Case Saver Experience, magnesium cases.
 

I'm facing replacement of case savers installed two years ago. The whole sad tale, for anyone interested, is here ... http://forums.pelicanparts.com/911-engine-rebuilding-forum/371883-head-gaskets-destroyed-but-why-74-2-7-911-a.html
My question is, has anyone had experience with redoing case savers? Apparently the old ones are drilled out and new, larger units are installed. Obviously I'm trying to figure out how reliable a repair this will be. Any insight welcome.

While I cannot respond with personal experience, I know that a local shop owner commonly used, and requested the second oversize ones. When I heard him request this from the machine shop, I inquired. He said it's been his experience that the oversize is a safer route. He mentioned having earlier motors come back with pulled inserts, and the "come-back" costs are too severe to take the chance. I hope some of the pros will chime-in on this for you.

You are probably better off getting another case. This time I would use Dilivar studs. I think they are the only safe bet for high power 2.7 engines.

-Andy

The REAL key for preventing such issues with these magnesium cases is strict control of oil temps.

We use steel studs in these where the oil temps will be maintained below 200 deg F. The later Dilavars are OK too, but not a substitute for having an effective oil cooling setup. :)

Oil temp on this motor hit 250 once for a minute on the track then was brought in to cool. Other than that, it has never been over 225°, and that rarely. If that's too much I need to rethink my oil cooler setup, along with everything else. Thanks everyone.

I assume your not using the 5 blade fan?

Yes. Have the more potent fan. Oil cooler is Earls, -16 lines fore and aft. With cooler connected and working properly 225 is about all I ever see.

Jim:

250 deg F, while tolerable for the aluminum-cased engines, is FAR FAR too hot for any mag-cased motors and those temps really loosen everything as well as facilitate case warpage. I'm not comfortable about running at 225, either.

My very best advice for you is to add oil cooling capacity (airflow,...anything!) to ensure that your oil temps stay below 200 F.

Mag-cased motors are very durable with STRICT oil temp controls,..:) :)

EUREKA. There's nothing wrong with my casesavers... they are the proper 14mm size with proper pitch and are very firmly in place. Remaining theories for what went wrong here: 1) the cylinders are of different lengths. 2) the "deck" on which the cylinders sit is misaligned. 3) the heads were torqued properly but with a wrench that was out of calibration. We'll know more next week. I'm hoping it's 1 or 2 so as to really have identified the cause. Anyway an expensive bill has been reduced by a good deal. Now to think about Steve's temperature point.