Hi,
You need to edit the “CustomParts Imperial Catalog.pcat” and/or “CustomParts Metric Catalog.pcat” that are located in the folder "C:\AutoCAD Plant 3D 2013 Content\CPak Common".
Once you have done that you need to update the specs that are stored here (CustomParts Imperial.pspx and/or CustomParts Metric.pspx😞
C:\AutoCAD Plant 3D 2013 Content\CPak Common\CustomPartsSpecs.
I hope this helps.
Dan
Dan Scales