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In working on my 53 AD for 35+ years, I made one of my top-5 bonehead moves and sheared off one of the bolts attaching the water pump to the block (216). Attempted to drill it and tap it (against advice of most posts here, I might note). Now I have sort of a mess: a hole which is a little out-of-round, but still features some of the old bolt left in it. Yikes. These bolts go into a little metal-enclosed indentation in the block, not too much larger than the bolt hole, so I am nervous about drilling it larger and retapping it. I can get this to a local shop and have them deal with it, but wondered what you guys think.


Thanks

PM

I've been lucky to back off bolts that I've broken off by using a small center punch and machine hammer and working the broken bolt back around and out. A Chevy dealer mechanic showed me this procedure back in 1967 on valve cover bolts that I had broken off. This might help you get the broken piece out.

try an easy out, they work once in a while. Use the punch method described above. heat might help, just be careful. Get a set of left handed drill bits, often the broken piece just unthreads. (probably too late now for this problem, just good info for later) you will probably end up going to the machine shop for this though...

At this point I would go get a Heli-coil set in 3/8-16 thread.

Try and get all of the old bolt out with a set of picks you can get them at an FLAPS.

If that does not work ,mount the water pump back on the engine and use the hole as a guild to drill the hole for the heli-coil,in the set it will tell you what size bit to use.Go slow with the bit thru the hole in the water pump it will keep the bit striaght.That should clean out the hole than tap with the tap in the kit install the heli-coil and you should be good to go.


Pete

I know it's a pain. I think we've all had snap-off experience!
The pick idea has worked for me a few times when I drill the hole to the point that I can see the hole threads. Be careful not to drill the threads out.
If you can pick the thin walled remnant away and grab a hold with some needle-nose you could colapse the remnant more and unscrew it out the rest of the way.
You might hand tap in the hole afterwards to chase the threads.
There are a lot of experienced ideas shared here. I like that!
Jerry

Is the hole off-centered far enough to damage the threads yet? If so, it's going to require some heroic measures to correct. You might try bolting an old pump housing onto the block and using the hole in the pump as a drill guide to try to remove the rest of the bolt. That's not likely to succeed, as the drill bit will probably try to follow the hole that's already there and just hog out the pump housing. If I had the block at my shop, I'd use the water pump gasket as a pattern to make a 1/2" steel plate with the pump bolt pattern drilled into it, and open up the hole in question big enough to accept a hardened steel drill guide bushing. This is bolted onto the block and used as a guide to drill out the remainder of the bolt, and then heli-coil the hole. This procedure would involve about $200.00 worth of fabrication work! It's a lot simpler to get a pilot hole exactly on center in the broken-off bolt and avoid the off-center problem in the first place.
Jerry

I like the idea of using the pump to locate the hole, I'd fill the off center bit with JB to realign the pilot hole first I think.

When you get the repair done, you might want to use a stud there. A stud is less stressful on those threads and you could use thread locker to hold it in place.

Since you have the pump for a guide you could use an end mill. It doesn't make any difference where the old hole is located, it will bore straight in without walking. I'd try a 5/16 wrapped with shim stock to hold it centered in the pump hole. This should let you collapse and remove any remaining bolt. If not use a new sharp high quality 3/8-16 tap and thread into the hole cutting away the old bolt as you make new threads. If the hole is so far off to the side that the 5/16 end mill doesn't make a round hole a tap will hang where the notch is. This means one goes with with a 3/8 end mill, remove pump, drill 3/8 hole with drill supplied with heli-coil kit, thread with heli-coil tap, insert coil, and it will then be the strongest thread in the block. You can get end mills at machine tool supply places and will probably need a 1/2" drill motor to chuck them up. Regular ones are under $20 and long ones are still reasonable. I save ones from the Brigeport that have only one flute chipped just for jobs like this.

Thanks for all the ideas! I will update the thread when I resolve this.

PM

Well, somehow I was able to "Use The Force" (Skywalker Force, not the 1/2 inch ratchet kind I used to shear off this baby), and when I mounted the water pump, the bolt magically did track the threads we had cut in. Before mounting the pump, it didn't seem like there was a chance. Very slightly crooked, but workable and tightened fine. Pump in, no leaks, on the road.

Thanks to all for the inputs.

PM