Are there any measurements or visual signs to know when the vibration damper is properly seated on the crank? I just remounted mine on my stock 71 SB using the crank bolt and a breaker bar. It slipped on the crank pretty easy, but how do I know when it is all the way on? I think it bottomed out but I was surprised to see that there is about 1" remaining on the inside of the balancer hub. Is there supposed to be that much remaining? I also noted the back of the hub is about 1/2 inch from the timing chain cover.

John

 

There are so many possible references and level of accuracy that you could be using that its hard to say, but the 1/2" at the timing cover doesn't sound too far out of whack. Mine appears to be maybe 3/8"-1/2" to the seal along the crankshaft nose.

John, there is a special tool that is absolutely worthless for anything but removing and installing vibration dampers. You can buy one, rent one, borrow one, or steal one, but they are indispensible for removing and installing vibration dampers. Considering what can happen when a damper is improperly removed or installed, they are an excellent investment. There is no way I would remove/install a damper without one.

It sounds like you are OK, but I will tell you what I do when something like this happens and I don't understand the result...remove the damper WITH THE TOOL, inspect it carefully for internal stops in the bore (measure them) or burrs inside the bore or on the nose, and re-install the damper USING THE TOOL with the nose lightly lubricated.

 

Thanks Chuck. I thought about the tool, but opted to take my chances with the bolt. I did all the other things you suggested prior to installing. It slipped on very easy and I think it is there. I was just surprised to see about 1" of the inside of the hub extending out past the end of the crank and was looking for some reasurrance.

 

If you are sure you have stock pulleys, see if your fan belt lines up.

 

An inch of "freeboard" remaining inside the hub does seem like a lot (can't see mine, it's covered up).

It's been a long time since I replaced my vibration damper, but vaguely I think I remember going through this exact same anxiety even to the inspection process I described. But, one thing is for sure...you can't use up ALL the "freeboard" inside the hub or you would be into the timing cover. So, there was always going to be some space remaining in the hub.

There has to be a step in the bore, a positive stop, that prevents the damper from going any further up on the nose than it was designed. If you have identified the stop, measured the distance from the stop to the rear of the hub, and then measured that distance from the end of the crankshaft nose and are left with a half inch or less that will remain between the hub and the timing cover, then I wouldn't worry about it any more. It is full up. Don't forget to torque the center bolt to specified torque. :D

 

There is no stop in the bore. I believe the "stop" is when the end of the hub bottoms on the timing chain crank gear. Unfortunately, I failed to measure the length of the hub and distance from outside cover to crank gear before installing the damper :(

 

Hmmmmm...OK, you motor gurus can step up any time here. :D

Nope. That can't be true. You are essentially saying there is no stop; that the damper is free to move back into the timing cover, seal, and gear. That would be big-time maintenance problems and GM engineers would never design it that way.

As I remember, the keyway is broached all the way through the damper hub bore. However, on the crankshaft nose, the keyway is broached to the specified length where the tool was withdrawn leaving a radius in the end of the keyway.

If there isn't a physical stop, then the only other thing I can think of is that the vibration damper is intended to go onto the shaft end until the key "bottoms" at the start of the shaft keyway radius...then, the key will wedge in the keyway between the hub and the shaft. The damper will go no further unless the key slips in the damper keyway, which is unlikely because of the friction created by the wedging action, or alternately, unless something is deformed (not a good option). This is not a real precise way to locate machinery parts, but effective if the tolerances are measured in sixteenths of an inch which is probably true in this case.

The thing about using the remover/installer tool is that each removal/installation is not like a moonshot where you cross your fingers, and hope everything goes OK. Removal or installation of the damper becomes no big deal.


[Modified by Chuck Sangerhausen, 12:02 PM 9/3/2002]

 

There's no stop, and no wedging action - both the bore and the keyway are broached all the way through the hub; the rear of the hub bottoms out on the crank timing gear (or the 1/8" spacer on a C1). Not a good idea to pull it on by turning the balancer bolt - if you strip the 7/16"-20 threads in the crank snout, that will ruin your whole day. Use the correct tool, or use a length of 7/16"-20 threaded rod, threaded all the way into the crank, then use a nut and greased washers to pull the balancer on - when you can't tighten the nut any more, it's bottomed out, then remove the threaded rod and install the bolt and thick washer with some Loctite.

 

Thanks for getting us (me) straight, JohnZ. John was right about the damper bottoming out on the timing gear, and he does seem to have a problem.

I had forgotten that the damper hub actually goes up into the timing cover seal, and that the reason the timing chain seal doesn't seal is because the damper hub OD is worn and has to be sleeved. Duh, I'll just stfu now. :D

 

I like John Z's suggestion on using the threaded rod. Chuck, you are correct on the seal wearing a groove in the hub. The seal kit now days comes with a sleeve to correct that problem.