#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

[Walt Fricke]

The #8 bearing for my '82 SC motor is identical to the #8s from my 1977, and from a Grady Clay short stroke 2.5 (66x88mm). When I rebuilt the SC in 1989 or so, I used the larger, newer style, O ring. All these #8s are identical. Same with the 2.7 and 2.8 race motors, which had #8s from engines earlier than the SCs. No issue I can see to using the 51x4.5mm O ring in every air cooled 911. They all seem to accept the same #8, with the latest PN being a 964 part. However, my hands on experience stops with the SCs.

When I heard (can't find where)that Porsche had switched to the slightly larger O ring for the SCs, and its use was recommended on the older cars, I began using that on my older engines, with no issues. Anything to avoid a leak past this ring.

[356911930]

Thanks Walt! I was hoping that you would reply as I recall it was your thread that I first read about the updated O-ring being used for the #8 main bearing. My gasket kit from EBS appears to only have the 50 x 4.0 mm O-ring in the kit so it looks like I will need to order it separately from our host.

Thanks again,

Rahl