r case designations

BReyes · BReyes's Garage

What is the difference between 1r 2r 3r etc to 7r. I have some motor rebuild projects going and when i buy next early motor(s). Or if can remind me what book infi is it located in. I have about 20 porsche books at my other home and five or six with me presently.

(i) a 3.2 l being refurbished- I would say it is more than 7r. Like a 2.7 l is 7r (my memory is coming back to me vaguely on their differences but would like to learn more).

(ii)an unknown motor that I need to look at closer.

And (iii) a 2.2l 5r.

Regards,

tom1394racing · 02:43 AM

Here's some pics showing the differences between several types of 911 crankcases.

2R Case - These are the early Mag cases generally found on the 2.0 and 2.2 engines from 1969-1971. These generally do not have the piston squirters which were introduced in 1971.

tom1394racing · 06-16-2007, 02:17 AM

3R Case - I have seen these mostly on the 71-73 2.2/2.4 liter engines.

These generally have piston squirters. I am not sure what the other differences between the 2R and the 3R cases are.

tom1394racing · 06-16-2007, 02:25 AM

2.4 7R Case - These are relatively rare 7R cases that were used in the latter half of 1973 for the 2.4 engines only. These have the same stiffening features as the 2.7 7R cases but these cases use the smaller 92mm spigot bore.

Note the extra stiffening ribs inside the case and at the flywheel end of the case.

tom1394racing · 06-16-2007, 02:33 AM

2.7 7R Case

These cases were used for all the 2.7 engines from 74-77 and for the 1973 2.7 RS.

These are the same as the 2.4 7R cases except for the 97mm spigot bore. In 1976 Porsche introduced the oil bypass modification on these cases.

tom1394racing · 06-16-2007, 02:42 AM

1978-83 SC Aluminum Case - These cases were made out of aluminum and are around 20 lbs heavier than the magnesium cases. They are also much stronger.

BReyes · BReyes's Garage

Appreciate the info. Relearning is fun. Can actually see the larger picture.

Thanks you.

Lemans 2007: Go Singer with Long!

rfuerst911sc · 06-16-2007, 08:48 AM

I was talking recently to a well respected performance machine shop in Tavares Florida recently and they are not building any Porsche performance/race engines based on the mag cases. They said they are seeing too many cases where they are disintegrating into powder in some areas. I'm not sure how prevalant this is but I would suggest anyone looking at mag cases inspect them well. The 3rd pic listed here on the 3R case shows signs of the white powdery breakdown of the metal.

kucharskimb · 06-20-2007, 07:47 PM

healthy oil leaks will keep the oxidation in check

blue72s · 07-24-2014, 10:56 AM

What is the difference between 1R and 2R?

RoguePorsche · 08-21-2015, 03:02 PM

2.7 7R Case

These cases were used for all the 2.7 engines from 74-77 and for the 1973 2.7 RS.

These are the same as the 2.4 7R cases except for the 97mm spigot bore. In 1976 Porsche introduced the oil bypass modification on these cases.

Anyone know the pro's & con's of this???

Flieger · Flieger's Garage

Best of the magnesium cases except for the ones that were cooked by thermal reactors.