Vacuum Sucks!

Finally! A C3 Electric Headlights Conversion Kit

Rob Wallace III Jun 14, 2004 0 Comment(s)

We probably don't need to explain the woes of vacuum-actuated headlamp rotation to any of the '68-82 Corvette owners out there. If you own or have been around Sharks for any time at all, you're undoubtedly familiar with the shortcomings inherent with the vacuum system that rotates the C3 headlights (and windshield wiper door as well on the '68-72 models). The vacuum system tends to be every bit as vulnerable as it is complicated, and it's prone to lose performance if not outright failure.

Over time, the rubber hoses and other components of the vacuum system age and wear out. Also, the headlamp rotation gets slower and slower and inconsistent, and the "frog-eyes" begin "winking" at you (one side rotating faster than the other), until at some point they simply wink out. Most of the vacuum system components are being reproduced and are available on the aftermarket, and we walked through the process of restoring the vacuum system on a '72 Corvette last year ("Into the Void: Parts I, II, and III," Dec. '02, Feb. '03, and Mar. '03). But what if irreplaceable components, like the master vacuum reservoir on the early Sharks, won't hold pressure or you have a big motor or a hot cam with a lot of duration that doesn't create much vacuum in the first place?

Well, it's no longer necessary for those vacuumless Sharks to live out their days--as well as nights--with the pop-ups fixed in the open position. Chris McDonald of McSpeed Performance designed a way to replace the stock vacuum setup with late-model GM electric headlight actuators using his '69 killer Shark roadster (see "The Need for McSPEED," Mar. '03) as the guinea pig, and he has created a kit to make the conversion as simple as possible. The McSpeed Killer Lights kit includes all the brackets and hardware necessary for mounting a Fourth-Gen Pontiac Firebird electric actuator system on any C3 Shark. Then, depending on how much time and/or money you're willing to spend, you can search for the necessary used electric components (even many worn-out electric actuators can be rebuilt, as we will illustrate), simply pay a visit to your local GM dealership's parts department, or a combination of both.

Michael Meyers, President of Dreamworks Performance Engineering in Sheridan, Colorado, was happy to provide his highly modified '75 Shark ("Feeding Frenzy," Aug. '03) for our installation. Since he's modernized so many other aspects of the '75, Mike's Shark seemed like a natural to us for this update. Instead of scrounging around for used parts, which is a completely viable alternative for those individuals willing to devote the time, we opted to order all the necessary components that Chris recommends from Purifoy Chevrolet in Fort Lupton, Colorado. Although we are starting with brand new actuators, the nylon gear that GM installs in the Firebird actuators is notorious for wearing out. (Yup, it's the same fragile kind used in C4s and C5s, as well.) We decided to preemptively fix the weak links by replacing the standard nylon gears with virtually indestructible CNC-machined brass cogs from Brent Franker before installing the new actuators.

With the conversion complete, the '75's headlamps now speed immediately up and down with no sluggishness, no delays, and no issues about going one at a time--and the motor doesn't even need to be running! Finally, a solution to vacuum that doesn't suck!


The 58-piece McSpeed Killer Lights Kit consists of the brackets, bumpstops, spacers, and hardware necessary for adapting late-model GM electric actuator components into all C3 Sharks in an OEM fashion.

Shown clockwise from left to right is the: left-hand '93-97 Firebird headlight actuator, lift arm, and Firebird mounting bolts (all sold together new, GM PN16516653); '90-96 Corvette Headlight Control Module; '84-89 Corvette Headlight Switch (GM PN 1995257); right-hand Firebird Actuator, lift arm, and F-body mounting bolts (sold as a unit, GM PN 16516654); '93-97 four-wire Metri-Pack pigtail (GM PN 12102776); and '93-97 five-wire Metri-Pack pigtail (GM PN 12102775). Also needed but not shown here are two Actuator Connector Packs (GM PN 15306302), sold individually.

Our first step was to replace the nylon gears in the electric actuator motors with the CNC-machined brass cogs. On '93-97 Firebirds, like '97-99 C5s, the headlight actuator is glued together. The seal should be carefully cut open with a razor, and then the gear cover can be easily pried off with a small screwdriver. Here, we have the metal shaft, brand new nylon gear, and its unused rubber bumper sitting beside the brass gear (top right) that was ready to go in.

