When did Porsche switch to magnesium timing chain housings?

[L.a.Brooks]

Did Porsche switch to the mag housings for the 1968 model year or during the year at the same time they switched the engine cases to mag?
I have been looking for early aluminum chain housings with the five mounting bolts instead of the earlier three bolts and two pins. I have looked at dozens of housings and the only five bolt early housings that I've found are mag.
My 68S has a later mag case that I am switching back to it's original aluminum case. I was told that most of my cars original components are in the mag case engine that was with the car when I bought it. It has mag housings - could they be the originals off my engine or should they also be aluminum like the case?
I've included a picture of the housing mounting area of my aluminum case.

[raspy2point2]

I have a 68 911L with original aluminum case. It is Euro. I read some where that 68 cars with early aluminum cases already had some Mag parts like the breather vent on top of the engine. But do not know of other parts being Mag. Chris

[L.a.Brooks]

Yes, my car also has the Mag breather vent. I've been watching for an aluminum version, but now I'm inclined to think it is also original to my car. I am very curious to see the date stamps on my chain housings. I think Rothsport will be disassembling the mag engine next week. I will post what I find out. In the meantime I am still watching for aluminum 5 stud housings just in case I should have them on my engine.

By the way, I had a hard time turning the car off and pulling a strong engine that was running perfectly. It is such an exhilarating car to drive it took awhile to take that step. I did take one last adrenaline run just to warm up the oil before draining it :-). But now I'm looking forward to getting it back with it's original engine case back in it.

[gled49]

I don't think I've ever seen an ALU chain housing that would accept 5 studs/2hollow dowels of the late sand cast ALU crankcase or the Mag case. 68 is first year of Die Cast Mag chain housing.

[raspy2point2]

Ok I found a good source. PCA UP- FIXIN der PORSCHE Vol 6 ,Page 236 --permanent mold magnesium high-pressure castings in place of aluminum parts.This started after the beginning of the 1968 model year by replacing the castings of the chain housing,their covers, the engine breather, and the valve covers with magnesium castings. Chris