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Registered
Join Date: Oct 2005
Location: O-side California
Posts: 157
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Stability of mag case after machining / use for 10 years
Contemplating using a mag 2.7 7r case for a race application. Case was line bored, shuffle pinned, spigots decked. No issues for the last 30k miles in a street car with a nice cooler.
Question is: if I split the case now or in the future as pm will the case go out of alignment again and require re machining? What do mag case racers do? Is the answer that bottom ends are good for 250k miles so don’t split??? Probably. But if something happens ie bits in filter.... |
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03-21-2020, 09:20 AM
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Registered
Join Date: May 2004
Location: Boulder, Colorado
Posts: 7,275
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250K miles may be pushing it on a race motor. Porsche did build the 2.8RSRs on this mag case, but they used new cases, and didn't much care about longevity, not the street car variety anyway. And that was a one year of production motor, soon replaced with the 3.0 RSR and its aluminum case.
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03-21-2020, 09:44 PM
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Registered
Join Date: Oct 2005
Location: O-side California
Posts: 157
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Thank you Walt. I guess my question boils down to the following: if you are rebuilding after say 50 hours of use then is it expected to have to deck the cases and re alignbore every once in a while? Or at this point is the case stable? If you remove say 0.025 from the case mating surfaces every time you probably only have 2 align bores per case before the case is shot the why the sand casts are the best for racing...
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03-22-2020, 09:01 AM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,742
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I'd say it wouldn't be safe to assume that the case is OK since it was done at one time years ago.
I am rebuilding a later aluminum case motor that is shuffle pinned and presumably measured and had any other necessary procedures performed. After 70 hours of track use, it's back at the machine shop due to main bore measurements being out of spec. |
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03-22-2020, 10:14 AM
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Registered
Join Date: May 2004
Location: Boulder, Colorado
Posts: 7,275
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You need to hear from one of the engine rebuilders in the business, because they have the experience with enough cases to have a decent handle on things.
I gave up on mag cases for race motors quite a while ago when a couple of head stud inserts started backing out when I tried to remove them after the disaster of a missed shift. I think they are fine for street motors as long as you don't get ambitious. The 2.4s seem to hold up pretty well. |
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03-22-2020, 10:16 PM
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