oxide coated at PeteKz suggests. Or maybe the coating was worn off.

I think our case through bolts are bare steel.

[stownsen914]

Thru bolts are bare metal, yes

[john walker's workshop]

They all looked surface rusty to me, to various degrees.

[Henry Schmidt]

I love threads about head studs.
Simply put, early steel studs were heat treated before thread rolled. Hence the black appearance.
The next iteration of head stud was the gen 1 Dilavar. It was cad plated silver. If they were not baked after plating, they could have suffered from nitrogen embrittlement.
These studs were prone to breaking so Porsche decided the produce the same stud (cad plated) but added a coating of black epoxy. They still broke so for a short time they went back to the ht plain steel. Because of ensuing warranty issues they decided to try a new design Dilavar stud. This new monstrosity was an all thread/cad plated, epoxy coated stud, this one incapable of creating a truly stable head the cylinder connection. When they ended the air cooled engine, all head studs were returned to a more predictable steel alloy (all be it, heinous all thread), even in the Mezger engines like twin turbos and GT3.

[mikedsilva]

Originally Posted by Henry Schmidt

I love threads about head studs.
Simply put, early steel studs were heat treated before thread rolled. Hence the black appearance.
The next iteration of head stud was the gen 1 Dilavar. It was cad plated silver. If they were not baked after plating, they could have suffered from nitrogen embrittlement.
These studs were prone to breaking so Porsche decided the produce the same stud (cad plated) but added a coating of black epoxy. They still broke so for a short time they went back to the ht plain steel. Because of ensuing warranty issues they decided to try a new design Dilavar stud. This new monstrosity was an all thread/cad plated, epoxy coated stud, this one incapable of creating a truly stable head the cylinder connection. When they ended the air cooled engine, all head studs were returned to a more predictable steel alloy (all be it, heinous all thread), even in the Mezger engines like twin turbos and GT3.

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