Are your classic Corvette’s headlights so dim that fireflies try to mate with them? If you have driven late-model luxury cars at night, particularly European or Japanese models, you may have headlight envy. We’ll take a look at new headlight products and technologies that were not available or even legal when the first half million Corvettes were produced.
Headlights have undergone radical transformations over the course of automobile development. The first automotive headlights were actually lanterns that burned acetylene or oil. Use of lanterns continued for decades partly because the roads were so rough that the filaments in electric lights couldn’t take the abuse. In addition, early automotive electrical systems were weak. That began to change in 1912 when Cadillac introduced a major automotive first: a complete automotive electrical system with electric starter, generator, starting battery and lights.
From then until 1939, automotive headlight design was as wild as the West. There were all shapes, sizes and numbers of headlights due to lack of federal regulations. That ended in 1940 when all American-made cars were required to have two 7-inch diameter round headlights with high and low beam filaments. Sealed into one unit were the filaments, diffusing glass lens and parabolic aluminized reflector (labeled PAR56). This “sealed beam” was impervious to water and dirt. At last, a car owner could easily find a replacement headlight for their vehicle in any town.
Federal regulations were expanded slightly in 1957 to allow automakers the option of using four smaller 5 3/4-inch sealed beam (PAR46) headlights. By 1958, most of the pricey American cars switched to four headlights, including the Corvette. Two different bulbs were used in these quad headlight systems. One had high and low beam filaments like the previous 7-inch sealed beam. The other had only a single filament for a high-beam.
The next change in U.S. regulations occurred in 1975 and allowed the use of rectangular headlights in two sizes. These were first seen on Corvettes when the C4 debuted in 1984. This same year all U.S. auto manufacturers were allowed to use composite headlight assemblies, which have small, replaceable bulbs.
All this time European regulators were choosing a different path. For years they had allowed glass or plastic covers over the headlight for a more streamlined body contour. Some US-market cars achieved this sexier silhouette with hideaway headlights. Finally, the U.S. regulators relented to allow the clear aerodynamic headlight covers, which appeared on C6 Corvettes in 2005.
The Europeans also chose a different path in the design of the bulb and reflector. They allowed a much brighter bulb but required that the light pattern have a sharp cut off at the top to restrict the light reaching the eyes of on-coming drivers. By contrast, U.S. regulations called for dimmer headlights with a wider light distribution pattern. It is said that the U.S. regulations made it easier to see overhead signs at night but created more glare from oncoming traffic.
The differences in bulb brightness and the headlight pattern are important to know when choosing to upgrade headlights. Brighter bulbs may not be legal in the U.S. for on-road use and they may draw more current (amps) than the original wiring system was designed for. Also, if the bulb and the reflector were not designed to have a sharp cut off at the top of the light pattern they may create considerable glare for on-coming drivers.
Most automotive headlights continue to use a metal filament, typically tungsten that is heated by the electric current passing through it until it glows nearly white-hot, just like your common household incandescent bulb. At this high temperature, some tungsten eventually evaporates from the filament and is deposited on the reflector or lens. You may have seen older headlights that are blackened by this. In the mid ’70s, halogen headlights arrived in the U.S. and they now dominate the market. Halogen sounds high tech and marketing people love to use the term. However, only a small amount of halogen, a chemical group that includes the common chemicals fluorine, chlorine, bromine and iodine, is used inside the bulb.
The halogen helps prevent the evaporated tungsten from adhering to the glass and actually enables some of the tungsten to be re-deposited on the filament. The advantages are bulbs that can run hotter and thereby produce more light per watt, that maintain their intensity and that have a longer rated life. Because halogen bulbs run hotter, replaceable bulbs use quartz glass. It’s important to note that they run so hot that the glass can fail if there’s even a small amount of dirt or a fingerprint on it. Also note that the common halogen-tungsten bulbs are sometimes called quartz-halogen or quartz-iodine to sound more high tech.
The name confusion continues with xenon-tungsten and halogen-infrared bulbs. Some tungsten filament bulbs have xenon added to produce a light output with a blue hue, similar to the high-end high intensity discharge (HID) headlights, which use xenon. And they are described as xenon bulbs, a description previously only used for HID bulbs.
Another confusingly named tungsten filament bulb is the halogen-infrared. By applying a special infrared reflective coating inside the bulb, the filament’s infrared emissions are directed back into the bulb heating it further. The result is more light output and less heat output per watt. These halogen infrared bulbs are named HIR, confusingly similar to HID. However, both xenon-tungsten and halogen-infrared bulbs can replace standard halogen tungsten bulbs; they don’t require the HID’s expensive electronics.
