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lucittm lucittm is offline
Manassas, VA
 
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Join Date: Apr 2007
Posts: 1,211
Garage
Although it is poorly worded, this could be a reference to the different sized M/C bores. For the 911 and 912, from 1965-67 the bore was 17mm - 901-355-011-01.
In 1968, it was changed to 19mm - 911-355-012-02. Then in 1977 vacuum power assist was introduced with the 20mm bore - 911-355-011-12 (the turbo was the same in 1976-77 but changed to a 23mm dual circuit version - 930-355-011-03 from 1978-89).
In 1989-94, the Carrera 4, and the new 965 turbo introduced in 1991, used a new 23mm hydraulic power assist unit - 964-355-903-00. In 1990, the Carrera 2 used a 20mm unit - 964-355-015-03 until 1994.
In 1992 the RS came with a 25mm master cylinder and the 993 followed with the same size in 1994.

Mark
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1991 964 Polar Silver Metallic Turbo Coupe
Old 01-26-2009, 10:00 AM
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