frankd

Can anyone tell me when the "7R" Magnesium case was introduced. My understanding that to convert a 2.4 L motor to a 2.7 or even a 2.8 ,using anything other then a 7R case will not be strong enough due the reinforcement of the 7R case.

Any thoughts would be helpful.

Thanks!!

Bill Verburg

The 7R case was introduced as part of the modifications for the 73 Carrera 2.7RS. As such it is the recommended starting point for any high performance 2.7 There are 2 versions of this casting

• 97mm spigots for 2.7 liter (90mm bore)
• 92mm spigots for 2-2.4 liter cylinders

the 7R case continued to be used thru 77

Chris Campbell

Bill -

Is there any externally-identifiable marking or part/type number distinguishing the two? Or do they need to be measured?

Thanx,

Steve Weiner-Rennsport Systems

Hi Chris;

If you look at the engine series numbers to the right of the fan that are stamped on the right case half, this will tell you which one you have.

You already know where the 7R numbers are,...
Here are some USA-spec ones to look for:

The 2.4's are a 911/50, 51, 52, 53, 61, 62, 63, 91.
These use the smaller (92mm) spigots but are more desireable since these cases do NOT show the same heat stresses that the 2.7's do, even though machine work is needed for the 90mm RS & 92mm RSR cylinders.

The 2.7's are a 911/41, 42, 43, 44, 46, 47, 48, 49, 82, 84, 85, 89, 90, 92, 93, 96, 97,

These have the 97mm spigots that will accept any 90mm cylinder and even the 92mm RSR ones without machine work. I would avoid the 76-77 ones if possible, as these cases almost always are warped and need LOTS of machine work to fix everything. BTDT,....

I do not recommend the 93mm 2.9 kits at all.