Posts page image size

Hi there,

I am trying to solve an issue i’ve had for a bit. The featured images on my posts are 700×200, looks great on each individual post. However the issue is that on the posts page it uses the 600×400 portfolio image, whereas i want it to show the full sized image. Currently i’ve simply hidden the overfill, but i can’t find what file i need to edit in order to change this!

Thanks,
Joe

The page I need help with: [log in to see the link]