Post images are being resized to 640 x 427

I’m not quite sure how to describe my problem, so sorry if this seems confusing.

Basically, no matter what size I make an image in a post, anything larger than 640 x 427 will get down-sized to this dimension. I finally found in the HTML this:

<img class="fullwidth aligncenter wp-image-149 size-full" src="http://i1.wp.com/www.vanagon.org/wp-content/uploads/2013/05/Flow-of-Fuel-System.jpg?resize=640%2C427" alt="Flow-of-Fuel-System" width="1108" height="739">

As you can see, somewhere in the theme it’s overriding my changes with the “resize=640%2C427”. I have searched high and low and cannot figure out how to get rid of this resizing.

My end goal is to have images display full width inside each post. The img class “fullwidth” is something I created to accomplish this. However, Inkness is simply pulling the resized 640 x 427 and stretching it to fit the larger dimension making the image blurry. Hopefully this makes sense by looking at a blog post here:

http://www.vanagon.org/fuel-line-replacement/

You can see the image is blurry, but if you go to the source code the image is nice and sharp:

http://i1.wp.com/www.vanagon.org/wp-content/uploads/2013/05/Flow-of-Fuel-System.jpg