Jerry - A quick scan through some Chevy books shows the following general details about the rear main journal diameter:

The large journal cranks have 2.650" mains. These were in the 400 cubic inch small blocks only. *
The medium journal cranks have 2.450" mains. These were in the small blocks starting in the 1968 and later model years. (1968 Chevy Truck Overhaul Manual says = 2.4479" - 2.4488")
The small journal cranks have 2.300" mains. These were in the small blocks built before 1955-67. *

* Granddaughter showed up for the day so I didn't have time to check actual books for details like found for the '68 and later cranks.

Hope this helps.


~ Dan
1951 Chevy 3 window 3100
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