HID stands for high intensity discharge and is basically a metal halide arc lamp. The light is produced when electricity passes through a gas, causing it to glow. Think street lamps. They are often called xenon lights because it sounds cool and because they contain xenon gas. One of the first U.S. cars to use HID headlights was the 1996 Lincoln Mark VIII and today their use is generally found in luxury brands. The C6 Corvette came with an HID low beam and a tungsten halogen high beam.
The xenon gas helps HID lamps reach full illumination faster than street lamps do, a necessity in automotive use. However, a ballast and igniter are required—like for a neon light—to produce a higher voltage to get the electricity flowing through the gas. The extra parts add to the initial cost, the replacement cost and the repair cost of HID systems. Although HID bulbs (technically called capsules) may require less current during use, upgrading to an HID system may require rewiring and a relay to handle the increased current draw during startup.
HID lamps produce significantly more light per watt than standard bulbs that have filaments. The light is often whiter and can have a blue tint. Some say the narrow HID color spectrum provides more detail and is easier on the eyes of the driver. Others say it causes more glare for oncoming traffic. There is agreement that HID bulbs can last much longer than halogen bulbs and handle shock and vibration better because they have no filament. The bulb’s rated life is not the entire cost picture though because the ballast and ignitor that HID’s require can fail, too.
Bi-xenon headlamps use a single HID bulb for both the low beam and high beam. This enables a single headlight on each side of the car. The low beam is partially shuttered by a moving plate, or in some systems by moving the bulb down. C7 Corvettes came with bi-xenon projector headlamps.
LED bulbs are the most recent headlight development and are a radical departure in terms of technology. Standard filament bulbs and HID bulbs heat a metal filament or a gas respectively until it’s so hot that it glows. LEDs use semiconductors to produce light. Photovoltaic cells turn light into electricity; LED lights do the reverse. In most applications, LEDs produce far less heat and more light per watt while lasting longer. LED bulbs continue to replace small filament bulbs throughout the car (and our homes).
Making an LED bulb as bright as is needed for a headlight has been a challenge. The LED headlight bulb itself does not get as hot as a filament or HID bulb. However, a heat sink or fan, like is used on your computer’s microprocessor, is generally required to keep a LED headlight bulb cool enough to prevent damaging the semiconductor. Only in the last 10 years have auto manufacturers begun to use LED headlights technology, with the 2009 Cadillac being one of the first U.S. applications.
When considering LEDs as a headlight upgrade, be mindful of the cost, current reliability, light output and illumination pattern. Beware also that some headlight housings marketed as LED still use halogen bulbs for the headlight but add smaller LEDs for use as daytime running lights or just for extra bling.
Halogen, HID and LED denote different types of bulbs. Projector headlights denote a different construction of the lens and reflector assemblies, which can be designed for the different types of bulbs. Standard headlights use a parabolic shaped reflector, think bowl shaped. Projector headlights use an elliptical shape reflector, think champagne flute, making them much smaller in diameter but much longer. They also employ a thick, clear, convex lens in front to focus and direct the light.
Projector headlights are easy to spot when walking through a parking lot. They’re typically two and half inches in diameter or less and have a thick lens. Their appearance and small form factor are prime reasons for their popularity. With the absence of chrome bumpers and reduced use of chrome ornamentation, modern lights have become the jewelry on cars. Multifaceted silver reflectors, glitzy lenses and projectors add more visual appeal than the relatively boring old sealed beam headlights.
Color Temperature and Light Output
Bulbs are sometimes rated in color temperature, expressed in kelvins (absolute temperature). Advertised color temperature is often a style consideration. People who want the blue or even purple hue to their headlights will choose bulbs with higher color temperatures. Incandescent (filament) bulbs produce a wider range of color than most HID or LED bulbs. Original equipment tungsten bulbs produced light with a slightly amber hue under the 3000K range. Halogen tungsten bulbs produce a higher color temperature with less of the amber hue. The light from HID OEM bulbs looks much more white by comparison at around 4300K.
Aftermarket HID bulbs are offered in higher color temperatures, but note that HID light output per watt goes down as the color temp goes up. 5000K is a very bright white while 6000K has more of a bluish hue. 8000K and 10000K color temperatures produce a violet hue. The highest color temperature bulbs are generally chosen simply for their bling. There’s no consensus about what color temperature is better for visual acuity at night. Note that filament bulbs produce visible light over a wide spectrum and thus have fairly good color rendition. Many HID lights produced light in a narrower range, as do some LED bulbs. Don’t be too judgmental about the color of somebody’s car or clothing under these headlights.
