Hi OttoRobba,
D'oh. Sorry, I forgot all about the built-in timeline. :)
To do a timeline for the portfolio:
1) Open template-post-timeline.php, save as template-portfolio-timeline.php
2) At the top template-portfolio-timeline.php replace
/*
Template Name: Post Timeline
*/
with
/*
Template Name: Portfolio Timeline
*/
3) Replace this line
query_posts(array('posts_per_page'=>-1));
with this line
query_posts(array('post_type' => 'portfolio','posts_per_page'=>-1));
4) Upload your new template to the theme directory then go to Pages > Your Timeline Page and select Portfolio Timeline from the drop down list under "Templates" in the "Page Attributes" box.
That's it.
Regards,
Mya