Groove beside No.1 main Bearing

[76 West&East]

A friend of mine is rebuilding 67MY 911 engine and is closing cylinder block case.
I find the groove beside No.1 main bearing. It's around cylinder through bolt hole and the hole is used for oil passage, too. The groove seems to be for O-ring to seal oil pasage, But Wayne's book does NOT refer.

Per the groove size , depth and diameter, I find a reasonable O-ring on NOK parts book. But the groove is not pefect circle and a part of the circle does not exist. It means if I install the O-ring, it does not have reasonable compression at the circle lacking portion.

Does anyone has know- how about the groove?

Thanks

[cstreit]

If the one you're refering to is on the case edge, this is for oil seeping out of the oil through passage there to end up back in the case. That groove surrounds the passage and notched back into the case area. If the groove wasn't there, oil seeping out of that location could equally force out of the case havles instead of back in. Just make sure your case sealant is consistent on the outside edge.

[76 West&East]

This is the groove I am talking about. See attached picture , white circle

Thanks

[cstreit]

Yep.

[Wayne 962]

I do reference this somewhere in the book - but in the text, not a photo. It's an oil pressure relief cutout in the case - just make sure it's not clogged with case sealant, if you don't use the 574. The 574 shouldn't harden when it's not in contact with metal, so even if you get some in there, it should just wash out with oil when the engine is run.

-Wayne

[76 West&East]

Thank you for your advice.