7R case

[chrisf]

I've heard mention of the 7R case. They are the last numbers on my case, 1976 2.7L.

What does this designate? And what are the benefits over other cases for these years/sizes?

[Bill Verburg]

Over the years there were several different castings used for the Mg. case. 7R was the final, strongest version, it was introduced in MY73 for use on the 2.7RS engine but was also used on the late 2.4s, it continued in production through My77.

The best ones are generally considered to be from the late 2.4s because they ran coolest and stressed the c/c least. Of course individual blocks have widely varying histories so an evaluation of the particular block should be done.