Help needed removing cat converter

[hoggaz]

On my 172 I'm finding it extremely hard to undo the bolts holding the manifold and cat together. There isn't a great lot of room to work with and I fear I might have rounded one of the bolts. I tried removing the heat shield above the cat but couldn't see how to take it off as the gear leaver comes though it. Is there any technique or tricks to getting it off?

 

[len_beach]

Jack it up. One person lays on their back with a 1/4 inch drive 10mm socket on a very long extension. Another person sits on the slam panel leaning over the back of the engine holding another 1/4 drive deep 10mm socket onto a small breaker bar on the bolt heads. You then undo from underneath.

It will take you between 2 and 3 hours if you haven't done it before.