The groove must be wide enough to allow the O-ring to be crunched when installed. If the groove is too narrow
the O-ring will have nowhere to go/expand and it will be cut when installed If the groove is too wide the O-ring will
loose crunch as it can wobble/snake in the groove.
Sorry for my bad tech terms, but try Google "O-ring groove design"
Here is a good site:
https://www.sealanddesign.com/page/o-ring-groove-design-metric/Rolf
That's what I've read, but being not a machinist, I wasn't sure I understood correctly
Thanks for the info.
I don't know if it is worthwhile to do it, but on the other hand, not a big job to do.