My GMC had really old gas in it and when I got it good and warm the varnish from the tank got all around the valves. After it cooled down the varnish glued the valves tight.Bent all the pushrods. The machine shop had to boil the head for two days just to get it apart. I did'nt need a valve job before that. I wont ever start one on old gas again. Cost me a lot of money just to be impatient.
