Go easy with the heat. Using the head, Make a sleeve to slip into the bolt hole with a 1/32",smaller than tap drill size ID. Go easy with the drill and kinda pick at the stuck bolt. Blow out the hole often. Then go back a reamer that is tap drill size, use cutting oil-not wd40, and go slow. If the stuck bolt starts to move stop there. Then you'll have to pick the bits out of the hole with a scriber? If using a Dremel tool, either stones or carbide burrs will get it done with patience. Chasing the threads with a standard tap is incorrect. The GH3 type tap will cut deeper, sharper threads than the original ones. Use a correct thread chasing tool meant for those headbolts.
Word to the wise when working on stuck bolts. Don't just go at it with a big wrench and try to unscrew it. You have to treat it like a lady. Start out with your average wrench size, bigger is not always better. a little warmth and plenty of lubricant. Work on screwing it both ways, in and out. Keep working on it slowly, in and out in and out. Before long, you will start making some headway, you will feel it start moving. Soon you will be making bigger turns at it. A little more lube and you feel it move farther, farther and farther. And before you know, it will *** flying right out of there with a great sigh of relief. And clean your dirty nuts
The best thing to do with those spiral tapered EZ Outs is to gather up every one that you have in your toolbox, lay them on your welding table, line them up, and then weld a very thick piece of s**** steel across the bunch, making sure you use more heat than necessary. Flip the whole ***embly over and weld another piece of s**** across the other side of them. Then throw them into your pile of stuff headed for the salvage yard. Nice.
Experience is what you get when you get what you didn't want. In my opinion, based on years of experience, you should NEVER try an EZ Out of any kind on a bolt that twisted off while you were trying to remove it. Why? Because, first off, you will never be able to equal the torque that the full size fastener withstood before twisting off with an EZ Out. Second, an EZ Out is tapered and when you twist or drive it into the stuck fastener, it just tightens the grip of the threads. What you end up with is a broken off EZ out, which is hardened and are even harder to remove. Again, Do Not use EZ Outs on a fastener that twisted off as you were trying to remove it. You are just setting yourself up for more work. They work fine for a fastener that failed in shear but that's about it. If this block belonged to me and I was serious about saving it, I would strip it and take it to a machine shop. I have used some of the various other suggested attempts before, with varying degrees of success but NEVER in an engine block. YMMV.
First of all drills are not made the cut with the sides of the flutes. You are probably not going to be able to make an out of round, round with a drill. The hole already looks too far out of round to be saved with Heli-Coil even if you could drill an oversized hole. I think the only hope is stripping the engine down and sitting the block on a mill, a Bridgeport might work. Then plunge cut the hole with an end mill, preferably precision located to the head bolt pattern. Then either purchase or manufacture a threaded insert. Tap the hole in the block to what ever the outside diameter thread of the treaded/manufactured insert is. If precision located you could also drill/tap the insert to the head bolt size. Screw insert into block with tread locker (Loc***e) it doesn’t have to be gorilla tightened. The oversized insert will prevent it from turning out on future head bolt removal. This is probably going to get expensive unless you have a friend with a mill. Anything less than this will be a compromised thread that may not hold torque and lead to blown head gaskets. My opinion your mileage may vary.
I agree that the hole is so far messed up that it will require an end mill to get rid of it. Bite the bullet and strip it down and take it to a machine shop.
And end mill is probably your best bet, but here is another suggestion: Put the blade of a straight screwdriver down into the hole and weld one side of the screwdriver blade to the fat side of whats left of the stud. With enough heat cycles and penetrating oil, you might be able to get the stud to turn with the screwdriver. The key is getting enough weld (heat) onto the stud. Oh, and dont weld the stud to the block. Good luck! Let us know how it goes...
I'm retired now,an have been for 30 years,so know the cost I give was 30 years ago. Yup, this is the type of thing I'd some times get,come in to my shop ,they'ed bring it in already screwed up like that or even more! I fixed a lot of that stuff,with out having to put in a Helicoil,but some had to be done that way too. I had a sign" If you broke it off ?">> Maybe I can fix it! But if you tryed to fix it ,and screwed up more,it will cost you 10X as much!! $$$" If I can't fix it,my work is FREE." Often $100,or plus,for real screwed up,,but fixed. Only as a point ,on what to expect from a shop.
Being a line mechanic since 1977 in the independent automotive shops, there isn't a broken bolt I haven't met.
IIRC there was an article in Hot Rod some time ago about removing broken bolts with a metal disintegration machine. The cost seemed reasonable and I don't think they used a bare block in the article. Edit: Motor Trend not Hot Rod Hot Rod To The Rescue - 1965 Mustang Broken Tap Extraction (motortrend.com)
Since the bolt backed out of the hole a short distance I would try a Dremel with a grinding stone or carbide bit to remove material from the thick section of what's left of the bolt, once the thick part is ground thin use a chisel to collapse the shell of the bolt towards the center of the hole. Another trick is to use a chisel on the very edge of the bolt to try to get the bolt to rotate. Remember, patience and perseverance, let us know how it worked out.