Light output is generally proportional to wattage for filament bulbs like halogens or common household bulbs. A 55-watt halogen bulb produces significantly more light than a 35-watt halogen. HID and LED bulbs are also rated in watts because that’s important for determining wire size. However, these bulbs produce much more light per watt wattage so lumens or CP when listed is the most useful light output comparison available. Take these light output ratings with a grain of salt because the amount of light transmitted to the road where you want it is what’s most important. That can vary greatly depending on the reflector and lens.
Choosing Upgraded Headlights
Be aware that there’s a lot of hype in the advertising of performance headlights and bulbs. The best way to judge a bulb’s performance is to compare side by side with the car that has the bulb installed. Lacking that, customer reviews can be useful if there are a lot of them. It’s human nature for a person to brag or exaggerate about the value of upgrades they’ve made. I place more weight on detailed negative reviews. (As an example, one HID kit had 10 reviewers saying their headlights were much brighter now. However the next reviewer stated the new headlights blinded other drivers and had to be removed.)
For C4-C7 Corvettes, upgrading headlights can be as simple as replacing the lamp or bulb. However, be aware that the reflector and housing were designed to produce a very specific light distribution pattern with its bulb’s light source in a specific location. When changing from a filament bulb to an HID bulb or an LED bulb, it is critical that the new light source is located in exactly the same spot on the bulb or the light distribution will be way off. This can mean even though the bulb is brighter, there can be less light on the road.
This is equally important when choosing bulbs for conversion headlight assemblies that are made to replace sealed beams. If a 5 3/4-inch Hella headlight housing was designed for a standard H4 or H1 halogen bulb, then that’s the safest bulb to use. Placing a HID or LED bulb into a housing designed for a halogen bulb can result in a light output that is much brighter but it may scatter this light all over the place, and dangerously into the eyes of oncoming drivers.
For C1-C3 Corvettes, upgrading headlights is more complicated. Consider these options, starting with the wiring. If a small improvement in light output is all that’s needed, check the voltage at the headlights and install a relay if the voltage drop is much over 1 volt. Improvement may also be gained by switching to tungsten halogen sealed beams from the original tungsten sealed beams. If even more of an increase in light output is desired, it’s time to look at a headlight conversion.
A nearly stock look can be obtained by replacing the sealed beams with a conversion lamp assembly that uses replaceable tungsten halogen bulbs like the H4 bulb. Their standard wattage is 55/60, which is a significant step up from original sealed beams. Much higher wattage bulbs like the 90/130 watt H4s are also available although they are only approved for off-road use. It’s important to note that brighter is not necessarily better. When intense light is reflecting off the road closely in front of the car and bright light is scattering around, your pupil may not dilate as much, and you may be less able to see objects in the distance.
Many different conversion lamp assemblies are available for both 7-inch and 5 3/4-inch sealed beams. Some assemblies add LEDs or halo lighting for style. Other designs have a clear lens and a multisurface reflector, skull designs, or blue dots. As you’ll see, the light pattern they produce can vary widely. A conversion assembly marked SAE or DOT indicates that the light pattern is compliant with those standards. But be aware that the manufacturer self-certifies this. I’ve found that the actual light patterns still vary considerably. All things being equal, I prefer an ECE (European) headlight assembly because they had to be tested and approved by an accredited laboratory.
The following photos show options for upgrading headlights on most Corvettes, but most of the options featured here are for 1958-’82 models because there are so many choices for upgrades from the old quad headlight sealed beams. If you’ve been singing “It’s getting dark, too dark to see” while driving your Corvette at night then follow along for a remedy.
1. Surprisingly, there are many options for upgrading the old 7-inch sealed beam headlights. This Grote Industries LED headlight is DOT compliant and is but one of many offerings from Summit Racing. Perhaps there are so many choices for 7-inch headlights because of the popularity of customized and restomod older trucks.
2. The easiest headlight upgrade for C1 and early C2 Corvettes is accomplished by installing halogen sealed beam bulbs. “Halogen” should be evident on the lens if you already have them. Also, if you look closely behind the lens, there will be a separate enclosed bulb. The original non-halogen sealed beams will just have one or two bare filaments inside.
3. For a greater increase in light output over the original 5 3/4-inch sealed beam headlights, a conversion lamp assembly is needed. Many assemblies such as this IPCW Crystal Clear Diamond Cut Headlight from Summit are designed to use common H4 bulbs. This lamp has a nearly flat prismatic glass lens and costs only $14. It has no DOT or SAE markings but fits easily into the GM headlight retaining cup after minor bending of its three alignment clips.
4. The $30 United Pacific Conversion Headlight S2005LED from Summit is marked SAE and has a string of five yellow LED’s at the bottom. The LEDs have both a high and a low intensity and draw less than 0.02 amps. This conversion assembly has mostly vertical prisms on a rounded glass lens and comes with bulb, connector and wiring. Minor filing of the retaining cup is needed for full insertion of the alignment clips.
