#8 Main Bearing O-ring

[356911930]

This is a crosspost from the turbo section.

The earlier 911/930 used an O-ring for the #8 main bearing that was 50mm x 4.0mm. The newer 911/930, I think about 1984-86 and later used a #8 bearing O-ring that is 51mm x 4.5mm. I read on another thread that the newer #8 main bearing 51mm x 4.5 can be used on the earlier engines. Was there a change in the #8 main bearing O-ring groove dimensions or does the newer 51mm x 4.5mm O-ring just happen to fit in the same size O-ring groove that the 50mm x 4.0mm fit in the #8 main bearing? Usually O-ring groves are specifically sized to fit a specific O-ring.

Any experience with this issue?

Rahl

[Flat6pac]

There is definitely a size difference between early and later #8 bearings
I think I Would want to look at the two O rings in place. I like the idea of the extra half mm
Bruce

[Eagledriver]

Don’t try to use the bigger o-ring in an early engine. It will pinch out into the seam. Don’t ask me how I know!