MTFCA Forum

One of the water outlet threads in my cylinder head is stripped. Any suggestions? it is the thread on the drivers side. Is there enough material around the bolt hole to simply drill it out and re-tap it one size larger? I would prefer not to have to replace the head, but if that's what needs to be done \, I guess I will

Helicoil has worked great for me

Helicoil or threadsert. You may need to remove the radiator to be able to squarely drill out the damaged hole.

Hope this helps.
Allan from down under.

Agree, helicoil.

Helicoil is a "spring" type insert, open between the "threads". Thread-sert is a solid bushing, and while more expensive, will make a permanent repair. Be sure to visit their website to see which length of insert you require. Read their installation instructions to properly measure the depth of the hole (relative to length of insert). Also, you will need loctite #266, red high-strength threadlocker for high-temp applications (regular red loctite will only withstand 200 degree temps).

Greg

Please realize that you can get Helicoil in pipe thread sizes and I have used them with total success to fix T spark plug threads and many other applications

If I were doing the job again, I would remove the head and place it vertically a mill or drill press whether I used helicoil or solid insert. Use the chuck to hold the tap perpendicular after drilling the hole. It is darn hard to get a perpendicular hole and thread using a portable drill and taping without a guide.

First time I did just that and the new threaded hole was not aligned, close but not good enough. In time the repair failed and broke off the ear . I had a pro weld up a new ear and drill and tap it using the outlet as a guide. Live and learn.

The beauty of threadserts is the tap used to fit the insert into the drilled out hole is one of the standard sizes in everyday use. There is no need to invest in any special sized tools to fit them like there is with some/all? helicoils. This clumsy workman has had difficulties with helicoils in other than blind holes like T model head water outlets and front axles, having them continue to wind through when the bolts are introduced. The threadsert are Klutz proof!

Allan from down under.

There isn't much material around the holes in the water outlet where the bolts go. I would use a helicoil in that application as not as much of the original material needs to be removed. I install helicoils with red loctite and let it harden for about an hour so they won't move.

How do you keep the red loctote from bleeding through?

John, threadserts come in a range of external sizes, while having the same internal size, so that a bare minimum amount can be removed if applicable. I had a 1913 block where the head bolt holes had been drilled out and threaded to 1/2" studs. In this application thicker walled threadserts were fitted to fill the oversize hole and at the same time reduce the thread back to the standard 7/16". This makes them more widely useful.

Allan from down under.

No need to use any loctite or adhesive when using Helicoil inserts. Make sure the proper drill is used along with a proper STI tap. Clean out the chips. The insert should be installed 1/2 turn below the top surface. Break the tang off and your good to go. The insert needs to remain flexible. Used to work for Helicoil in another life...

rgould1910 wrote: ↑

Fri Jan 15, 2021 9:47 am

How do you keep the red loctote from bleeding through?

I use very little and apply using a small stick or wire.

My mistake, "Threadserts" are called Time-sert. timesert.com

Greg, thanks for the tip re the name. The brand I have used are actually called Keyserts, but I had never heard of that brand being mentioned in US application.

Allan from down under.

Unless it is some rare, early head. Why not just replace the head??? They are readily available and cheap. Here they charge about $20 to surface one. Find one with good spark plug threads, good outlet threads, put it on and go driving.