The metal shaft was fitted directly into the slots on the brass gear, thus there is no need for either the nylon gear or the OE rubber bushing. Reseal the gear cover with epoxy (being careful not to get it on the gear), then let it cure for 24 hours. Mike wrapped the resealed actuators with strips of duct tape and a pair of C-clamps each to ensure a tight bond.

It was time to remove the old vacuum system, beginning with the vacuum actuators. From underneath the car, Mike slipped the linkage pin out of the left actuator rod clevis. There are two linkage springs that must first be disconnected from the linkage pin, and the cotter pin that holds the linkage pin in place must be pulled out. There is also a plastic washer on the linkage pin and two plastic oval inserts that should come free as the linkage pin is removed. All of these parts are needed in the reassembly, so be gentle in removing the parts and keep track of them, as you should be able to reuse them.

Once the linkage pin is removed, unscrew the clevis from the end of the actuator rod. Then, while still under the Vette, remove the four bolts that attach the actuator to the headlight bracket, and the actuator can be pulled free from above. It is much easier to access the headlamp areas with the hood removed from the car.

Next, it was time to begin removing the snake pit of rubber vacuum hoses from the left- and right-side vacuum relays mounted between the right-side headlight bracket and the horn.

From underneath again, Mike removed the bolts that hold the vacuum relays in place (two bolts apiece) and pulled the relays from the car.

Out with the old, in with the new. After the vacuum actuation system was completely removed from the C3, including the vacuum lines that run to the vacuum canister and the various relays that go to the motor and the controls on the dash, Mike prepared the Firebird actuator arms for their C3 application. First, center-punch the pivot pin and drill through it with a 3/8-inch bit. They are double-reinforced and require some patience.

The pivot pin was now replaced by a 3/8-inch hole and was quickly deburred with a file.

Mike test-fits the linkage pin in the actuator arm's new hole and found that everything fit together perfectly.

Next, Mike prepared the other end of the actuator arm for the new bumpstop, drilling a 3/16-inch hole in the tip.

Mike aligned the bumpstop to the actuator arm in the closed position and marked the proper positioning of the bumpstop to the new hole in the actuator arm with a Sharpie. He then proceeded to drill a matching 3/16-inch hole in the bumpstop.

Then, using the 3/16-inch rivet supplied in the Killer Lights Kit, rivet the bumpstop to the actuator arm. Mike shows the finished left-side actuator arm in the closed position, ready to be installed.

With a straight-edge and a Sharpie, draw horizontal lines across the exact center of vacuum actuator mounting holes to the inner edge of the headlight bracket. Then use the straight-edge to draw vertical lines from both edges of the actuator rod hole to the bottom of the bracket. The electric actuator arms require more room for travel than do the vacuum actuator rods, so we cut open the bottom of the hole.

With a cutting wheel, Mike sliced through the headlight bracket to remove the material in the way of the arm. It may not be necessary in all applications to remove this area entirely, but the original hole will need to be extended at least for the actuator arm to function properly.

Next, Mike used the McSpeed actuator bracket as a template to drill two 1/4-inch holes in the inside edge of the headlight bracket. Line up the centers of the bottom bolt holes in the actuator bracket along the horizontal lines drawn on the headlight bracket to find the proper location for the holes in the side.

After the holes are drilled in the side, loosely fasten the actuator bracket to the headlight bracket, using the 1/4x20x3/4-inch bolts, washers and lock nuts supplied in the McSpeed kit. Three bolts are provided for each side--two to attach the new bracket, (the lower bolt also being used to reattach the support rod from underneath as it was on the vacuum actuator) and a third to attach the second support rod on the other side of the cutout (see arrow).

Attach the electric actuator to the bracket (being sure to have it properly oriented and using the left one on the left side, etc.). Mike first inserted the two 1/4x20x3-inch bolts through the actuator on the arm side (through the actuator bracket), slipped a McSpeed spacer tube onto each bolt between the actuator bracket and the stock headlight bracket, and finger-tightened a washer and lock nut to the bolts after they passed through the headlight bracket flange.

