Precision Autoworks was founded by Bob Platz in 1978. It specializes in investment grade restoration of German cars, mainly for either high quality street use or national show competition.
We stress the importance of authenticity in which the paint color, parts, body design, and options reflect what could have been ordered at the time for the model and chassis number of the car.
A review of our track record includes major wins at Amelia Island, Hilton Head, Radnor Hunt, Mercedes Club Nationals, 190SL Club Nationals, AACA Hershey, Greenwich, Ault Park,
Euro Auto Festival, Winterpark and Meadowbrook.
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The 300SL Story by Bob Platz
As with most traditional collectibles such as early American furniture, European porcelain, Impressionist paintings and antique Persain rugs, most classic cars are valued by pristine condition and authenticity. If you already own a Mercedes 300SL or have an interest in buying one, feel free to reach out to us via phone or email. The 300SL story, contained therein, provides a useful guide on how to achieve that goal. Too many cars are restored without a serious regard for authenticity, thus negatively impacting their potential value.
THE 300SL STORY BY ROBERT PLATZ
MERCEDES AND RACING
The inseparable and often rocky marriage of Mercedes and racing had its start at the beginning of the 20th century when Emil Jelllinek, an entrepreneur of the first order, successfully challenged Daimler to build him at his expense a new car of superior power to its competitors that he could promote and sell via races on the roads of France. Anxious for the business, Daimler complied with a new in house design created by Wilhelm Maybach and delivered a 4 cylinder 35 Hp car, now aptly named Mercedes after Jellinek’s daughter. This 1901 model had a pressed steel frame, a honeycomb radiator, and could operate at variable speeds. Skeptical at first and at about the same time frame, the Benz company soon saw the merits of sales through racing and for the next 25 years before their merger in 1926, both firms produced very successful grand prix and sports racing cars as in these examples:
1908 Mercedes sports 2 seater 15/20
1915 Mercedes Knight 25/65
1921 Mercedes sports car 28/95
1913 Benz sports runabout 16/40
1915 Benz sports runabout 39/100
It was in the 1920’s that the German economy was hemorrhaging from inflation. With limited funds the newly merged Daimler Benz AG miraculously launched a new series of exceptional sports racers (S, SS, SSK, SSKL) which proceeded to dominate the European racing community until 1934. These cars had been developed from their conventional 6 cylinder touring car that was in production with the K motor. With hardly a pause DBAG with its newly developed supercharger entered the Grand Prix circuit in the early 1930’s first with the W25 and its variants, followed by the W125 and ending their competition in 1939 with Alfa Romeo, Delahaye, Maserati, and especially Auto Union using the W154 and W165.
THE BIRTH OF THE 300SL
The War that followed crippled the operations at Daimler Benz, but as been shown throughout the years, the men at the Mercedes “rennabteilung” would not accept defeat. Now with Rudi Uhlenhaut as their leader, this dedicated team was inspired to act having witnessed the 1951 Le Mans performance of the XK120C Jaguar. Just like the Mercedes S, this Jaguar evolved from production. Once again Mercedes had to rebuild its image and as before with limited resources. Hence they were emboldened to regain their prewar status by building a sports racer using the new three liter production engine. Frankly, their vision for a new Grand Prix car was simply not in the budget at the time.
With Uhlenhaut spear heading the effort, the racing department was able to raise the power of this engine from 115 Hp @ 4600rpm to 171 Hp @ 5200rpm. Moreover it was financially expedient to incorporate the rest of the 300 sedan driveline, steering and brakes with minor changes in consideration of the smaller wheelbase and added power. Now came the biggest challenge. If this assembly was coupled to a chassis of prewar design such as used on the 1939 W154, it would not be racing competitive. They needed a strong chassis but one of much lighter weight. The weight saving tubular frame concept was not new. It had been adopted in principle by Aston martin, Cisitalia, and also the jaguar XK120C. Similarly Veritas had fashioned a trus design. So Mercedes saw an opportunity here. Quite familiar with aircraft construction from the War, their research department designed and built a complex system of tubes to produce the necessary strength in the chassis with only longitudinal forces on the tubes and without bending or torsional movement. In the process they had to make room for the engine and to maintain rigidity, the cockpit had to be deep thereby raising the side walls excluding conventional doors and leaving entry essentially through the roof. Fortunately for Mercedes, the racing rules of the day did not limit the competition to side opening doors. With this new approach, Mercedes had met their objective and saved 45 pounds using the new tube frame chassis as opposed to the prewar ladder type oval frame. Furthermore, when it came time to add the body, they realized that the car should be a coupe with styling similar to Alfa Romeo, BMW, and Porsche, and with low drag. The engine therefore was inclined 50 degrees to the left and the hood lowered producing a drag coefficient of .25, a very good result.
