Own a 99F250 SD w/V 10. # 10 cylinder spit a plug last night. This is the second time this has happened. Both times I have been lucky and the threads have not stripped. first time this occurred I removed all plugs and retorqued, can't remember value, but it was something like to 100-120 in*lb. This time torqued to 130.

No other plugs have spit. I find it odd that this is twice on the same cylinder. Coincidence or is there something wrong with this one?

 

Torque is 132 in.-lbs.

 

I would torque them about 30 foot pounds.

It could be that the first time the plug was simply loose. # 10 is the most difficult to reach so it is possible it did not get as tight as the others. Then the 2nd time, there is likely some wear or deformation on the threads due to the first ejection. If it was mine, I would install a Time-Sert on # 10.

 

You are a little short of the factory spec of 132 in/lbs, which in my opinion is not tight enough. I have an '05 2V which has a factory spec of 14 ft/lbs (168 in/lbs) but I torqued them to 32 ft/lbs (384 in/lbs) with just a dab of nickel anti-seize on the threads.


There was a guy online who torque tested some of the 4 thread early motors in a junkyard, he took them up to 110 ft/lbs without any thread failures, so I think upping the torque over the very light factory numbers is safe. (Don't go to extremes though...).

 

The problem is, he didn't subject them to any heat cycles and observe the results

Even 30ft/lbs is a bit much in my opinion.

The rate of thermal expansion of steel is almost half that of aluminum. In the area between the threads and the taper, the head will expand a lot more than the steel spark plug. That means if it's too tight, it WILL either hollow out the taper in the head, or pull the threads.

But yeah, 11-14 ft/lbs is way too loose if you ask me.

 

I agree with Sam I Am statement. Likely that the threads are deformed or otherwise mucked up from the first time it blew out.

Spend the $200 or so to have a Timesert installed and be done with it.

 

I would not use anti seize on the 2v valve engines. the torque specs are based on dry threads. plus with a motor that has a history of plugs backing out why would you want to give the plugs less resistance. I know the 3 valve engines had a problem with plugs breaking off because of the design .

 

Sounds like you need a Timesert in #10. It is highly unlikely the plug backed out enough to blow and not do damage to the threads once, let alone twice.

 

I had a hard time finding a consistent torque spec. I think 30 ftlb is way too high. I will go in and retorque them to 140 inlb. As for the timesert I'll save that for next time. Runs now don't fix what isn't broke. If it pops again I can disable the injector and coil and limp her home then timesert it. Thanks

 

That is why your plugs keep ejecting.