Wow, I let this one go a bit. It's an ETT1 carter with a throttle shaft body intended for use with a governor. The entire screw head just sheared off of it. I ended up getting another throttle body assembly and nearly did the same thing. There's always one screw that gets jammed, but that's got to be due to my inexperience. I wouldn't think it would be so hard to get a screw out though without tearing it to shreds.