hi guys
one off my lower engine mounting bolts head has rounded off
its the last one to loosen to drop engine on my nc21 to put new collector
box on
tryed everything
mole grips pro socket impact socket any ideas
cheers

Tried heat and hitting it?

+1

heat it up, then spray penitrating fluid on it, then hit it.

Centre punch the head then drill it off.

cheers guys will give this a go during the week
i"ve been told about these easy out sockets anyone used them
thanks again

Also as it's the last bolt it may also help to support the weight as this will also put load on the bolt which will make it tighter/harder to move. Get some plus gas penatron anything like that. What size head is it could you go for an imperial size? or dremmel some flats on it is a possibility.