Join Date: Aug 1998
Location: Waldorf Md. USA
The 84 damper should be ok. All the 454 dampers are basically the same. The flywheel should also be ok as long as you purchased it for an 84 motor. The 454 flywheels changed around 1991 when they went to the one piece rear main seal.
Did your crankshaft have a pin in it to correctly locate the flywheel ? It is pretty rare to see a 454 without the pin, but I have seen them. If the pin is not there, the flywheel could be in the wrong position.
The next thing I would be doing is removing all the belts (water pump, alternator etc) and run the motor for a few minutes. As long as you dont get real carried away with revving it up, you can run it at least 5 minutes like this without causing any damage. If the vibration goes away, start looking at the fan, water pump, alternator etc as the cause.
The next test would be to remove the flywheel dust shield, unbolt the torque converter and pull it back away from the flywheel. You can run the motor like this without causing any damage. If the vibration goes away, the problem is in the converter or trans.
By the way, solid motor mounts, or bad rubber mounts can also make a bad vibration. Also make sure nothing from the motor, such as an exhaust pipe, is hitting anything under the car.
Hope this helps,
Advanced Automotive Machine