How to check a warped cylinder head
A warped cylinder head is quite common with aluminum head. It is normally caused by an overheating engine. When the engine overheat it can cause the head to warped and have uneven surface. The best way to fix a warped cylinder heat is to take it to a machine shop where they can check the warpage. However, a person can check the warped cylinder head themselves by using a straightedge.
A straightedge is a metal ruler with a flat edge. To check for warpage, place the straightedge across the cylinder head from one end to another. Use a feeler gauge and place it under between the head and ruler. This will give a person and idea of the gap. Continue to check from one end to another and measure the difference. If the difference is noticeably, the head is warped and needs to be milled.
The benefit of having a perfectly flat cylinder head is to provide a better seal between the block and the head. This will help prevent head gasket from being blown out.