Just did the repair for this on my 1983 L69. I used the Time Sert instead of the heli Coil. I searched here to see if anyone else had done it and what their experience was. Did not see anything, sorry if this has been covered before. For those that are not familiar, the Time Sert in a threaded bushing. Seems more robust than a Heli Coil. The Time Sert is much more expensive though.
What I found doing the repair.
The hole in the crankshaft is about 1 1/4 deep.
I debated what length Sert to use. They are available in many lengths for the 7/16 -20 size of the bolt.
The kit comes with a 0.6 inch. I used that length. My rational was that there really is not much torque ( 60 ft -lb) on the bolt when installing the harmonic balancer or installing the bolt. If I was running a bolt into a nut, the nut would would be around 0,6 inch, so I thought it would work. It did.

- Drilling the hole. My 1/2 inch Dewalt worked ok. It stalled many times drilling the hole, but we got thru it. I confirmed this with Time Sert, when drilling the hole, it tends to follow the old hole. You have to be careful, but it worked ok for me. I was doing this in the car and removed the electric fan to get more room for the drill. I left the radiator in the car.
- Next step was tapping the hole. Time Sert sells a tap guide the holds the tap square to the hole. That worked very well.
- The next bit is to create a chamfered lip for the Sert. The bit supplied worked very well. It has a lead in to guide the bit.
- The last step is to install the Sert. Again the tool provided worked very well.

I then used the Harmonic Balancer install tool to install the Balancer. Work great, no issue.

The car is now back up and running.

 

I've done it with HeliCoils but never a TimeSert. In the particular cars I was working on, the bolt hole was also accessible, without too much teardown.

Glad you got it handled. That's a really critical place to have a failure.

Might be interesting to know why it was necessary in the first place.

 

Ed Cole saw this coming. 70 years ago he designed this engine, but had no way of knowing that people wouldn't read ALL the notes.

It could be too late for this crank, but if that ever happens again, go back to Eddie's notes and see the bill of material. Observe that he selected a somewhat uncommon 7/16-20 bolt for the crank snout. He knew that if people didn't read the notes and used improper techniques to mount the balancer, this could happen. The note following the instructions indicated that if/when this happened, a much more common 1/2-20 bolt could be installed after carefully re-tapping the hole. No insert needed.

 

BTW - That's an interesting username. Pretty close to one I have:

 

I had the harmonic balancer off a number of times in the late 1980's. The timing mark slipped, oil leaks, etc. I must have been borrowing the install tool. For some reason the last time I touched it, did not use the install tool and used a variety of different length bolts to install it. Operator error. Fast forward to now. The crank seal was leaking and wanted to replace it. The threads failed about half way into the harmonic balancer installation with the install tool I now own.

 

Vader, The Darth 93 .....I have 2 Saab 93s. One is black. I was using the same name across multiple web sites. May the Force be with you!

 

I have never had a problem using bolts to install an SBC damper- several dozen-over the last ~40yrs and not even buggered threads...needs to be pulled all the way up so sprocket is tight.You may know about it ,but there is a big Saab museum near me in Sturgis SD-92s up to the last.I had a '71 99 for about 20yrs Earliest SBC dampers were just pressed on.

 

That's partly because they weren't really "dampers". They had no rubber, no inertia ring. They were basically just a flange for the pulleys. It was possible to put a bolt in them, using the "puller" (excuse the impossible-to-avoid pun) threads; but no application-specific bolts existed yet. Earliest "dampers" I can recall for SBC were on some of the 327s and in cars w AC. I'm not sure that 283s ever came with them butt memory is hazy from back then.

 

Great write-up (with blind hole depth) and "planning ahead" historical note by engineers.

Was the tap guide from Time-Sert jist over 1/2" i.d.? What did it set in / against?