case #'s

[Dave Pugh]

What are the engine case numbers for 911S, 911T and 911E for 1973? Thanks for your help.

[EARLY911ZOO]

the second number indicates model
613xxxxx for T
623xxxxx for E
633xxxxx for the S
third number is the year

[fryardds]

Also there are type #s

911/57 for non-US T
911/51 for US T (MFI)
911/91 for CIS T
911/52 for E
911/53 for S

[Dave Pugh]

More specific the number on the case 5R or 7R? Do those numbers mean anything? I've heard 7R means 2.7? Is 5R 2.4?

[Flieger]

The numbers changed throughout casting design revisions. The higher the number, the better, basically. The 7R Magnesium case has many more reinforcement ribs which add stiffness and resist heat deformation. It also weighs a couple pounds more, but still lighter than the Aluminum cases.

[Dave Pugh]

So the 7R is an S case for 2.4 or is it a 2.7

[Flieger]

I believe it is a 2,7. I think 5R is 2,4. I am not much on originality/correctness, only performance, so I am not the person to ask on those matters.

[CamBiscuit]

The 7R can also be a late 2.4 case, not necessarily an S. I.e. 911/91 used a 7R case

[fryardds]

Right, the transition from 5R to 7R is more date of production related ('72 and '73) than model specific as far as I know.

For instance my RS has a 5R case with a mid January '73 production for the car. I haven't looked at the date when the case was produced by Mahle but maybe others have and know when the date of casting change was made. I'm pretty confident the casting change was made in '73 and not '72.

[210bhp]

Brian

Just to throw a spanner into the works my case halves (RS production May 73) are 4R and 5R and they are original. I too have not looked at the production date but I would imagine this would not help either as my case is a bit special.

This (and many more details) I would love to compare with Jol's car (sister RS to mine). Where is he now?

So, Dave you are not going to get the clear definitive answer you are looking for to this question because there isn't one.

Regards
Mike