story and photos by jim clark, the hot rod md
choosing and mounting headlights on a hot rod is a three-step process. first step is deciding how and where you intend to mount them. then you will need to select a style of housing. lastly you will need to decide which type of headlamp that you will use.
You're reading: Headlights Part 3: Choosing and Mounting Them
mounting fmvss 108 states that single multi-function lamps and individual lamps for each function must be mounted parallel at the front of the vehicle, as far out to the edge as possible. this was not always the case. headlamps were not available on all vehicles in the first decade of the 20th century and no standard for their mounting location or output existed. most headlamps at the time were separate units mounted close to the radiator shell or on a crossbar between the fenders.
in 1913 pierce arrow, one of the most expensive cars at the time, decided to mount the headlights into the front fenders and patented the idea. this prevented other automakers from mounting them there unless they paid a royalty. this explains why most other manufacturers mounted separate headlights on their vehicles until the patent ran out in 1934. ironically, pierce arrow, that was manufactured in buffalo, ny, had to equip their vehicles sold to residents of new york with separate headlight units like those sold on other vehicles because the state legislature, in their infinite wisdom, decided that the wide light pattern would confuse other drivers. so they passed a law making them illegal in new york.
this 1915 pierce arrow has the optional headlights mounted into the front fenders. new york state passed a law making them illegal there so residents of that state couldn’t order this option.
this late 1930s willys overland has irregular-shaped headlights mounted onto the front fenders. in 1940 when seven-inch round sealed beam headlamps became standard every manufacturer had to change their headlights to meet the standard.
headlight height the height requirement states that the headlamps must be mounted between 22 to 54-inches from the roadway with the vehicle sitting at ride-height, measuring from the centerline of the headlamp. if they are mounted in the fenders or grille area this is already decided for you, unless you decide to exchange them for something from another vehicle. in that case the next step would be to select the type of headlamp to use.
most early hot rods will have separate headlights mounted in pairs somewhere on the front of the vehicle. full-fendered cars usually have stock mounts atop the fenders or into the fenders. fenderless cars have to create a mounting point. this is usually done by using some kind of modified original crossbar or aftermarket frame mount. this is where most of the problems with mounting height are
headlights that are mounted too low and properly aimed will light the area directly in front of the vehicle but not project very far down the highway. headlights that are mounted too high and properly aimed will project far down the roadway in front of the vehicle but provide very little light directly in front of the vehicle.
a recent study indicated that for passenger cars, the general findings have been that, for every one inch the headlamp is lowered, the detection distance is decreased by approximately ten feet. for example, lowering light truck headlamps five inches could result in a loss of fifty feet of forward roadway visibility.
this effect can be demonstrated by walking down a path after dark using a flashlight to illuminate your path. if it is held high the path ahead will be well lit, but the area just in front of you will be pretty dark. conversely, if the flashlight is lowered to about waist level more light will be trained in front of you and down the path. if it was lowered to about your knees and aimed at the same angle as the other positions the ground in front of you would be well lit but down the path would be pretty dark. so proper aiming and mounting of headlights are critical elements in their performance.
center of the headlights on this t-bucket is only 19-inches above the road surface. far below the minimum allowable height of 22-inches. small accessory lights mounted below the headlights also do not meet code for type or location.
Read more: 2004 Jeep Grand Cherokee Headlight Bulb
headlights on this deuce highboy are mounted at 26-inches above the road surface, well over the 22-inch minimum and significantly below the maximum height of 54-inches allowed. these headlights are mounted on aluminum accessory stands like those usually seen on old fenderless hot rods.
these headlight stands are a reproduction of the cut down headlight bar from an early ford that was so popular on post-war fenderless hot rods. they are available from a number of sources such as speedway. headlight shown on the ’32 ford highboy is mounted on these stands and is a reproduction of the gm guide headlights with an auxiliary parking/turn signal lamp on top and amber leds in the h4 halogen conversion, available from united pacific.
original headlight housings with stock innards or conversions to newer high-tech headlamps can be used where a stock appearance is desired. many of the builders of hot rods choose to use the dietz 7-inch teardrop housings, kingbee style teardrops, or gm guide style teardrops with integral parking/turn signal housings on top. other similar shaped headlight housings are available like those on peterbilt big rigs. most of these accept the standard 7-inch sealed beam or many of the alternative units that are designed to replace the original sealed beams.
original equipment and their conversions or the other popular styles are available from aftermarket companies like bob drake, dennis carpenter, speedway, wescott auto and united pacific. included here are a few examples. a wide variety is available on their respective web sites.
