Remember: a custom field is an extension to the data MODEL. There is nothing inherent in that which specifies how it is FORMATTED. So a “table” is definitely part of the view, and as such, it’s entirely up to you as to how you want to format it.
It’s much easier if your model is static (i.e. has the same fields for each product). Once you’ve wandered into an area where some products have some fields and other products have other fields, your data model isn’t necessarily defining the same object and things get weird… this sounds an awful lot like you could use WP’s original “Custom Field” functionality (i.e. add as many fields as you want and use whatever name you want)… and that may solve one problem, but it causes lots of others.
A simple solution to this might be to add a textarea or WYSIWYG field for your product specs. The only reason to break this down into multiple fields would be if you required searches across a given spec (e.g. show me all products with a torque of 10 to 20 foot-pounds). I’m talking *required*, not just “nice to have” because those types of custom searches are tough to code.
The closest you could do currently would be using the Relation-Meta field, but I hesitate to recommend that because it’s overkill for this type of thing and it would require a lot of customizations in your templates… it would be an overly heavy format for your manager.
There is a feature request for a “table” field that would let you add rows to a single table object: https://code.google.com/p/wordpress-custom-content-type-manager/issues/detail?id=392