5. To protect the paint, apply tape along the edge of the upper panel. Then remove the painted headlight bezel for access to the bulbs. Two short screws with machine threads go into the cast housing at the top. Often these have been replaced with sheetmetal screws. On each side at the rear, a sheetmetal screw goes into a clip. Corvette America offers the original screws in a set.
6. If the headlight housing is adjusted too far down to allow easy removal of the bezel, loosen the lock nut on the headlight stop. Then turn the adjusting screw into the stop bracket until the headlight assembly can be raised enough to remove the bezel without endangering the paint.
7. To remove the headlight as an assembly, disconnect the spring from the retaining cup by pulling on the spring end with locking pliers or with a stiff wire with a hook. Alternately, just remove the three screws attaching the retaining ring. The spring, the adjusting screw with its bracket, the stainless steel retaining ring and the four different headlight retaining cups are all available from Corvette America.
8. With the engine running and the headlights turned on, measure the voltage at the headlight bulbs. Compare that to the voltage at the alternator. If the difference is 1.5 volts or more, just installing a simple relay can make a noticeable increase in light output.
9. The 40-amp fan relay from Summit (PN 19002) costs only $14 and is more than sufficient for any street-legal headlights. For ease of wiring it can be located in the left headlight assembly.
10. After installing the conversion headlight assembly, check to see how far it extends through the retaining cup. The Rampage cast housing extends 1/2-inch beyond the retaining cup. That’s just enough clearance to allow headlight adjustment without any modifications. If a conversion assembly extends more than that, the hole in the lamp housings of 1968-’82 Corvettes needs to be enlarged.
11. The $29 Rampage Replacement Conversion Headlight Assembly from Summit is marked DOT and SAE and has a nearly flat clear glass lens that extends out 1/2-inch. Its alignment clips fit tightly in the stock headlight cup without modification. Instead of prisms on the lens of a sealed beam, it has a multisurface reflector like the showy headlight assemblies on many new cars.
12. If you have the fiber optic lamp monitoring system, make sure any replacement lamps transmit light to the rear of the bulb at the center. This is easy to test before installation. Connect 12-volt leads to the bulb and look at the rear. Bright light should be coming through, as seen on the back of this halogen sealed beam headlight.
13. One advantage of choosing a headlight conversion that uses an H4 bulb: it plugs directly into the original wiring harness connectors. Another plus is that this Hella H4 60/55 watt bulb (60 watts for its high beam) costs less than $2 at Summit. Higher wattage H4 bulbs are available, too, although they may not be street legal.
14. The H4 bulb has a shield over its high beam filament. The exact placement of the filaments is necessary for the reflector to project the light properly onto the road. If an HID or LED bulb is substituted, the light will be reflected in a different pattern and possibly into oncoming drivers’ eyes.
15. This low beam light pattern shows a very even distribution of light. The sharp upper cutoff is good to keep the light out of the eyes of oncoming drivers. The kick up on the right is desirable for illuminating objects on the curb side of the road (for left-hand drive cars).
16. This high beam conversion assembly produced a well-focused intense light pattern, which is desirable for seeing objects far down the road.
17. By comparison, this high beam conversion assembly produced a fairly diffused pattern with light scattered around. You don’t want high beams illuminating the road directly in front of your car, or illuminating the trees.
18. Hella’s low/high beam conversion assembly is ECE approved. That means it has been inspected by an accredited laboratory that assures it meets the tough European standards. This assembly is available as a set of two headlights for $88 from Summit and includes Hella H4 bulbs.
19. For many applications, it’s essential to know how far back a headlight conversion assembly extends from where it mounts to the retaining cup. For C3 Corvettes, if it extends more than 2 1/8-inch, then some trimming of the inside of the headlight door can be required.
20. C4 headlight upgrades are easy and need no modifications with Hella’s 7x6-inch Rectangle Light Conversion from Tire Rack. It comes with Low/High Beam replaceable HB2 bulb and uses the vehicle’s factory wiring harness. DOT, SAE and street legal in Canada and the United States.
21. C5s can upgrade by simply installing different bulbs. Tire Rack has a selection of bulbs including PIAA Xtreme White Plus replacement bulbs. These are halogen bulbs available in both high and low beam that PIAA says produces “a brilliant cool white light that comes very close to the color of expensive High Intensity Discharge (HID) lighting systems.”
22. To determine the actual wattage of a lamp, use a jumper and an ammeter to connect it to 12 volts. Also measure the voltage at the lamp when it’s connected. Multiply the two readings to calculate the wattage. This halogen high beam measures about 34 watts. This value at 12.2 volts should be adjusted up a little because bulbs are often rated at 12.8 volts.
Photography By John Pfanstiehl