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Stripped Head Stud

It’s called Murphy’s Law and it hit me a in 1996.

 

We moved to a new home with a nice big four car garage. The garage was built out of cement blocks with only one window on the west side. I didn’t think this would be a problem but when winter started to change to spring, the outside air warmed up and the cement blocks stayed cool. This made for a real prob­lem with condensation. The autos were dripping with condensation. Every metal part was sweating even my tools inside the workbench! The dehumidifier I put in the garage did nothing, even the floor was wet like a melting ice rink. It took fans and a few days of nice weather to dry out the garage,

 

Afterwards I opened the bonnet and all I saw was a coating of rust on every metal engine part!

 

The worst thing to get at was the cylinder head dome nuts and washers. The rust was all around the washers, right where you couldn’t get at it. The decision was made to remove the nuts one at a time, clean each one and then retorque each one down before removing another. Everything went well at first, a couple of studs came out with the nuts but that was ok as they torqued back in just fine. The trouble was one stud would not go back in. It would not engage with the threads! I tried turning and turning, tapping it with a hammer, but it would not engage with the threads. There must have been something that dropped down  in the hole where the stud goes. Now it was time to drain the block and make up some kind of light to look down into it. I had some model railroad light bulbs and a transformer which made a nice little light to slip down in the 3/8 inch opening. Sure enough, there was a piece of metal lodged in the threaded opening. To make things worse, I had pressed it tighter in the opening when I was trying to get the stud to engage. It was possible to get a long • picker/grabber tool” on the metal piece but it was too tight to pull out! Finally after bending and grinding a small steel rod, I was able to get the piece loose, then grab it and pull it out. What a great feeling! Now, time to torque’ that last stud down and it’s back on the road.

 

As I was tightening it down the gauge went to about 15 pounds of torque and then slipped! It would not go the 58 pounds that was in the specifications. I left it like that, filled the radiator with water and started the car. Water leaked out from that stud like a river flowing So now what?

 

After calling around a few places and Jaguar people, I was no better off. Many said a new block will have to be installed, others had no idea what to do. I decided on giving Heli-Coil (thread restorer) a try. I have never used them but have heard they work. In order to do that the cylinder head had to come off. One of my favorite jobs that requires removing most of the other engine parts along with the head! After I got the head off the block I noticed the stripped threads were not at the top of the block, they are about 10 inches down inside, at the bottom of the block! The tools for Heli­Coil are only 4 inches long and you can only get to the threads through a 3/8 inch opening, now what? I can’t get down to the stripped threads to fix them! There must be a way…. I don’t want to buy a new block!

 

A friend on mine took the Heli-Coil drill bit, thread tap, insert installer and chucked them in his metal lathe to weld a 10 inch piece of steel rod to each tool. The lathe kept everything perfectly straight during the welding.

 

Now I could get at that the stripped thread. The process involves drilling out the stripped thread, taping it to accept the Heli-Coil insert, which will match the old threads on the stud exactly.

 

It worked like a charm! The extended tools reached down inside the block perfectly. The stud went in so well, I decided to make up a tap for the other studs and clean out the grit from those threads. All of the studs could then be turned down in their threads just by us­ing your fingers.

 

Total repair cost for this job ended up being less than a hundred bucks and quite a few hours in the garage! That’s a lot better than replacing the entire block!

As of 2016 it’s been 20 years since I made this repair, it’s still holding up just fine. Been on plenty of long drives, weekend trips of over a thousand miles and never had a problem.

Fixing a stripped head stud in a Jaguar E type

Bending over the engine and rethreading the drilled out opening for the Heli-Coil.

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