The loctite was originally specified because it was something that was needed during the engine installation, and it would be needed for maintaining the engine in the future.
It works well if the fit of the busing is the desired level of clearance with the hole diam. that is specified, but apparently that can vary more than desired and some people have had them come loose, so the new plans for the iS airplane will be specifying using tank sealant.
It is fairly viscous so does a good job of gap filling if needed, and because it is flexible it will assure that differences in expansion/contraction will not be a factor (if there is a chance that that also was, but that is unknown).
Any opinions expressed in this message are my own and not necessarily those of my employer.
RV-6A (aka "Junkyard Special ")