what does 20 over mean

[dnoftz]

So i took my cylinder to my local machine shop today and they told me it is stock bore and that I need to have it bored 20 over to clean it out? so what size piston will I need. He said he cant do the bore untill I have the piston. so is that a 66.50mm or what. Sorry Im still learning at this stuff.

Also any one know where I can get a good piston at a lo lo price.

 

[CARNZ]

boring .020" over is .50mm over so order whatever piston is .50mm over what you have now, i dont remember stock blaster size lol

 

[Luni]

.020 over is twenty thousandths of an inch bigger around than stock. .020 is equal to .508mm or very close to half a mm.