Dilavar Cautionary Tale

[ischmitz]

What's the read stuff in the upper threads?

Ingo

[afterburn 549]

I am with ya!!!!!!!!!!!!!!!1

[Doug Zielke]

Originally posted by ischmitz
What's the read stuff in the upper threads?

Ingo

Dry-set Loctite.

[Bill Verburg]

Here is some interesting info that Bruce Anderson pulished in Pano 5/91

[Bobboloo]

False info - please don't misquote me.

The engine in the book was a 1974 2.7 engine. *ALL* magnesium cases will warp and deform - not just the 1975-76 ones (what about 1977) that you are referring to.

All of the 2.7 cases will show signs of warpage, and will require proper machining to return them to usable spec - not just the 2.7 cases...

-Wayne

I don't believe I ever quoted you. I refered to your book for machine costs which I did not quote.

The 2.7 motors 74' thru 76' used steel studs and either Nikasil or Alusil cylinders. (I should have included 74' in my previous post) In late 77' Porsche went to Dilivar top and bottom rows. I have one of those motors that hasn't been rebuilt and it doesn't leak oil. It's speculation, unless I teardown the motor and have the case measured, but I think there's a good possibility that it has survived without leaking partly due to the Dilivar studs, not pulling on the case as much every heat cycle the motor goes through, among other conditions such as not overheating. I give this info as a data point and nothing more.

As far as "all" mag cases warping. I have another data point. I have a 72' 2.4T MFI mag case motor that I rebuilt that I'm installing back in my Coupe. The pistons and cylinders and bearings were at the end of a long road and well beyond spec. The case, however, spec'd out fine. How is this possible since it's a mag case? Maybe it has something to do with the fact that it was built with iron cylinders that match up pretty close with the thermal expansion rate of the steel studs? Other factors I'm sure helped it survive such as not having thermal reactors and being a 2.4 MFI motor it runs pretty cool even without an external cooler.

My point is that I think it's short sighted for anyone to make a blanket statement concerning head studs. IMO choices are best made in a case by case motor by motor basis.

Interesting chart Bill. Makes a good arguement for the combination of Dilivar and Nikasil/Alusil cylinders.

[Wayne 962]

Bobboloo - You said that the engine rebuilt for the book was one that was a 1975-76 engine with the thermal reactors. This is not true, I just wanted to make sure that was clear. It was a 1974 2.7 911S engine (no thermal reactors).

My original statement: "All of the 2.7 cases will show signs of warpage, and will require proper machining to return them to usable spec - not just the 2.7 cases."

Some cases may be more warped than others. Some may have experienced greater heat stress. Some of them may be the stronger 7R cases, or the weaker earlier cases. However, they all bend/deform/stress in some way or another - it's the nature of the material. The degree of warpage depends a lot on the condition of the engine. 2.0L magnesium case motors (the lowest power mag-case engines) will also warp and bend to some degree - it's rare to see one not needing machine work. Ask Walt at Competition Engineering...

"In late 77' Porsche went to Dilivar top and bottom rows." - I don't think this is a true statement. To the best of my knowledge (and the information provided in original parts diagrams), Dilavar was only used on the bottom row for all production engines, with the exception of the 911 Turbo.

-Wayne

[Bobboloo]

Bobboloo - You said that the engine rebuilt for the book was one that was a 1975-76 engine with the thermal reactors. This is not true, I just wanted to make sure that was clear. It was a 1974 2.7 911S engine (no thermal reactors).

True. It's a point well taken. My mistake.

However, they all bend/deform/stress in some way or another - it's the nature of the material. The degree of warpage depends a lot on the condition of the engine.

Agreed. I used my 2.4T case as an example that not all mag case motors suffer the same fate so therefore should be judged accordingly when deciding which studs to use.

As far as the factory suppling Dilivar on top and bottom in late 77'. This was info that was given to me second hand so there is a possibility that it's in error. My 77' motor however does have Dilivar top and bottom row for what it's worth.

P.S. I rebuilt my 2.4T with stock P+C's (iron cylinders) and steel studs. The next motor I'm building however, a 2.8RS, I'm going with the latest Dilivars.