2003 GT purchased about 3 months ago.Has 54K on it. Since I had no history on the car, I decided to change the plugs. I had an issue with the second from the firewall on the passengers side. The one with the fuel rail in the way. I could not get it out. Long story short, the person that changed them before me must have crossed the threads on the head. I barely got the new one in. It lasted for about a month and blew out. I can't get another plug in because the threads are jacked up big time now. I am bringing it to my mechanic. He is real good and I have been going to him with all my cars for years. I am hoping he can get a Helicoil or a Time-sert (preferred) in there without pulling the head. It looks like its going to be tough. Anyway, if he has to pull the head, about how many hours would that be? Just trying to prepare myself and my wallet for a major setback. It looks like a big job.

 

I think its possible to do a helicoil with the head still installed, now I'm not sure but I thought I rear somehwere that the head had to removed to use a timersert, which is the better option, but don't quote me on that. As far as labor to removed the head you might as well figure it will be about the same cost in labor to replace a head gasket so roughly 900-1500 at a shop. The joys of overhead cam head removal.

 

I blew out my #5 plug on my Paxton equipped Mustang last year. Yes you can use a heli-coil without pulling the head, I did it in about an hour, taking my time.
Don't think you can install a time-cert without pulling the head though.
Mine has held up well, got about 10k miles on her since I repaired it. Good luck my friend.

 

Thanks for the input. I dropped the car off today. I mentioned the time-cert to him. He just kind of ignored it. Then a bit later told me he was going to drill it out and put a helicoil in so I guess that's what he prefers. Probably trying to save me money by not pulling the head. I heard from others that to use a time-cert, you need to pull the head. I just want it to last. He mentioned something about securing it with loctite and then hitting it with a punch to secure it into the head. As long as it doesn't blow out again, I really don't care. The car is bone stock so I am hoping I won't have any problems.