Boring the fpp

[feartheride]

I need to bore outmy sons manifold and head pipe .Right now they are at 44mm with a bit of a bell mouth to 46mm.. if these were the old style that were at 42 originally ,can I bore out all the way to 48. What are the chances of breaking through the inner wall. I thought I read it was best to make it oval.. If so what size. I have read some of the older threads but as this is already ceramic coated I would hate to f it up...

 

[CARBONX2]

Go with 48mm circle. On the header you need to centralise it between the 3 bolt recesses, will be offset a bit to the original hole. Then cut gasket to match and use that to scribe the circle on the manifold, then it will all line up(make sure you keep the gasket facing to the relevant surfaces when marking the manifold).

 

[feartheride]

thanks carbonx2