spark plug timesert

[MatMan]

Hello. I am having trouble and need a bit of guidance. I have searched, so please keep flaming and pointing to the search button to a minimum.

 

I discovered a couple days ago that either a PO or a car "tech" did a sneaky, dastardly deed by hiding a stripped spark plug hole in the aluminum head of my Toy Tundra, 4.7 V8. In the interest of being thorough, this post will be lengthy.

 

The plug I pulled out had a green negative electrode, and scale all around the circumference of the firing ring, and in one spot, the treads were gnarled with the same scale. Nasty pic #1 Nasty pic #2 All of the other 7 had tan electrodes with no scale at all.

 

The spark plugs are 14X1.25, so first, I tried to run a 14mm spark plug thread chaser into the hole, but it never seated (never got tight). When I tried to install the new plug, it just fell into the hole, and pulled right out. Stripped completely. I am assuming the scale on the threads was the culprit here.

 

I procured a number 14 spark plug insert kit from the local NAPA which includes a tap and various lengths of inserts. Looks like this one. The directions read that one taps out the head, coats the spark plug with "oil", threads the appropriate insert onto the plug, coats the outer threads of the insert with the included adhesive, and just reinstall the plug to the seat.

 

My problem: the tap will go into the hole, but try as I might, including standing on a ladder, with near all my weight on the ratchet, the tap will not cut new threads. I have coated the tap with grease to minimize shavings falling into the cylinder, which seems to help. I have pulled a few shards of some kind of black rubberized material, the likes of which I have never seen.

 

Could there already be an insert in there? I don't think so because 1) the new spark plug falls into the hole, all the way to the seat: and 2 the old plug is the same thread size/pitch as the new ones.

 

I see that I have two options, maybe you guys can offer more:

 

1) It occurred to me that maybe the piston is resting right at the top of the cylinder, not allowing the tap to do it's job. I was able to start the motor and shut it down after about 5 or so revolutions, but I wasn't able to get the tap to bite. Could it be that the shut down of the motor always has this particular cylinder at TDC? It's the rear cylinder, pass side. Would just tbumping the starter move the cylinder enough to tap it out?

 

2) At NAPA and ACE I was unable to procure the next size up from 14X1.25 tap, I was hoping to find a 14.5X1.25 or even a 15X1.25, to no avail. Would a 9/16" tap, if I can get it to bite about 1/4" be enough to get the kit's tap to work? The threads of the plugs are about 7/8" deep.

 

I am in a pickle. Auburn Toyota quoted me $3000 for a new head and $1600 to remove/install helicoil/replace my head. During my research, I found that time-serts are a much better answer than the helicoil because the coils are apt to 1) break under high loads and 2) back out the next time I replace the plugs.

 

Thanks in advance.

[MatMan]

Well, since there haven't been any replies, I went and tried to fix it by tapping with the 9/16" tap, and then trying to get the spark plug kit's tap to work. I think that one's a 16mm.

 

After about 5 rounds of 9/16" tap then kit tap, then repeat, the kit tap FINALLY caught and cut some aluminum!!!

 

After what seemed to be an hour of cutting, backing off, and cutting some more, backing all the way out to remove shards and shavings, putting new grease on the tap and repeating, I was able to get the insert with the new plug in!!

 

I am frightened, though, because the insert gave good resistance for about 5 revolutions and then went easy. I REALLY hope I didn't strip the head. I hope the threadlock stuff works.

 

The truck started right up, and I let it idle for about 10 mins, and was able to drive it about 25 feet to make sure the thing didn't blow out the head.

 

Success, I think.