Stripped valve cover thread repair DIY (1998 Honda Civic)
 

Chasing down fluid leaks so I could install a full bellypan (undertray), I stripped-out a valve cover bolt by applying too much torque. I found little step-by-step guidance online for how to use the helicoil, and I have never used one before.

Still, I wanted as close to a perfect OEM repair as I could manage. I think I got it.

The cover is now back on, no leaking, and car running fine. The tricky part is the fact that the head was still on the engine, so drilling out the hole meant aluminum shavings could scatter into the oil.

Tools and supplies:

1 helicoil kit thread repair kit from O'Reillys (M6x1)
1 drill with 1/4 drill bit
1 pin punch thin enough to punch out "tang"
1 ratchet with 8mm socket
Painter's tape (or any tape, really)
paper towels or clean cloth

Pictures

Drill bit, taped to match the bolt's depth:
http://ecomodder.com/forum/attachmen...1&d=1408421362

Helicoil tap, taped to match bolt depth:
http://ecomodder.com/forum/attachmen...1&d=1408421367

Drilling done (forgot to take pictures), here's the tap ready to go in:
http://ecomodder.com/forum/attachmen...1&d=1408421367

Tapping the hole. You see the paper towel tucked in all around the repair area to catch the shavings. I still had to chase down all the bits that escaped:
http://ecomodder.com/forum/attachmen...1&d=1408421367

For both drilling and tapping, I used this copper pipe to judge the perfect angle. I had to go very slowly, and it was a little nerve-wracking when I had to start over once. The pipe is standing snugly on one of the 12mm rocker arm bolt heads:
http://ecomodder.com/forum/attachmen...1&d=1408421367

Here is another shot, showing how nicely aligned the tap came out:
http://ecomodder.com/forum/attachmen...1&d=1408421367

The Honda valve cover bolts are unusual because of the "bulge" that rests on the rocker arm and the fact that the threads are tapered. So if the helicoil insert is to work, you'll have to sink it deeper than generally recommended or the bolt threads will pass it by and then not fit properly:
http://ecomodder.com/forum/attachmen...1&d=1408421367

Knock-out the "tang" ... all along the process I used the tweezers and the valve cover bolt itself, dampened with a little oil, to get the shavings out of the hole. It was slow work, but you cannot blow the shavings out of the hole because they will go everywhere and get into the oil. I let the tang sit in the bottom of the hole, along with some shavings. There was more than enough room:
http://ecomodder.com/forum/attachmen...1&d=1408421367

A perfect OEM fit:
http://ecomodder.com/forum/attachmen...1&d=1408421367

Perfect:
http://ecomodder.com/forum/attachmen...1&d=1408423122

Took just over an hour. :thumbup: