Opti-Spark Ignition System Tune-Up

Now the six water-pump bolts can come off, releasing the pump. Expect coolant to come out of the bolt holes, even after you drain the radiator.

When the bolts are out, break the gasket's seal and carefully pull the pump straight off (it has two mounting dowels), taking care not to drop the splined drive collar. We'd recommend leaving the collar on the pump's shaft so you don't forget to put it back.

The crank balancer on the LT1 looks like a typical small-block Chevy piece. Fortunately, it mounts to a separate hub, so it doesn't require a puller for removal. Just remove the three bolts and rock or gently tap it off the crank hub.

Finally, the Opti-Spark unit is revealed. Only three bolts fasten it to the engine, but before removing them, pull the plug wires (mark them if it's not obvious where they go) and the electrical harness connector. The 10mm socket will remove the three bolts--the top two are easily seen at the top of the unit; the bottom bolt is on the right of the bottom. With the bolts out, carefully pull the unit off and disconnect the two vent hoses.

On the bench, the four tiny bolts holding the distributor cap to the Opti housing are more apparent. They use an unusual inverted Torx-style head, which most of us don't have a tool for. The techs at MSD claim the company'scap and rotor sets will include the required tool, but our test cap didn't. We used a trick we found on the Internet of using one of the throttle-body top plate screws as a socket. Wrap the screw in tape to protect the threads and then clamp it with a small vice grip. Now it can be used to remove the Opti's bolts. Note: The likelihood of the throttle-body screw's threads being damaged is high.

The new MSD Opti-Spark cap and rotor are direct replacements, though MSD claims they're more durable and resistant to internal breakdown. They're also competitively priced with factory stuff ($150.88 at summitracing.com). The MSD Opti cap and rotor sets will include a new seal, hardware, and the aforementioned tool, but like the tool, we didn't get the seal or hardware with our test kit. Luckily our factory stuff was fine and we bolted it all back together. Order PN 8481 for early LT1 ('92-'94) and PN 84811 for late ('95-'97).

After plugging the vent hoses back in place, the Opti unit is returned to the engine. Don't worry about synchronizing the timing--it will only interface with its drive in one position. Now is a good time to replace questionable oil seals and definitely the right excuse to do the plug wires, but be warned, it's not fun. Tech tip: Accessing the plug wires on an LT1 is often easier through the wheel wells with the wheels removed. You can get a set of pre-made LT1 wires and a new coil from MSD as well.