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Thread: Case Transition 4R/5R to 7R

  1. 05-01-2008, 11:34 PM #1
    Guru
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    Case Transition 4R/5R to 7R

    While working on my car (seems to take forever!), my mechanic is also starting on another car which will require a replacement case and needs some advice on which version would be appropriate. He asked me if I could pass this question on to the experts at the S Registry:

    Does anyone know when exactly the engine case transitions took place between the following versions

    - 4R/5R without reinforced "ribs"
    - 4R/5R with reinforced "ribs"
    - 7R with 92 mm cylinder base
    - 7R with 97 mm cylinder base

    My car (chassis 9112300871, engine 6321334) has a 4R/5R case, but I understand the 7R started coming in around 1973. Any idea on dates / chassis numbers where the changes took place?

    Thanks for your help!


    Best regards, Guru
    Guru Sivaraman

    1972 S
    1977 3.0 Carrera

    Early S Reg. #1199
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  2. 05-02-2008, 05:11 AM #2
    Zithlord
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    7R Mag cases after mid-March '73, but some mix'd in allready from Des72/Jan73. read these treads:

    http://www.early911sregistry.org/for...hlight=4R%2F5R

    http://www.early911sregistry.org/for...hlight=4R%2F5R

    John
    Early 911S Registry #931
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  3. 05-02-2008, 06:44 AM #3
    Guru
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    John,

    Thanks for the help! I did search but missed that useful second thread. "7R" is not allowed as a search term

    Does anyone know about the reinforced and non-reinforced 4R/5R cases or about the two types of 7R cylinder base my mechanic referred to?

    Guru
    Guru Sivaraman

    1972 S
    1977 3.0 Carrera

    Early S Reg. #1199
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  4. 05-05-2008, 06:44 AM #4
    jameshtaylor
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    Bruce's book has useful information somewhere in the engine evolution section about the two 7R cases.
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