930 47mm four journal cam towers

[74Targa911]

Hello to all. I am in the process of putting my 1974 911 targa back on the road. I decided to do a mild street build with the 2.7. Valve job, valves guides, valves, 2.8 JE 9.5:1 pistons, nickies, and a set of 147 and 148 SC cams. The cams have the later 49mm journals which do not work with my early 47mm journal cam towers. So I went on the auction site and found a set of four journal 930 cam towers from what was supposed to be a 1982 SC.

The towers arrived today, and much to my dismay they are indeed four journal towers, but they are only 47mm and my SC cams don’t fit. I know that sometime in 1977 they changed from three to four journal towers, and the early four journal models retained the 47mm diameter. Part number is 930.105.111.0R. All four journals are drilled for oil and the date stamp is from 1982. My theory is that these towers are replacement 77 parts manufactured in 1982. I called the seller and he couldn’t seem to wrap his head around the fact that these towers most likely weren’t from an 82 SC.

What do I have here? Is my replacement part theory correct? Were any early SC cams made with 47mm journals? Or are ALL SC cams 49mm journals? Any help would be greatly appreciated.

[faapgar]

All 2.7 through 77 were 47mm.3.0 Carerra 76-77 were 49mm.SC 78 & up were 49mm.You have replacement towers made in 82 for 2.7.Cam towers are a wear item and rarely inspected for line bore trueness.When you have a broken head stud the problems begin.Fred

[gled49]

+1 what faapgar said. I have a 47mm tower with 964 casting numbers.