Alright guys, I have a 97 z28. It's had this vibration ever since I bought it. It has an under drive crank pulley so I took the balancer off and poof vibration is gone. My question is it necessary to have the balanced on there at all? This is strictly my daily driver, might see the track a couple off times just so I can get an idea of how fast it actually is compared to others. And if I do need to replace the balancer, who would be cheapest? Also if anyone has one for sale shoot me a pm. Thanks. -Kyle

 

It's not a balancer, it's a damper (which means it's neutrally balanced).

If you value your front main bearings you will remove the underdrive pulley and put the damper back on. It's job is to dampen (go figure) crankshaft vibrations. Without it the bearings take the direct beating.

In this case abandon the junk piggyback pulley and run the stock damper alone.

 

The dampner can have a right way to go on; courtesy of SpeedyGonzalez in another thread:

"The balancer is a two-piece assembly with a pulley that bolts onto the hub. Separating the two made it easier to install the Optispark distributor on the assembly line and out in the field. The holes in the hub are offset, so the balancer only fits on it one way, but there’s no keyway in the hub to index the hub on the crank. This shouldn’t be a problem unless the damper was drilled at the factory to "trim" the final engine assembly.

If it was drilled a lot to compensate for an engine that was out of balance, you could end up with a shaker, depending on how everything stacked up with the remanufactured engine compared to the original engine. If you encounter a balance problem on a remanufactured LT1, try rotating the balancer assembly on the crank 90° at a time to see if it eliminates the problem.

I have yet to see one that wasn't "trimmed" by the factory with several holes drilled in it for final balancing.

If it does have a mark in it for TDC, the best place to put that mark is at either 1 or 6 TDC to start. Then work from there.

I guess I don't need to say that when you remove things in the future, mark them for reference."

So find tdc with a wheel and plug stop and make sure the dampner is on correctly. From personal experience, it also makes it impossible to adjust lash if you put it on wrong.

 

Did you check the damper for damage to the hard rubber ring that connects the inner and outer halves of the damper?

 

It's definitely shot, I can turn the outer half by hand without the crank itself turning.

 

There's your answer. The damper is critical for elimination of damaging harmonics in the crankshaft caused by torsional deflection as the cylinders fire.