I will tell you this if the plug is longer than the hole it does nothing for you in keeping it in the hole. However after 100,000 more miles it can strip out the threads. What happens is the extra threads on the plug collect carbon then get real hard. When you break the plug loose and back it out the carbon opens the threads in the head. Your best bet is to get them the correct length. Or better yet when you remove them turn them 1/2 turn out then spay some lube or cleaner down the hole and wait an hour then tighten them up LIGHTLY. Then turn out 1/2 turn and spary a little more wait 1/2 hour then back them out. You will not make the threads larger hopfully and you will avoid a blown plug.
This happens on aluminium heads all the time. Thats why they have helicoils.
Well, I actually got them in and the code stays cleared!
I learned to do the superman pose for those rear most plugs. The items posted hear were a great help. In my observations, I found that even after using an air hose to blow out the plug holes, after removing the COPs, I found dirt in the hole when installing the new plugs.
It's very difficult to get an air hose in to where you need it. A flex hose or small bent air hose would be useful perhaps. And if I did this again, I might even look at some type of pressure cleaner then air hose treatment. Just a thought.
I took my time. I haven't done back arches in some years. And patience is required.
I dropped a power streering bracket bolt into bolt heaven, and found that the dealerships turn their nose up quite abusively if you're looking for a bolt.
I still haven't found an 8mm bolt.
But other than these things, I'm amazed that it went back together as uneventfully as it did.
It's a toss up to me whether to pay for four hours or to do it yourself. Atleast I know (think) that they are not cross threaded, and they have been installed with anti-seize compound. And they were infact installed!