One of my spark plugs was found to be cross threaded such that the witness mark from the plug gasket shows an incomplete circle. I bought a save-a-thread type insert kit and installed it, but the insert came back out with the plug when I loosened it as a test. It appears that the swaging tool bottoms out on the insert before the insert is spread far enough to really bite, probably due to the cross-threading ovalling the top of the plug hole. When the plug is tightened down, the insert’s top edge is wedging against the plug, and that friction is what causes the insert to stay with the plug instead of the head.

I wonder whether installing the insert a little deeper, just below flush, and perhaps using a different tool to swage or stake the insert would make it stick.

I have read of other options, the most extreme being replacing or welding the head. Any idea how much these options typically cost? I’m open to trying a bigger insert, or a different style of insert, if the cost is reasonable relative to head replacement.

1964 convertible - 110hp - Powerglide- 3.55 axle - central NC

If you are confident and can drill straight, I think most repairs are to drill and tap to a larger size and use either a helicoil or a timesert to restore the threads down to what they were. Helicoil is just a spring basically and would do fine with spark plugs as they do not get tightened down a lot. Timesert is spendy and you use a full thread steel insert that similar to you already tried that has a tool that expands the insert a bit.

Or you could try the quick route and just use some red loctite to hold the insert in place.

64 Spyder
04 Jag XJR
04 Cadillac SRX
05 Grand Cherokee 5.7

Good ole Minnesota

I'm not sure what thread insert you've tried.
A Time-Sert has a stepped tap that starts out with the 14 mm thread and then expands to to whatever the OD of the Time-Sert inserts is. Then there's a tool that installs the insert and then expands it to lock it into place.
If you've tried an insert that makes the hole bigger but it has failed your choice of what to do next may be difficult. There is a second try Time-Sert. I have the regular one and go to my local Machine Shop for the bigger one.
It's hard to say what you should do without knowing what you used and how big the hole is now. Hopefully the hole is not crooked.

Jim Brandberg
Isanti, MN
CorvairRepair.com

I had an 2 inserts that came out with the plug, used loctite 2620 for high heat.
About 20000 miles later and it stays in the head when pulling plugs

John Oostdyk
Thornhill, Ont
63 Rampy
65 Greenbrier
64 Convertible

I used a time sert for a spark plug, it worked great no problems.
Got the time sert from Clarks, used there tool to install and sent them back to them.
You will have alum chips in cylinder, that you will need to remove.

Dean
Cedar Rapids, IA

64 Monza Coupe
69 500 Coupe
67 Jaguar XKE FHC

Go with the high temp loctite. Don't cover the entire insert, just a drop here and there so you don't reduce heat travel. If that doesn't work, then it time to consider other options

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2023 KIA K5 GT/GT1 turbo-AKA ZIPPY II (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

The old save-a-thread type is the only type I have used in 40 years.

They can even be used on the side of the road with normal spark plug socket.

Grease the tap, screw it into the hole, remove, turn over (start) engine to blow out aluminum that did not stick in the grease, clean grease from hole, put insert on plug, apply Lock-Tite, screw plug in, remove plug, install gasket, reinstall plug, drive on!

What can go wrong?

It needs to be a 1/2" insert.

The insert can come out with the plug. I have removed the insert, put on new plug and screwed them back in. This is when they were daily drivers, so many many miles on them that came back out.

Now having said that, the OP mentions a swaging tool. None in the old save-a-thread kits, hmmm. Oh great, they redesigned the simple kit, of course. Now it has another tool in the kit. The old kit just had a tap. This rod must be the swaging tool.

When I run out of 1/2" inserts I guess I will see what a Time Sert is.

So, Peeeot, does the gasket show proper contact now? If so, I wouldn't worry about the insert coming out with the plug. More Lock-Tite as stated above and drive on. Just do not get it on the plug threads! As always a caveat: But I'm not there to see in person.

Frank DuVal

Fredericksburg, VA

The kit I used is OEM Tools part number 25647. It uses the same type of insert as Clark's Option B, with a couple of knurled threads at the top that are intended to engage with the surrounding metal. The tap starts with M14x1,25 and steps up to a larger size to accommodate the insert.

The plug, when snugged up in the insert, seats completely square like it should. What I'm not comfortable with is that I can only get 5-10 ft-lbs torque on the plug before something starts giving in some way (by which I mean, the torque value doesn't continue to increase as rotation continues). I am not sure whether the insert will pull the threads out if I keep going. As soon as I was sure that torque had plateaued I backed the plug out and brought the insert with it.

The insert feels looser in the threads than I think it ought to until it is at least halfway down in the hole. I suspect that the cross-threading ground away some metal near the top that the tap can't add back.

What about using JB weld high-heat instead of loctite? Apparently Calvan Tools recommends applying it to the external threads on some of their plug insert kits. Copied from elsewhere: "JBW8297 J B Weld High Heat Epoxy Putty Stick, for Manifolds, Tail Pipes, Mufflers and Other High Temperature Projects. Recommended by Calvan Tools for exterior threads of their spark plug inserts to seal and hold securely in place. Commonly used with Calvan 38900 and 39300 spark plug thread repair kits. Made in the USA."

1964 convertible - 110hp - Powerglide- 3.55 axle - central NC

I used a spark plug thread repair kit on a Ford Triton 2 valve engine and you were instructed to use JB weld to lock the steel insert into the aluminum head.

RJ tools
Salem,Oregon




Edited 1 time(s). Last edit at 03/05/2023 04:00PM by 1966-Corsa-GT-180.

I tried the JB Weld solution. I used the original product that comes in 2 tubes, supposedly good for 500 degrees continuous and spikes of 600. I applied a layer to the threads in the head and on the insert (external), then screwed the insert in, ensuring that there was no excess on the combustion chamber side. After it had cured undisturbed for several days I used the swage tool and tapped on the insert a bit, but not very hard because I didn't want to hammer through the epoxy. I torqued the plug to 12.5 ft-lbs and did not try to remove it. Felt solid and plug is square to the seat like it should be. Time will tell how well it holds up when I start driving!

1964 convertible - 110hp - Powerglide- 3.55 axle - central NC