How To Tune an Opti-Spark Ignition System

Opti Spark Tune Up 1994 1996 Caprice Impala

The engine bay of a '94-'96 Caprice/Impala is easily the most spacious of any LT1-equipped car, yet it can still be intimidating, particularly if you're not one to wrench on late-model stuff. Buried in there is the Opti-Spark ignition distributor, itself a bit of a fearsome device, but servicing it is no big deal, as you'll see.

The engine bay of a '94-'96 Caprice/Impala is easily the most spacious of any LT1-equipped

Man, time flies. It seems like just a couple years ago when GM introduced the first major renovation of its small-block, but of course, that was back in 1991 for the '92 Corvette. At the time, one of the big deals of the Gen II engine was the Opti-Spark ignition system, which was driven directly off the cam and treated the engine "like eight one-cylinder engines," according to GM, in reference to the system's agility in constantly adjusting ignition timing based on need. The Opti-Spark system still used a distributor and conventional spark-plug wires, but it seemed to be considered a maintenance-free device, at least if the 100,000 spark plugs were any indication. But now the youngest of LT1-powered cars have been on the road for about nine years, and it's pretty common to see them with well over 100K on the clock. What's more, time has shown that LT1s tend to be hard on their ignition systems, if only because the plug wires are routed behind the exhaust manifolds where they are frequently baked prematurely. The resulting increases in resistance can in turn stress the distributor cap, and that's where a lot of guys get hung up.

If it isn't the fear of the unknown causing hesitation in tearing the system open, it's the lack of available parts, or at least their unusually high cost. Apparently, since GM didn't intend for this system to need frequent maintenance, the cap and rotor were not initially available on their own, and a whole new Opti-Spark unit had to be purchased. Later, the cap and rotor were sold separately, but often at a price that made the complete Opti unit seem more attractive. Now MSD has stepped up to offer its own version of the Opti-Spark cap and rotor, and by the time you read this, a complete, billet-housing Opti-Spark distributor. Both the cap-and-roller sets and complete distributors will be offered in early and late designs to cover all LT1 applications. We'll tackle the simple tune-up parts and illustrate that getting the job done on a Caprice/ Impala, isn't so bad. Have a look.

Within a few minutes, and with a few twists of a flathead screwdriver, the air inlet ducting and radiator hoses are removed (obviously, make sure the car is cool first), making the front of the engine a little less cluttered. The bad news is the water pump, air pump, and crank balancer all have to come off to get to the Opti unit, but it really isn't that tough once you know where the fasteners are and the removal procedure.
Within a few minutes, and with a few twists of a flathead screwdriver, the air inlet ducti
If GM hadn't used one of the water-pump bolts as a mounting stud for one of the air-pump bracket's mounting ears, the air pump could stay in place while the water pump comes out, but it did, so it does. There are three bolts holding the electric air pump to its bracket--a 10mm socket easily removes them, and then the pump can be swung out of the way with its hoses and wiring intact.
If GM hadn't used one of the water-pump bolts as a mounting stud for one of the air-pump b
The air-pump bracket has three mounting bolts, and a 916 will get them if you don't have a 14mm socket. The bolt over the water-pump stud accounts for one, another is in the center of the bracket, and a third is tucked behind a spark-plug wire. Pull the second wire from the top on the left bank and stick the socket through to the bolt.
The air-pump bracket has three mounting bolts, and a 916 will get them if you don't have a

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.
Now the six water-pump bolts can come off, releasing the pump. Expect coolant to come out
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.
When the bolts are out, break the gasket's seal and carefully pull the pump straight off (
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.
The crank balancer on the LT1 looks like a typical small-block Chevy piece. Fortunately, i

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.
Finally, the Opti-Spark unit is revealed. Only three bolts fasten it to the engine, but be
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.
On the bench, the four tiny bolts holding the distributor cap to the Opti housing are more
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).
The new MSD Opti-Spark cap and rotor are direct replacements, though MSD claims they're mo

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.
After plugging the vent hoses back in place, the Opti unit is returned to the engine. Don'