1974 Corvette MSD Ignition

Have you ever noticed that when you talk to someone about their hot rod performance vehicle (whatever it may be), they talk about compression ratio, cubic inches, carb size/cfm, and an MSD ignition? Over the many years that I have been building racing engines, I guess I will always assume that to upgrade the ignition system of a high-performance engine, MSD is the way to go.

What is it about this MSD ignition system that makes it so popular among us gearheads? It’s almost a status symbol. The answer you get may vary from other engine builders, but after installing literally hundreds of MSD system combinations from street rods to IHRA funny cars, I think the best answer should be heard from MSD’s biggest and most loyal fan--me. And the best way to do that is to install a complete system in this 1974 Corvette.

The system combination chosen for this installation was the 6A ignition box, a Blaster II coil, a Pro Billet distributor with a tach drive and vac advance, and an MSD ignition wire set. Our 1974 was a unique vehicle to choose for this system in two ways. One, this was the last year that Corvette used a mechanical tach drive and, two, this was the last year to use points.

Removing the original ignition system (the ignition/spark plug wires in particular) is not necessarily an easy task, especially if you decide to install the new ignition wires in their original locations. GM went to great lengths to ensure the longevity of the ignition wires in the Corvette's unique engine compartment and exhaust system configuration, requiring removal of exhaust manifold heat shields, steel plug wire looms, and even the starter.

So, disconnect the battery first. The distributor is removed by loosening the 9/16-inch-headed bolt at the base of the housing, then sliding the clamp back. Take note of the rotor and distributor housing position. Sometimes, turning the motor over to point the rotor straight ahead makes it easier to reinstall the new distributor in the right place the first time. Then disconnect the tach-drive cable by unscrewing the cable collar.

Last, remove the coil-and-condenser assembly from the coil clamp. Leave the clamp bolted to the intake manifold, as the MSD Blaster II coil can be mounted securely in the original clamp. The wires connected to the old coil can make this conversion a little confusing, but it’s actually quite simple. The wire to the coil negative terminal from the original distributor will not be used, and the wires from the condenser assembly will not be used, which leaves the wires from the engine harness to the coil’s positive terminal. In our 1974, the two wires (spliced to one connector) originally connected to the coil’s positive terminal, will be used as the "switched power" source to turn the ignition box on and off.

Install the new distributor into the engine, taking care to phase the new rotor in the same position as the old one. If the distributor doesn’t drop all the way in, pull it back out and, with a long-shafted screwdriver, turn the oil pump driveshaft slightly so it aligns with the distributor shaft during installation. Just snug the distributor housing clamp for now. Install the coil and tighten the holding clamp. Mounting the MSD 6A box in our 1974 was pretty straightforward, as there was only one place to put it (where you could see it under the hood). The box can be mounted in any position, except upside down, to ensure drainage of moisture.

Wiring our new ignition system was easy. The two heavy-gauge wires, red and black, were connected to battery power (constant/unswitched) and ground, respectively. The smaller red wire connects to the wires that originally connected to the coil positive terminal. A simple butt connector does the job, though sealing a soldered connection with heat shrink is suggested. The orange and black wires, in their own separate conduit right out of the box, are the only wires connected to the Blaster II coil, orange to positive, and black to negative. Since we chose to use an MSD distributor, connecting the "trigger" wiring was as simple as plugging in the magnetic pickup harness and eliminating the white (points trigger) wire from the circuit. That's it!

The MSD ignition wires come with only the distributor end, allowing custom lengths and different spark plug boot angles to be created by the installer. They even include the special tool to make that factory-looking crimp with every wire set. The owner of our 1974 decided he wanted all to see his latest upgrade, so we opted not to run the ignition wires back on the original looms.

The installation was complete, though some tuning is required. The ignition timing must be set--check the spark curve adjustments and spark plug gap. These actions are all part of getting the most out of this particular investment.

MSD’s commitment to versatility, reliability, and ease of installation is obvious. However, the best part of this MSD conversion is a noticeable bang-for-the-buck performance improvement over stock. Our 1974 Corvette started better, idled more smoothly, had improved throttle response, and more overall power. And it was all noticeable. Now, if I could only talk him into the supercharger. Nitrous fogger system...