I had a blog site collection named http://abcd.net.au/sites/blog and had the blog site underneath it called http://abcd.net.au/sites/blog/test
I want to displays the blog Posts of tests on the sub-site Demo under main Intranet Portal http://abcd.net.au
Normally if you add the rss viewer web-part it will show all the fields related to ALLPOSTS view of the test blog.
In order to show the posts with only Title and body to the rss viewer webpart you have to follow this steps.
Go to the test blog Posts lists
Open the Posts List settings
under the column called Communications there is the RSS settings Option
Select the fields you want top display in the rss viewer webpart and hit ok.