Head bolt heli coil

You might want to take a look at "Time-Serts" They are basically "upscale" heli-coils. A little more work and expense, but they are supposed to be better. With the relatively thin decks on a flathead, it may be a better idea. (This from a guy that heli-coiled a head bolt hole and had no problems with it.)
 
Maybe he meant to type "thread serts" ??? Sort of like a thin tube with threads on the outside and inside. Machine shop supply houses have them. I would probably go with the Heli-coil because the thread serts are thicker and more material will have to be removed from the block to insert them.
 
I did an engine last winter that had 12 block head threads that someone screw up,I installed heli coils. (Write this down in your little book.) The tap drill for the 7/16 heli coil is 29/64 if I remember right, that drill fits the hole on the heads perfect for a drill guide, SO, I bolt a head on the block and drill the bad thread out, NOW. I have a junk 24 stud head I drilled the holes that I needed 35/64 that fits the 7/16 heli tap and makes a nice guide to tap the threads in the block. That makes it easy, it's always hard to get the tap started straight. Walt
 
You might consider a more permanent solution. Drill and tap for a cast iron pipe plug.
Then you can drill and tap for your head bolt size.
Almost invisible and strong.
Bruce
 
Heli coils work well,if you read on Emharts home page you will discover that every 747 that leaves Boeing has 250,000 heli coils installed from the factory. They are a mil "spec" repair.Thread Serts are just another style of thread repair.Stick with an industrial repair and not a home grown job.These repairs work and are very easy to install.Heli Coil even have a system to repair a thread where the heli coil has been damaged and must be made serviceable again.

R
 
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