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Robert is correct with what he listed. I do remember wrapping a piece of masking tape around my drill bit to mark my depth, when the tape got to the crank snout I was deep enough based on my measurements.
I went into Amazon and found where I purchased that tap, took all of 30 seconds.
The Tap shows the required drill bit right on the Tap you can read it in the add. 27/64. I bought a new drill bit just because I wanted a very fast clean cut. I did not have to use that much pressure, it cut really well.
The crank is surface hardened but the center is not that hard.
Sgorman3 it's going to be pretty difficult to drill and tap in the car. Mark did his standing up in the garage. its going to be hard to keep straight and to tap, warning Mark typed 27/64 I'm sure he meant 25/64 do not drill it to 27/64. Keep in mind back in the day GM mechanics were pounding on dampers in every vehicle they did warranty work on Vettes, Impalas, station wagons anything that didn't have the bolt hole tapped and more than likely any that did. Worse case you remove the radiator pound it on and be done.
This is is how I do them easy if you happen to have a lathe laying around.
As for the process, I always use a thin 1/8" thick ribbon of RTV all the way around the crank snout (towards the front end of the snout, just in front and over the key), instead of the light coating of oil.
The RTV does a couple of things, including adding some lubricity to pulling on the balancer, while it is still semi-liquid.
But when it hardens, it also seals the path that any oil could migrate down the keyway.
It also (somewhat) prevents the balancer from loosening.
However, it is still easy to pull the balancer back off, using the correct tool.
Note that when reinstalling the balancer that is retained by a bolt, do not use the bolt to reinstall it!
If a bolt is used, it is very possible to pull the threads out of the crank.
Always use an install tool that is threaded all the way to the bottom of the crank threads, and then a larger washer & nut is used to pull the balancer on.
Once it is fully seated, loosen the nut, remove the threaded install tool, and install the large washer & bolt.
I have never had an issue pressing one on using the Bolt method but I do not use the actual bolt, you have to buy a longer bolt or two to avoid stripping things, and if you are buying something might as well buy the proper install tool.
I make sure my extended bolt is at least 1/2" threaded down into the crank before it starts pressing the HB on. When this bottoms out I switch to a shorter Bolt, maybe 1/2" shorter than the long bolt. Press the HB on a little further then finish with the actual OEM bolt.
I have a selection of bolts and washers handy so that is how I do it but a proper tool would be easier and faster.
Here is the tool that I had made for my 57 and the sequence of trill/tap. First picture is of Larry (it almost went through his windshield) and my self after it came off on the highway a few years ago. The original tap drill hole 25/64 (.391) was drilled out to 7/16 for the final tapping.
Thanks for all the help and advice. I was able to tap the end of the crankshaft and used a HB puller/installer to press it on. Took me a few hours but I got it on.
How hard was it to drill the hole with the engine in the car? Nice work, glad you put this job behind you.
Took me about an hour with my battery powered Ridgid Multi-Tool. It was the only drill I could get into the confined area. Hardest part was making sure the drill bit was straight and the breaks I had to take because my arms started shaking.
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