Damaged threads to spark....

bluej58 wrote: Do the bad one first and if it goes well you can decide if you want to do the others.
I go by the saying " don't fix what ain't broke"
With a trip coming up why take a chance

Nessism wrote: I would NOT install inserts into all 4 positions. No need unless the threads are damaged now. It's just asking for trouble.

gordone wrote:

Nessism wrote: I would NOT install inserts into all 4 positions. No need unless the threads are damaged now. It's just asking for trouble.

Can I ask why?
The high quality time insert is stronger then original threads?

Irish Yobbo wrote:

gordone wrote:

Nessism wrote: I would NOT install inserts into all 4 positions. No need unless the threads are damaged now. It's just asking for trouble.

Can I ask why?
The high quality time insert is stronger then original threads?

The original metal has plenty of strength to seal the spark plug. There's a fair amount of time, effort, and risk involved in using a timesert, and since it doesn't actually improve anything , it's just not worth it to replace.

The only reason threads are damaged is from over tightening. Provided you don't overtighten the spark plugs, the threads will never wear out. I would inspect the remaining three threads, make sure they're not visibly damaged, and then insert a spark plug and torque it to spec. If it tightens to spec, all is well, no need to create more work.

Patton wrote: The initial threads may be cross-threaded (often resulting from some earlier ham-fisted plug installation) making it impossible to get a plug properly started into the hole.

Often, there's a lot of good undamaged thread remaining deeper inside the hole past the shallower cross-threaded area.

The challenge then becomes how to perfectly re-thread the shallow cross-threads to sync perfectly with the deeper good section.

It may be possible to re-cut the cross-threads by starting at the deep end with a reverse tap, also known as a back tap.

The reverse tap inserts all the way through the spark plug hole, and then the tool's deep end expands to begin tracking along the good threads from the deep end, and re-cuts the cross-threaded section as the tool proceeds upward and out of the hole.

It's akin to having the head off, and re-threading the hole in the normal manner starting with the good threads on the piston side of the plug hole.
A reverse tap accomplishes the same result, but without needing to remove the head.

Here's a pic of the reverse threading tool.

Successful reverse tapping depends on having sufficient remaining thread area inside the sperk plug hole.

Good Fortune!