SBC Harmonic Balancer Race Repair
I started painting the harmonic balancer and found that there is a groove worn where the timing chain cover's oil seal is. The solution is to purchase a thin repair sleeve available at most parts sources that press fits over the surface. It costs about $6 and installs quite easily. It was shorter than I expected but covers the seal area.
400 harmonic balancer with worn oil seal groove. The ridge on the outside identifies it as a 400 harmonic balancer.
I used a long bolt from one of my wheel pullers to install the balancer back on the crankshaft. It happened to have the same bolt thread as the balancer's bolt. You shouldn't use a hammer to install the balancer onto the crankshaft cause you may damage the crankshaft's thrust bearings. I threaded a nut, and put on a small washer and the large balancer's washer onto the wheel puller's bolt. Placed the balancer onto the end of the crankshaft.
Wheel puller bolt on top, installation nut on bottom, small washer and larger washer
I threaded the bolt onto the crankshaft as far as it would go. I then tightened the nut to drive the balancer onto the crankshaft. Doing it this way prevents stripping of the crankshaft threads. The bolt is firmly threaded into the crankshaft and the nut is taking all the force across its complete threads. Adding some WD40 to the threads helps.
400's Unique Woodruff key
The 400's crank uses a unique woodruff key from all other SBCs. This is the metal key that keeps the harmonic balancer from spinning on the end of the crank. It is slightly larger than the standard 350 key. After some searching around, I found that I had to go to the local GM dealer. The GM part number is #8E73 106751 and the cost is $1.00.
The funny thing about this part is that the dealer has to order 80 keys at a time. There was only one dealer in town who had the part in stock and that's in a city of close to 1 million people. When the partsmen looked up the history, he found that he had sold 15 keys over the past 10 years since he last ordered them. I bought an extra one just in case I misplaced one.