And so the W194, the 300SL sports racer, was born and successfully raced in 1952 almost winning the Mille Miglia. Kling came in second due to a brake failure. Yet they won Berne, Le Mans, and the Pan America Mexican road race.
THE PRODUCTION GULLWING
In 1953 life now became more complicated for Mercedes. They were anxious to get back into Grand Prix racing with the new 2.5 liter formula set for 1954. But with the success of the 1952 racing season using the W194, they envisioned new ways to improve the car. First of all the engine was fed via triple Solex carburetors and a change to Webers with a test bed engine showed measurable horsepower improvement. And then there was direct fuel injection that had been in the experimental stage since the 1930’s. By 1936 high compression diesel made it into the 260D automobile. However, gasoline fuel injection remained a problem due to high heat and vaporization issues. Secondly, wind tunnel testing revealed that high pressures built up in the engine compartment effectively slowed the car at high speed and by using side port venting, this air pressure dam could be relieved thereby yielding more effective use of the engine’s power. Thirdly, since the prewar days and again on the 300 sedan the dual jointed axles attached to the rear differential provided an independent suspension but also tended to produce excessive camber movement which effectively lifted the rear wheels and a margin of power was lost. A new single low pivot swing axle with a compensating coil spring had been in the works for the new 220 sedan. It would have to be redesigned and strengthened for use in the race car.
While Mercedes management vacillated over their future course of action, a totally new development presented itself embodied in the person of Max Hoffman. He had just been named the sole distributor of Mercedes vehicles in the United States, and had become enamored by the W194 and its commercial development as a production car. He backed his interest in a firm order of 1000 cars. Just like 50 plus years earlier with Emil Jellinek, Mercedes saw a business opportunity that would add to their prestige as an automobile manufacturer. They never dreamed of this course of action for their 300SL sports racer. But money talks, and all efforts were now applied to converting the W194 into a production car. Some creature comforts were added of course. It was fortunate that Mercedes continued tests on fuel injection with their aircraft engines and a chance relocation of the fuel injectors from the head to the block and pointing away from the spark plugs that enabled the Bosch fuel injection system to be incorporated into the production car. Vaporization was still a concern and so a second electric pump was added at the gas tank. Moreover, side venting made it into the new design, but not the low pivot swing axle. It had to wait. Actually the first prototype car as shown in February 1954 at the New York Auto Show was still “a work in progress”. It took a few more months before production could begin.
It is interesting to note that this is a rare instance that thanks to Bosch fuel injection replacing the triple Solex carburetors, we have a production car somewhat competitive with its racing car parent. All Mercedes cars are normally subject to changes over the timeframe of production, and in this case for the gullwing from mid 1954 through mid 1957, thereby completing 1400 units. The chassis designation for this car is W198040.
300SL GULLWING MODIFICATIONS
Since authenticity has become a vital component to both show competition and value, I have identified some of the more significant changes by chassis number in calendar order.
Chassis no. Description
4500033 Cold start thermostat installed
4500039 3.64 rear replaces 3.42 as standard
4500041 Rear brake cylinder size 1 1/16 replaces 1 1/8
4500051 Gooseneck shifter to remote straight shifter
4500056 Shielded motor housing for the electric pump
4500076 Fixed transverse engine tube to removable one
4500100 (circa) Radiator bugscreen sq. holes to diamond
4500148 Door seal profile change
4500152 DB steering replaces ZF
5500050 (circa) Deep shoulder radiator cap 80kPa to 100kPa
5500075 Rubber grommets for hood rod added
5500076 Front bumper guards from square profile to round
5500082 Locking safety hook for hood redesign
5500096 New steering damper replaces removable ball pin type
5500106 66mm exhaust pipe replaces 68mm
5500148 Oil pressure line redesign
5500154 2 piece vacuum line from mixture controller to injection pump replaces 1 piece line
5500155 6 in. treadle vac replaces 5 ¼” plus brake pedal change
5500161 Rear bumper guards from square profile to round
5500179 R3 injection pump replaces R2
5500212 Eyebrow welting changes to leaded seams except on alloy bodies
5500212 (circa) Leather or MB tex rug binder to cloth type on floor
5500212 (circa) License light under layers are omitted
5500217 Rocker molding end L brackets replaced by T screws
5500217 Front rocker covers may have become optional
5500217 Cross pieces (wings) for front grille modified
5500317 Crankshaft markings on damper with indicator on block
5500351 Courtesy light switch moves from header to door hinge
5500351 (circa) