dilivar confusion, help

[coxy]

Rebuilding the top end on my 1987 3.2. Ready to change the head studs as is recommended in Wayne's book. Wayne mentions replacing all the studs (top and bottom) with std steel studs as used in the top row of a 3.2 or race wear studs due to the fact Dilivar are waiting time bomb. He also recommends 993 studs, yet these are listed also as dilavar(snap snap). Im confused.

So what do i do.?? Use all new std steel studs top and bottom?

Replace just the bottom studs with 993s ($$$) and keep original top row steel studs?


Or replace all with 993 studs

Race wear $$$$?

[tom1394racing]

For a stock motor, you'll be fine replacing your bottom row with OEM steel studs like your top row.

[Flieger]

Dilavar 993 studs all around is best. (though $$$$)

Steel is ok for a stock spec motor.

[lucittm]

coxy,
I don't think your question was answered. There are two types of Dilavar. The first was the Porsche factory solution to the lower head studs pulling the threads out of the engine crankcase in the magnesium engines. This problem also emerged as the compression and engine size increased in the aluminum-cased engines. These new metal studs were installed by the factory beginning in 1984. I think these were P/N 993-101-170-51, fully threaded Dilavar ($37.00). The upper studs were still steel, P/N 911-101-172-00 ($10.75) in all cars except the turbo which used all Dilavar studs.
There were corrosion problems with the initial Dilavar studs in some extreme circumstances and the factory reverted back to coated steel, P/N 10-0115-101 ($14.00) for all but the turbo cars. The second type of Dilavar studs were re-engineered for the turbo engines five years later, in 1989, P/N 993-101-170-53 ($43.00) and seem to hold up well.
In many engines, the studs have been replaced so you may have Dilavar studs in an early non-turbo car or steel studs in a turbo. I believe I have the 993TT studs in my car, they are reduced-diameter, coated black and a magnet will not stick to them.
Some people claim the Dilavar studs are too brittle and they break. There are just too many variables such as improper torque, abnormal engine stress, overheating, etc. to fault the metalurgy. Metal fatigue certainly plays a factor, but when the Porsche engineers found a strong metal (up to 170,000 psi) that expanded at about the same rate as all the aluminum in the flat six engine, I think that was a real accomplishment.
This information is based on the PP website and books I have read on the subject and not my personal experience, so don't hold me up to any of this.

Good Luck,
Mark

[Flat6pac]

The 993 studs, black and threaded the full length pull a magnet so they have to be steel. At this point there is little use for them over standard steel.

[Schwarzeritter]

The 993TT units, but to that I think it is some what to the engine builders discretion or prefference rather.

[Henry Schmidt]

The Supertec head stud kit is the best choice for all air cooled 911 based engines. Used by top engine builders around the world.
The only head studs on the market designed with modern stud technology. No more goofy allen nuts, no more measuring stud installation length, no more shuffling heads.
The debate goes on but after building more than 400+ 911 engine we have no trouble making the intelligent decision.
They are available right here from our host, Pelican Parts.

[lucittm]

Henry,
I'm glad you jumped in here. No discussion of head stud replacement would be complete without your Supertech Performance blurb.

Mark

[Flieger]

The choice is a matter of engine-builder debate/opinion.

Henry, I think your stud is already broken and it hasn't even been run in an engine