A dumb question
 

I see people advertising that their rebuilt motor has a 7R Mag case. What is a 7R Mag case? How is it different from any other Mag case? Just curious
Thanks

They where the strongest of the mag cases had some extra reinforcement for bearing saddles et.

The 7R refers to the p/n on the case. There were small differences between the cases like the addition of piston squirters in 71 or oil bypass in 76. I think Porsche used mag cases up through the 1977 2.7. Here's the write-up Tom Butler did on the differences.