You mentioned a “3/16ths through hole”. I’d tap it and plug it with a 1/4in set screw. That way you can fill it up with you favorite concoction and let it work into the threads and not run out the through hole. It looks like most of it (to my eye) that’s left is below the deck. A MAPP torch probably didn’t get things hot enough. I’ve used them out back on hydraulic fittings, but the nuts are pretty thin. I looked into EDM when I heard about it years ago, but no one in my area had the machine. But if there is one you can get to, as mentioned you won’t have to tear the block down for it. And I hope your shop meant putting he block on the mill, not lathe
It looks to me that you have some of the original bolt still showing. What I do to remove most broken bolts is a series of ***** punches. get behind what is left of the bolt and try to tap the remaining piece towards the center of the hole. Start off with a fine sized ***** punch, and work your way up. At some point you may be able to grab what is left of the bolt with a pair of needle noes pliers. and wiggle the piece / pieces out. I have done this many times. It is time consuming, and a PITA, but it usually works for me.
After looking at the pics close up, it looks like half of the original thread have been drilled out already. Sir, that bolt hole is done. On top of that, this engine does not look like it's ready to run anyway. Tear it down, have the block cleaned and checked for cracks. Have a qualified machinist fix the hole for you.
I’ve got to do the same thing. 2 are broke off flush, one has about 1/4 sticking out. I’ll probably weld a nut to the one sticking out. The other 2 I will probably use the bead as a guide. I’ve done that with water pump housings. Make a sleeve for the housing that fits the drill bit. I think I’d punt on this one and get my machinist to handle it at this point. but probably wouldn’t hurt to try the punch idea suggested. I’ve also had good success with ease outs but if drilled correctly, I’ve rolled threads out like helicoils.
I hear ya. The pic is kinda deceiving. The thread showing is overlapping the hole. If cut straight across the deck, true hole will be exposed. As far as rebuild, I have many questions. The motor was a race motor from the 50s. It's been bored and stroked so I will not be able to just purchase an off the shelf rebuild kit.
I've been watching this and thinking. I've seen a bunch fixed in the shop. Trying to figure an at-home way. Rent/borrow/buy a mag drill. Find a Hougen/Hole Shooter/annular cutter bit big enough to cover the entire aborted effort. Cross reference the size you pick to be the tap drill for some thread. Metric/pipe/whatever (nice if you can find a die to match, or can cut threads on a lathe). So long as you can get a tap to match your hole. I would say solid carbide or carbide spade drill bit might work. The interrupted cut going through the remains of the hole and bolt might get stinky quick. An annular cutter likely would spit that out to the inside. I like them. The ID should be at least as big as the biggest diameter of the problem area. Hog out the lesion. Make the hole big enough to cover the offset and still have meat left for your bolt/stud. It doesn't have to be centered, just big enough. Tap the hole. Tapping cast iron ****s. Use a bolt or make a solid plug and wind it in the hole with bearing lock or super duper loc***e of some sort. Would be nice to saw/file/sand/s****e it flush. Make a pilot or transfer punch to match the hole in the head. Snug the head down and mark/drill your center back home. Drill & tap for a head bolt and Bob's your uncle. A machine shop with the right equipment (and machinist) will do it in a tiny fraction of the time, surface the deck to make it flush, be better and can charge you whatever it would cost to replace it. Pulling the engine and rebuilding it might **** and cost enough to make it worth your while. And it will take a while. I can see it. Mike
I've never heard of a flathead race motor that used custom made bearings, rings and such. The parts you will need are just oversized stock items. Maybe the cam is custom ground. Maybe the bore is larger. But you can find those replacements if needed. Even a stroked crank uses Ford rod bearings. You just need to do some measuring.
Pop head on, and other bolts in. Use head to see how far you are off. From there... flip the coin. One option, Send a tap down if allready pre drillled it, loc,tight and stud it, i dont see a 8-71 blower going on the top, so you could cheat on this. Is it aligned? If your loosing your mind on it, then go to the extent of a 1/4 plate on top of motor, 4x8" 2 or 3 bolts, get a freind with a mag drill, lock it down with, the exact lineup calculated. Install the said bit, hougen, ect, drill it out, slowely, drink some more coffee, Smile, and tap. If your freind has the carbide bits in a diegrinder, and hes talented, he could skim back to thread tips, then tap. A bolted plate, or structure to rest againts, is your freind, they sell 6 inch bits, nice for seeing the angle of the dangle. Its not the end of the world. Sometimes, a metric bolt, is a tad bigger, if you cant stomach heli coils
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