Need suggestions for removal of broken bolt in alloy head

[racer135]

Was removing the thermostat housing from the cylinder head (A12 engine) of my girlfriend's 1978 Datsun 120y and broke one of the bolts off (upper right one) in the alloy head.

Had about 1/4 inch of the bolt sticking out of the bolt hole. Tried to undo it with a pipe wrench (Stillson type) and all it did was strip the threads off and blunt the teeth of the wrench.

Drilled a hole in the bolt (think its a grade 7) and tried an Easy-out (LH threaded type) and stripped the threads off the easy-out and tapered the hole.

Tried the tapered-square type Easy-out, all that did was turn it into a round not-so-easy-out.

Made my own easy-out by bench grinding an old broken Ramset masonry drill bit shank into a square-taper Easy-out. Hit it into the hole in the bolt and broke off the 1/4 inch of bolt sticking out of the bolt hole so now it's level with the head surface.

%%$@%$#@$%#@$#!!!!!!

The hole I drilled in the bolt was off-centre to make things just so much more easy for me hahahahahahaAAAAHAHAHA!!!!!!! (Yep, I've officially fallen over the fence that separates sanity from insanity, into the insanity side!)

I would try somehow to weld a nut onto the piece of bolt in the head, but every time I've tried that welding/nut technique on a broken bolt, the nut always breaks off and makes it harder to extract that last piece of bolt left in the hole.

I'm too hobo to afford a tungsten porting burr for my die grinder, and don't have the time/patience to grind out the bolt to it's threads (what's the easiest way to get those threads out if I end up doing it this way?)

Could try (dangerously) heating the alloy with an oxy acetylene torch to expand the hole, but I think the alloy would heat up slower than the bolt.

Any ideas folks?

 

[Fox Fabrication]

Ahhhh the ol' dissimular metals syndrom!!! 99 out of 100 times when this happens you will need to just drill out and re-tap/thread the hole. I'd just drill it out and get a HELI-COIL kit so you can still use the same diameter bolt that is used in the thermo housing. If you just re-tap it to the next larger size...you may not be able to get that size bolt "thru" the thermo housing. Good luck

 

[R Pope]

Find a good gas axe man! The aluminum alloy won't cut with a torch, the bolt will blow out. Use the smallest tip available, and go for it. Chase the hole with a tap, and you're done! If there's damage to the threads from all the failed attempts, the Helicoil will work good. I just did the same thing on an old Edelbrock intake, but in this case there was threads deeper down, just needed a longer bolt.

 

[dogpatch1]

ive always had luck welding the nut to the top portion of the stud sticking out, letting it cool completely, then with a hammer (and or drift punch id needed for clearence bang on the intake itself all around the threaded area, this distorts the intake and will help in loosening the clamp it has on the stud, slowly tighten the nut, yes tighten it 1/8th turn then start working it back ab=nd forth till it comes out, make sure when your welding that you get good penitration, so the nut doesnt just twist off, also since you have drilled into the stud, brazing a nut to it might work by doing 2 things filling the hole you drilled with braze giving you more nut to bolt adhesion, and the heating process might also aid in loosening the stud from the intake, used to do exhaust and hated broken studs so i feel your pain here., goodluck post what you do to finally get that sucker out, dp1

 

[jfg455]

Usually the heat from welding will help break the hold. Let it get cool enough so you cant see any red anymore. We do it all the time at work on broken exhaust studs