|
|
|
|
| Author |
|
|
Santa Clarita, Ca.
Join Date: Nov 2007
Location: Bakersfield, Ca.
Posts: 222
|
What's so special about a 7R case?
I've got a 2.4CIS that is a 7R case (73.5). Why is the 7R case so desirable? If I'm running CIS does it really matter what case I have/use?
|
||
03-10-2009, 05:00 PM
|
|
|
Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
|
The 7R case contained stiffening ribs and thicker walls (in some areas) than its predecessors.
These changes made the 7R a better candidate for larger-displacement, high RPM engines.
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
||
|
03-10-2009, 05:07 PM
|
|
|
Registered
Join Date: Oct 2004
Location: S California
Posts: 7,977
|
The 73.5 7R case is special because it has all the benefits of the stronger 7R case like Steve said but it also has the smaller spigots for the cylinders. In 74 they went to the 90mm pistons and opened up the spigots. So anyone that wants the stronger 7R case to build a 2.2 or 2.4 engine would want your case.
__________________
1970 911E Sportomatic Albert Blue 1971 911T Sunroof Coupe w/ Twin Plug 2.5 MFI 1973 911E Glacier Blue 1973 911E RSR Tribute Viper Green w/ 3.5 Twin Plug MFI |
||
|
03-11-2009, 10:52 PM
|
|
|
3 restos WIP = psycho
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
|
Yep - matter of fact Steve just did my small spigot 7R for a 2.3L ST motor I am building. This case was the best choice bassed on weight and the fact it has accomodation for an MFI pump (the early aluminum case doesn't - and it is heavier).
__________________
- 1965 911 - 1969 911S - 1980 911SC Targa - 1979 930 |
||
|
03-13-2009, 08:12 AM
|
|
|
JW Apostate
Join Date: May 2004
Location: Napa, Ca
Posts: 14,164
|
That's the same case my 2.6 is built on.
Just running it for the first time this week. KT
__________________
'74 914-6 2.6 SS #746 '01 Boxster |
||
|
03-16-2009, 09:29 PM
|
|
|
Registered
Join Date: Jan 2004
Location: CT
Posts: 11,557
|
Here's some pics showing the differences in the case structure between a 7R and an early mag case.
Note the extra reinforcing ribs in the 7R. 7R   Early Mag Case  
__________________
Tom Butler 1973 RSR Clone 1970 911E 914-6 GT Recreation in Process |
||
|
03-17-2009, 01:57 AM
|
|
|
|
Registered
Join Date: Feb 2003
Location: chicago
Posts: 1,077
|
is there a way to reduce the spigot diameter on a 74-77 7r case? i would think a sleeve would work. there is a set of 86.7mm st cylinders on ebay that require an odd size spigot - it would be a good use of a later 7r case i would think.
__________________
BMW 128i 73 rsr clone - sold 68 912 project to become 911r (almost done!) |
||
|
03-17-2009, 04:09 AM
|
|
|
3 restos WIP = psycho
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,665
|
Quote:
__________________
- 1965 911 - 1969 911S - 1980 911SC Targa - 1979 930 |
||
|
03-17-2009, 07:28 AM
|
|
|
Registered
Join Date: Mar 2004
Location: Seattle
Posts: 1,802
|
The other benefit of a 2.4 7R case like yours is it came off a car that did not have thermal reactors. Most of the later 7R cases used for the 2.7 liter mid year motors had thermal reactor in the exhaust, which led to higher motor operating temperatures, and more sever heat cycles for the case. This leads to faster wear and fatigue for the magnesium.
Or so I have been told.....
__________________
Brooke 1969 911 ST 2.8SS EFI ITB (Irish Green), 1974 911 3.6 ITB (Black) 1952 MG TD with F20C |
||
|
03-17-2009, 04:53 PM
|
|
|
Registered
Join Date: Aug 2001
Location: Tooele , Ut.
Posts: 428
|
4/5R is real close also, just missing the lower vertical gussets.
|
||
|
03-17-2009, 05:51 PM
|
|