After installing a 1/4x20x2-inch bolt and washers through the third (upper) hole in the actuator and actuator bracket and tightening by hand only, slip the actuator arm onto the motor's shaft and tighten the nut loosely. Then reattach the linkage pin through the clevis mount and the Firebird actuator arm as you would have with the stock clevis. Be sure to put the plastic washer and oval inserts back in with the linkage pin and secure it with the cotter pin. Now that everything is loosely attached, it's the right time to be sure everything is aligned perfectly and adjusted as necessary.

When the actuator motor and arm are properly aligned, begin tightening all of the attaching nuts, starting with the 3/4-inch bolts on the underside of the headlight bracket assembly. Then, turning the knob at the end of the actuator, manually adjust the headlamps up and down to seat the headlamp doors properly to the body when closed. Also adjust the aim of the headlamps in the open position as necessary by loosening the three mounting bolts for the pivot armature from below using a 1/2-inch socket.

With the actuators mounted, it's time to install the electric control module. We decided to mount the module in the same location that the vacuum relays were originally located. Mike fabricated a mounting bracket for the module out of a piece of scrap stainless steel and took a tracing from the car of the mounting holes where the relays were attached. Then, Mike transferred the location of the holes he found to the top of his module bracket and drilled the hole for the screws.

He found a couple of bolts that were the right size and thread pattern for the electric module and attached it to the bracket...

...and then mounted the module bracket to two of the vacuum relay mounting holes, reusing a pair of the original relay bolts. Voila! The electric module serves the same function as the vacuum relays, and is mounted in the factory location, which will lead to a very OEM-style appearance. Plus it is safe from the elements and is easily accessible.

Mike fit the four- and five-wire Metri-Pack pigtails to the module and labeled each wire by the letter associated with it on the module. He then disconnected the pigtails and wrapped the wires with loom tape (less sticky than regular electrical tape) to keep them neat and orderly, not to mention OE-appearing.

Then he plugged the wrapped and labeled wires back into the electric control module.

Next, Mike plugged the two-wire Actuator Connector Pack (GM PN 15306302) into the actuator plug, after labeling and looming those wires as well.

Using bulk wire, Mike created a very long four-wire, 14-gauge wiring harness to connect the actuators to the C3's electrical system. The wiring harness is about 14-feet long, much longer than necessary, but it's better to trim off the excess wire than have to splice on extensions. Naturally, it is wrapped up and fully self-contained within loom tape.

Mike camouflaged his wiring harness by running it along the left-side inner fender with the factory wiring harness, and he loomed both the OE and homemade wiring harnesses together.

After wrapping the new wiring harness around the core support as inconspicuously as possible, Mike ran it along underneath the lip of the front end and tucked it neatly out of sight using original connectors.

With all the necessary wires now at hand, Mike connected the Firebird wires to his wiring harness with the GM double-crimp and heat-shrink connectors supplied with the GM connectors.

When all is said and done, the electric headlight actuators and module look like they were put there by the factory.

Now that we're done under the hood, it was time to replace the stock headlight switch with the C4 switch to control the electric system. In order to do this, you must at least partially disassemble the dash. After undoing the attaching screws from the console and instrument cluster area enough to gain access to the light switch assembly, Mike removed the light switch knob and inserted a large screwdriver in its opening to detach the stock light switch.

Once the switch is detached from the instrument panel, unplug the harness connected to it and it can be pulled free of the dash.

The early C4 light switch (right) is very similar to the stock '75 light switch we just removed (left).

Behind the firewall, Mike split his wiring harness into two pairs of wires. The controlling pair were spliced into the C3 wire plug that attaches as a unit to the light switch.

Once the C4 switch is in place and the new wires spliced into the plug, attach the plug to the new switch, reinstall the original C3 light-switch knob and shaft, and button the dash back up.

Mike ran the remaining half of the wiring harness--the power and ground wires--behind the kick panel, under the door sill plate, and up to his custom fuse box.

Drop-down electronics bays--like Mike has created behind the seats in his '75--never came standard in C3s, but the principle is the same. Mike connected his lead wire to fuse panel, attached the ground wire, and installed a 30-volt fuse. GM powers the left- and right-side actuators on separate circuits with a 15-volt fuse for each so that at least one headlamp is usable if the other circuit fails. Since the '75 is a toy rather than regular transportation, Mike saw this as redundant and chose to power both actuators together. With that, the installation is complete. The electric headlight actuators now zoom up and down like lightning!