how can i fix my 2001 corsa utility ?

Hi guys my bakkie keeps pinging(very badly). Had da engine overhauled an it got quiet but its back same as before. I was told dat da cylinder head might be over skimmed an dat I must hav it measured. Can u tell me what da dimensions should be wen it cums to the height of the cylinder head. Thanks Don.2001 corsa 1.4i utility. N.B. It also miss-fires when I start it after a while den clears up.