Bent Valve / Pulled Stud

[RustBucket]

I was driving home from work yesterday and when close to home I accelerated away from a light and rev'd the engine up (tach said about 5500 but it is not trustworthy), a heard something funny then the engine sounded like it was missing. I pushed the clutch and it idled, but rough. I limped the mile home and it sounded like one cylinder was huffing air. Today after work I pulled the rocker cover off and noticed right away that the #1 cylinder exhaust rocker was really loose (valve clearance was 1/4 inch maybe). The intake valve was compressed (open) on the intake stroke. On further inspection I noted that the #1 cylinder rocker tower was loose. The nut that holds it down was loose, but it looked like the normal amount of threads sticking out the end. I pulled the rocker arms/towers assembly off the head and saw that the #1 cylinder rocker tower stud was threaded out about 3/8 inch. In reality I think the cylinder hit the valve and it jacked the rocker arm up and pulled the tower stud out of the head. Is this possible? Is this repairable? It's an aluminum head, R16. Any suggestions on what to do would be appreciated. I haven't pulled the head off yet. In the picture below you can see the exposed threads of the stud in the red box.
Thanks,
Rustbucket

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Edit: I just pulled the stud out. It looks like it has a helicoil or something. I've attached a picture of the stud hole and the stud end with the coil.

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StudHole_small.jpg

[spl310]

The hole is stripped. A helicoil should fix it.

[RustBucket]

Hmm... you are right. I ran a feeler up the inside of the hole and the threads are gone. Should I pull the head and check the valve/piston?
Is the hole a dead end or is there a gallery or something at the end of it?

[Linda]

A thread on torque for rocker studs:
http://www.311s.org/phpBB3/viewtopic.ph ... ocker+stud
Linda

[JT68]

Hole is a dead end. If you are very careful, you can helicoil it in the car. However, if you get off-axis, the head is coming off and a custom threaded insert will be required. Youll need to take precautions to catch the chips. Another example where too much torque is very bad.

[RustBucket]

Following said advice I drilled and tapped and helicoiled the head. It was much easier than expected. M10x1.5 helicoil kit from Autozone or something $30. The head aluminum is very soft. I made a little wood jig to help me get the hole straight and kept a hand held vac to use often. Seemed to work fine and now it runs again!
Rustbucket

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[JT68]

Excellent. Nice job!

[RBMann]

Nice chip collector/cover.

[Linda]

You must be an orthopedic surgeon...that looks very neat.

Linda