R975 Radial engines

[Bob Phillips]

I have included some photos of the 975 rear main bearings. I am looking for some expertise from the forum readers if you can help. Both the C1 and C4 engine use very similar bearings- and while I have a large number of misc bearings the only difference I can see is the addition of the large slot/notch on some of these bearings. Can anyone verify whether C1 and C4 bearings ( which have different parts numbers in the manual) are in fact interchangable? You can clearly see a narrow keyway and the larger notch in the photos.

bearing1.jpg bearing2.jpg bearing3.jpg

Just an update... The bearing with both slot and oval notch as shown is for a C1 engine. A bearing with only the slot is for a C4 engine.
A bearing for C1 will apparently fit and work in a C4 engine but a C4, lacking the oval notch, will not work in a C1 engine.