GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Catalyst (Gasoline)


On some older vehicles, the catalyst can be replaced while the converter is on the vehicle.


Through 1981
  1. Raise and support the front of the vehicle safely using jackstands.

The catalytic converter can be the hottest part of the exhaust system. Make sure the system is thoroughly cooled before attempting to remove the catalyst.

  1. Connect an Aspirator tool No. J-25077 to the tailpipe.

If the vehicle has dual exhaust systems, attach the aspirator to one pipe and plug the other.

  1. Connect a 60 psi air hose to the aspirator, to hold the beads in place when the plug is removed.
  3. To remove the converter fill plug, perform the following:
    1. Threaded Plug - Using a 3 / 4 in. Allen wrench or tool No. J-25077-3, remove the plug from the bottom of the converter.
    3. Pressed Plug - Place a cold chisel between the plug and the converter shell. Deform the plug until it can be removed with a pair of pliers.


When using the chisel, be careful not to damage the converter shell. DO NOT pry on the plug, for it may damage the converter's sealing opening.

  1. Connect the Vibrator tool J-25077-6 to the converter so that the canister aligns with the converter opening.
  3. Disconnect the air hose from the aspirator and allow the beads to drop into the collecting canister.
  5. Connect a 60 psi air hose to the vibrator and allow the excess beads to be removed from the converter, then disconnect the air hose. Remove the canister from the vibrator and discard the used catalyst.
  7. Fill the container with an approved replacement catalyst.
  9. Install the fill tube extension to the vibrator fixture.
  11. Connect the air hoses to the aspirator and the vibrator, then attach the canister.
  13. After the catalyst stops flowing, disconnect the air hose from the vibrator. Remove the vibrator from the converter and check to see if the catalyst if lush with the fill plug hole (add catalyst if necessary).
  15. To install the converter plug, perform the following:
    1. Threaded Plug - Apply an anti-seize compound to the threaded fill plug; install it and torque to 60 ft. lbs. (81 Nm)
    3. Press Plug - Use a service plug. Install the bolt into the bridge, then the bridge into the converter's hole, by moving the bridge back-and-forth to dislodge the catalyst beads until the bridge is positioned. Remove the bolt from the bridge then position the washer and the fill plug (dished side out) over the bolt. Install the assembly to the bridge 4-5 turns and release the full plug (the aspirator will pull the plug into position). Torque the bolt to 28 ft. lbs. (38 Nm).

  17. Disconnect the air hose from the aspirator.
  19. Start the vehicle and check for leaks.