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They are 8x1.25. I read about someone putting in 10mm Toyota studs, which may have been double ended with 8 on the outside end. But that may not be necessary.
Look for info on taking them out with an electric welder. Really. Quick and simple with no damage to head or threads apparently. Someone here posted about it some time ago and I have since read other articles and practitioners. It seems to work even if the stud is broken Below head surface. I have read nothing but good reports about this method, so much so that it's the only thing I am going to try.
I'll try to find something.
This is in the FAQ
Removing Broken Studs With an Electric Welder. [Tip from Gary DeFrancesco] Last spring I removed the head off my '87 745T due to a broken stud. In my case, the stud broke flush with the head, so there was no way to get a wrench on it. Took the head to a head shop and had the machinist replace all the studs, figuring that if one stud is bad, more were ready to let go. The machinist trick to removing the remaining studs was amazingly simple and effective. He hooked up the hot side of his welder to the stud, the ground to the block. Set the welder for about 150 amps., then turned the welder on for 2 seconds. The studs after this treatment are hot to the touch, and the head is a bit warm. But the crud in the threads that makes the stud stick is all burned out. It is the crud that is causing the high electrical resistance. Hence, it is the crud that really heats up and burns off. With the curd burned off, he is able to easily unscrew the stud. He finds better than 90% of stuck studs can be removed this way. And there is no warping of the head since the heat is pretty much contained to the cruddy threads and is only applied briefly. Just one of those welder tricks I have filed away for the day when I get a welder.
Another trick you can use if you have a welder is to select a nut with a hole large enough to pass over the stud. Lay the nut over the stud and then fill the hole with weld metal. Then simply screw the stud out with a wrench. Or butt-weld a piece of welding rod onto the end of the bolt so that you can turn the assembly with pliers. [Jeff Goggin] Using a welder, slowly build up a bead of weld on top of the broken stud, until it clears the surface of the head. Using vice grips, grab the weld and twist out the stud remains. I used an oxymig at the slowest wire feed (basically dropping weld beads onto weld beads), and a medium high setting (110v 30amp welder) - ground clamp to the #1 cam journal. Allowing each bead to cool before adding more material, is the key to getting this right.If the weld breaks before the stud would break free, just keep going at it, rewelding until the stud breaks free. This may take over 6 applications of the weld bead technique. Use a hammer on the top of the bead each time, tempering the bead, which appears to reduce the chances of shearing the bead off the stud.
This procedure negates any need for the drill and helicoil procedure in which the biggest problem is getting a straight hole and not drilling through to the water jacket beneath.
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