these are reproductions from speedway of the original brass headlights often used on t-buckets. they are equipped with halogen xeon bulbs.
these are reproductions from speedway of 1926-27 model-t headlights that are 9-inches in diameter so they are not compatible with standard sealed beams but have been converted to 12-volt.
these are reproductions from united pacific of the original gm guide style headlights that have become very popular because of the integral parking/turn signal light attached to the top.
these are reproductions from speedway of the dietz style 7-inch diameter headlights that have been the most popular choice by those building hot rods for many decades. they will accommodate almost any type of headlamp conversion commonly available.
these are reproductions from speedway of the kingbee style headlights that are 7-inches in diameter but shallower than the dietz style so they might appeal to someone that wants a smaller looking headlight. but they may not be as suitable to use because some of the headlamp conversions may not fit into the smaller backspace.
here are three examples of headlight installations as seen at recent car shows. one shows stock headlights on a 1932 ford, the second one a rare pre-war headlamp popular in the ‘40s and ‘50s and the last one an early ford coupe with headlamps from a modern vehicle molded into the fenders. by searching many of the car events on sites like hotrod hotline you may be able to find just about any application that might fit your project.
the final step in the process is the selection of a headlamp. there are a large variety of choices ranging from the standard sealed beam and halogen sealed beam to more high-tech hid, led and halogen replaceable-bulb headlamps. there are a lot claims made about each type extolling the merits of each one. regardless of the claims the legal requirements set limits as to the minimum and maximum intensity that all headlamps must adhere to.
in north america high beam intensity is now 150,000 candelas (cd) per vehicle, double the nonhalogen limit of 75,000 cd but still well shy of the international european limit of 225,000 cd. these limits kind of level the field between all types of headlamps, so other factors like cost and longevity become the primary factors when making a selection.
these are the markings that you will find on a headlamp that will help in identifying them.
north american sae headlamp lighting function markings:
h sealed beam headlamp
hg gas-discharge (hid, “xenon”) headlamp
hl led (light-emitting diode) headlamp
hr halogen replaceable-bulb headlamp
this is a h-4 halogen bulb and reflector kit for installation in the original 10-inch diameter 1932 ford headlights. it is available from speedway and allows the use of the original style housings with modern day internals.
this is a halogen h-4 type bulb with a blue coating. they are interchangeable with the standard h-4 bulb.
led conversions are also available for installation into many of the housings found on a variety of vehicles. shown here is a unit available from speedway.
because there are so many options to consider when making a selection i have included here a source for detailed information and evaluation of the various type of headlamps from a source with extensive expertise.
daniel stern lighting is considered by many to be north america’s premier automotive lighting consultancy and supply house. mr. stern is an experienced consultant in the field of automotive lighting science and technology, setup, regulation, development, history and modification. his expertise in the field us unmatched by any that i have encountered. he has a unique web site that lists lighting items for sale and extensive technical information about lighting and lighting devices. it’s not a typical shopping cart driven site; you must call and get expert advice on the products that are offered. the following is a small portion of the tech info available there (reprinted with permission) that answers some of the questions we all have when trying to separate the hype from fact about available lighting devices for our vehicles. before deciding which headlamp to order i would first review the technical information available at www.danielstearnlighting.com
dangerous, illegal, blue headlight bulbs – what’s all the fuss?
various companies and individuals are selling halogen headlamp bulbs with blue or purplish-blue glass. there are lots of spurious claims made for these bulbs. they’re falsely advertised as “xenon bulbs” or “hid bulbs”, the blue glass is claimed to “force the bulb to perform at a higher level”, and there are seemingly endless amounts of pseudoscience aimed at enticing buyers who want better performance from their headlamps. in fact, these bulbs reduce headlamp performance while increasing dangerous glare.
how and why are blue bulbs dangerous?
many of them degrade roadway safety,” both yours and other drivers’. some of them can be physically hazardous. here are the nuts and bolts of why blue bulbs are a bad idea: white light is made up of every color of light mixed together. but the colors are not all present in equal amounts. the output spectrum of filament bulbs, including halogen headlamp bulbs, includes a great deal of red, orange, yellow and green light, but very little blue or violet light. blue bulbs have colored glass (or a filter coating applied to clear glass) that allows only the blue light through the filter — this is why the bulbs appear blue. because very little blue light is produced by a halogen bulb in the first place, it is only this very small amount — a tiny fraction of the total amount of light produced by a halogen bulb filament — that ever reaches the road.
