The Stovebolt Site Forums The Shop Area Engine Shop 283 balancer bolt

Hi All,
As many of you know the early, small journal, sbc cranks did not have a balancer bolt. They relied on an interference fit to retain the balancer. I have never been comfortable with this and even Chevy started putting in the balancer bolt in the late 60's. My question is, has anyone ever drilled the end of the crank and threaded the hole for a balancer bolt? I know I could take the crank out and drill it on the lathe but that is a lot of work. If it has been done by hand, and works, that would be my choice of ways to do it. Has anyone done it this way?
Rick

I've drilled & tapped several cranks, and while it's possible to do it freehand, there's a lot of chances to screw up. I'd suggest making up a bushing that slips into the hole in the balancer and centers the drill bit. A piece of air-hardening drill rod machined to the proper dimensions, then torch-heated to straw color and allowed to air cool will become hard enough to prevent erosion by the drill bit, and can be used numerous times. Another one, machined to a few thousandths over the major diameter of the thread, can be used to guide the tap for the first few turns to prevent a crooked thread. The standard balancer bolt is a Grade 8, 7/16X20 thread.
Jerry

It's nearly impossible for one person to drill a hole perpendicular to a surface, but it can be done with two people.

The guy doing the drilling is looking straight down watching that the bit is perpendicular left and right. The helper sits to the left (or right) with his hand on the drill making sure the drill is perpendicular to the crank up and down.

That's how mine was done and it's square to the crank.

Besides, the balancer stayed on the crank all this time, chances are it's not going to fly off any time soon... if you like taking chances with such things.

I lost a balancer once. And I do mean lost, I never found it. One dark night going too fast on a winding road I heard some noise and hit a bump and thought I'd hit something in the road. Almost 30 years later I suspect I hit the balancer.

At the time I had a poor man's drill press, a plastic fixture something like a funnel with a metal shaft through the center so it could mount a chuck on the inside (it was a commercial product my grandfather had purchased). I used it to drill the crank.

Then I spun a bearing. That one was nothing but trouble.

Thanks everyone for your thoughts. Jerry, I really like your idea of making a bushing. I have a piece of 2" round that I can bore part way, so it will fit over the snout of the crankshaft and while it is centered in the lathe, drill the tap drill hole size dead in the center. This I can use as a guide by slipping it over the end of the crank and running the tap drill throught the front hole. If I was going to do more that one I could press a drill bushing in place, but for one crank, I think I will skip the hardening process or the drill bushing. Once the hole is drilled, I can put the fixture back in the lathe, drill out the major diameter size and use it to guide the tap. Excellent, it is great to have you all to ask.
Rick