Cadillac Repair: 1979 buick, t rush, penetrant

Question
my exhaust manifold is leaking, before replacing gasket, i would like to check threads in head as i suspect they may be damaged. is the wall thickness around the thread big enough to allow rethreading with halicoils? engine size 6.6 litre.  is this common with this model? any other comments would be appreciated. i know this is a cadillac site however i'm told buick and cadillac come out of the same plant in the US.  any help appreciated.  thank you

Answer
Hi Ron, Stripping threads isn't too common. However after bolts have been in the head for a number of years the bolt will rust and sieze. If that happens and you try to force the bolt out then the threads could strip out. What I do is get a rust penetrant and spray the bolts real well and then work the bolt out. Other times useing a torch to heat up the bolt gets them out but you have to worry about wires and things getting damaged. Once you have the bolt out clean up the threads with a tap or you can heli-coil if the threads are damaged. Drilling at an angle always gives me fits so take your time and don't rush the heli-coil process. Sometimes it is best to remove the head so you get the angle you need. Hope that helps. Bill