I have a 1998 Ford F150 XLT4.6 Leter Triton V8 Engine.It starts and runs good until it warms up then it runs a little rough.I had the check Engine light come on so I had a Mechanic Check It.He said There is a Hair line crack in The Head on #4 Cylinder.I need some advice on Repair and how to retime the Head on this Engine?