This post is for the benefit of quiet members who own 2005 to 2010 4.6L 3 valve V8 GT’s.
Most in the group of regular posters will already know this information. However, it is information that is getting old and can be forgotten.
The registration thread for the Amherst spring run gives a glimpse at the many members who read on this forum but leave no evidence of visiting at all. I find it impressive.
As I mention in above post, changing the spark plugs in these cars on a regular basis, and more frequently than other models. Why?
When Ford introduced the 4.6 3 valve modular V8 in the 2005 Mustang, they were also introducing new combustion chamber engineering.
Those engines were built with a longer than usual spark plug so that the spark location was deeper or more central in the combustion chamber as opposed to being on the periphery with a shorter, more conventional plug.
The idea was that the longer plug would contribute to a better, more efficient combustion.
The problem, identified a few years after being introduced, was that if these plugs were left in too long without being loosened or changed out they would seize into the head threads and could break when trying to remove them.
Long was anything above 80000 km as some seized plugs were identified in the 90000 to 100000 km range on F150’s with either the 4.6 or close relative 5.4 V8’s.
For some owners this mileage was achieved in barely more than a couple years.
This is short by today’s standards.
The workaround was not always easy, sometimes requiring a helicoil be threaded into the cylinder head.
To avoid the issue, it was recommended plugs be changed at shorter intervals. Prior to 80000 km and preferably 60000 to 70000 km range, or 4 to 5 years regardless of mileage.
So even if I only average a couple thousand km per year on this car, I have the plugs changed every 5 years as a precautionary measure.
For some owners it may already too late simply because of the age of these cars now.
Meaning some plugs may already be seized and this can’t be established until you try to remove the plugs.
If the maintenance history is not well known to you, then maybe don’t touch if your car is running good.
Consult an experienced Ford tech before removing old plugs who’s maintenance history is not known.
For those of you who do know your maintenance history and wonder if or why you should change plugs in your 2005 to 2010 GT, now you know why it should be done on a regular basis.
I show bellow here for comparison a 4.6L 3 valve plug and a 5.0L Coyote plug.
4.6L long plug.
5.0L more mainstream plug.
