Crankcase Observation

[Bob Goding]

I have often pondered the fact that the 911 crankcase does not have a positive locater for the two halves at the mainbearings.
The thrubolt holes are 12 mm and the bolt shank diameter is only 7.5 mm to let the oil flow.
These engines dont seem to have many problems in service though,perhaps the flat arrangement keeps them stable .
I would have thought that 'shufflepinning' would be a logical
thing to do,at least on a Magnesium case, but Bruce's Bible mentions that it shouldnt be done or is not necessary on a standard performance engine.
Any comments from the experienced,on this design feature?

Bob '76 2.7s

[John Druckrey]

Take out all of the studs - goes together quite easily. All kidding aside I am having the same problem with my case (a 7R). I stripped it down so that I can send it out and have it trued and squared. I did notice that a few of the studs which I had removed were bent - that probably had something to do with the "misalignment"

[ChrisBennet]

I think Bruce said that it wasn't advisable to do on an aluminum case. I'm too lazy to look up the quote.
-Chris

[John Druckrey]

So you're saying that it would be appropriate to pin a magnesium 7R case?

[cgarr]

Porsche used a positive locater on the 912 engines called a fitting bushing just on the center main bearing, its just a hardened steel bushing thats machined right into the thru bolt hole and holds the alignment, looks super easy to duplicate on a 911 case, im suprised they didnt do it since there a lot more mains on the 911

Craig

[ChrisBennet]

Originally posted by John Druckrey
So you're saying that it would be appropriate to pin a magnesium 7R case?

As far as I know, yes. I think to do it properly you pin it and then true/cut the main journal. Waaay off my map of experience though so I would investigate further if I was you.
-Chris

[John Druckrey]

My 7R case has the bushings (at least two) that cgarr refers to although I don't think they are on the center mains.