blue and violet are the shortest wavelength/highest frequency colors of visible light, and, as such, they scatter the most readily. this is why the sky is blue rather than any other color from the sun’s white output spectrum. blue light doesn’t just scatter most readily in the sky, but also in the eye. to observe this effect, try this informal experiment: next time you see a dark blue storefront sign or a row of blue airport runway landing lights after dark, notice how blurry the edges of the sign or landing light appears compared to adjacent lights or signs of different colors. decades ago, hot rodders would install “blue dots” in their cars’ taillamps. these small bits of blue glass cause the taillamps to appear not red with a blue dot in the center, but rather pinkish-purple, because the observer’s eye easily focuses on the red but has trouble with the blue, which remains out of focus and appears to tint the entire area of the red light.
are these blue bulbs illegal?
us, canadian, european and japanese regulations all call for “white” light. there is no one specific light color that is defined as “white” light; rather, there is a large range of output spectra that are considered “white”, and the “white” light is permitted to exhibit visible tints of blue, yellow, green, orange or red. various regulatory bodies are considering narrowing the “white” standard so that it is less permissive of blue tinting. such has been the spread of blue headlamp bulbs that many police agencies have purchased in-field beam color testers—they use these on headlamps that look too blue to be legally considered “white”.
what about blue-tinted headlight bulbs that i found at a local auto parts store, or on the internet? they’re sold as being “dot approved”. are these legal?
probably not. there’s no such thing as “dot approved”. dot does not “approve” products as the european regulatory body does. rather, the manufacturer of an item of motor vehicle equipment is legally obligated to self-certify that his product complies with all applicable regulations. for some items of equipment, such as headlamp bulbs, the certification takes the form of a “dot” marking on the bulb base. however, there is no legal obligation for the manufacturer to submit his product for government testing before applying the marking, and many companies go ahead and apply the marking even to bulbs that do not comply with the law. the relevant regulations (us federal motor vehicle safety standard 108, canadian motor vehicle safety standards 108 and 108.1, and ece regulations 8, 20, 37, 98, 99, 112 and 113 all call for “white” light, defined as discussed above, so the statement of dot compliance itself is false for a bulb that emits a light color obviously different from “white”.
thinking of converting to hid?
so you’ve read about hid headlamps and have it in mind to convert your car. a few mouse clicks on the web, and you’ve found a couple of outfits offering to sell you a “conversion” that will fit any car with a given type of halogen bulb. stop! put away that credit card. hid headlamps are terrific, and they can offer significant and substantial safety performance advantages over halogen headlamps, but only if they’re designed and built as hid headlamps from the start. installing an “hid kit” in a halogen headlamp isn’t an upgrade; it’s a large and serious safety downgrade.
an “hid kit” consists of hid ballasts and bulbs for retrofitting into a halogen headlamp. kits for replacement of standard round or rectangular sealed-beam headlamps usually include a poor-quality replaceable-bulb headlight lens-reflector unit that’s not safe or legal even when equipped with the intended (usually h4) halogen bulb.
halogen headlamps and hid headlamps require very different optics to produce a safe and effective—not to mention legal—beam pattern. how come? because of the very different characteristics of the two kinds of light source.
claim: “superwhite” bulbs produce 85w of light from 55w of electricity
reality: “superwhite” (“hyperwhite”, “ultrawhite”, “platinum”, etc., basically any bulb advertised as being “whiter” than normal) bulbs produce more glare and less seeing light than standard bulbs.
bottom line: the laws of physics are the laws of physics. they don’t bend even for the highest-paid advertising agency. there is no way to get “85 watts of light for 55 watts of electricity.” tinted bulbs aren’t better.
selecting and installing headlights on a hot rod is a simple three-step process. the headlights have to be installed at a height that projects light down the highway, while still lighting the area in front of the vehicle and not blinding other drivers in the process. depending on the year and model of the vehicle the headlamps may be installed in the grille-mounted housings, into the fenders, atop the fenders, alongside the grille shell, on a fender-mounted crossbar or independently on frame mounts.
for the separate-housing models a wide variety of styles are available from a number of aftermarket sources; some that incorporate the parking lights/turn signals into them. these same sources also offer a number of different headlight stands onto which they can be mounted.
the third and most critical part of the process is the selection of the headlamps. standard 7-inch diameter sealed beam headlamps fulfill the requirements for light output at the most economic price. other, more high-tech headlamps like halogen bulb and led units promise to supply better lighting performance and output, at a price, but by law may not exceed the maximum allowable intensity. so the final choice is driven more by style than performance.