A little bit of information might be usefull when asking a question, like what engine you have, what year it is etc.

I'm guessing your replacing the cambelt yes?
 
its a 1.6s on a 51 plate, i lose all power when i go above 3000 revs and hae to stop turn car off and restart. have had AA ou 3 times and they can tell me whats wrong.

some one else on here had the same problem and it was the cam belt tensioner so was going to try that but the manual i brout and down loaded wont open so dont know ow t chage.
 
I cant see it being a cambelt tensioner personally, when was the cambelt last changed?

What is your engine code?
 
don't know was change before i brought it.

when the AA come out first time they told me it was the excaust, had the whole excaused changed at a very high cost and still not working cahnged the 02 sensors as well but still not working.

someone else on this forum had the same car with the same problem and it was the cambelt tensisioner

cant rember the codes