Spark plug thread repair

[DavidBarkey]

Spark plug repair thread repair kits . Any of you guys had problems with spark plug repair kits not holding due to very short thread contact of the spark plug . My 222 with .10" over and decked head blew the spark plug out because the guy I got it back from thought him self a mechanic and cross threaded the plug so many time trying to put a new one in that there was no treads left to hold the plug . 3 times I tolk the head off and put and insert in "made for aluminum heads " The problem is is that the ID of the insert is 14m 1.25 thread and the OD is 16m 1.25 which only gives 1 mm or .039"wall thickness to provide both the inside thread and the outside thread. Looking though my dies I found an 18m 1.5 . So ordered the matching tap and a 14m 1.25 tap . Now armed with this and some 4140 plate Aluminum from lost and found stash . Hole saw to cut out a blank that was machined to suit . Drilled head spark plug hole out with 5/8" drill bit the "walk" of the drill bit was enough to give me the .650" needed and tapped with 18m 1.5 tap . After the new insert was tapped and threaded on the out side D. A little high temp loc-tite and peening the thread with center punch both top and bottom to make sure it would never work its way in or out I have a super strong repair. That the washer will actually seal properly against . Obviously this story comes to you from before I had a head on with the tractor hood . Hope this help someone else out some time .

Dave

[Eugen]

Dave, having gone through this with an old car I have the tap and even thread inserts. Wish you said something. When I did it on my old crown vic and it held for several years then I sold the car. It was longer thread section though. I used jb weld between the insert and the head.

[ssmewing]

Used heads are dirt cheap and you have to ask someone to sell one as they usually are not worth selling.

[DavidBarkey]

Used heads are dirt cheap and you have to ask someone to sell one as they usually are not worth selling.

I looked a couple of heads in the area and all had the mangle plug threads . Must have been the same guy working on them all Thats why I desided to fix mine , plus I have the mill and lathe to do it with .

Dave

[Eugen]

@ssmewing not plentiful or dirt cheap around here. My k321 was pretty warped and thought why don't I save some elbow grease and just get another head from ebay. All heads I could find were from the US, and not dirt cheap. Add the high shipping price and possibly brokerage charges and it makes no sense to get another head if you can fix it.

The other aspect is that you save a piece of metal from going to the scrap heap, which feels good.

keep on those wheels everyone!

P.S. You guys have it easier than

[DavidBarkey]

The other thing this alows me to do is repair rarer hard to find heads for people and at a reasonable price and make a couple bucks for me . And like Eugen said , that satisfaction of keeping another piece from the smelter . There is only so much of the old stuff left.

Dave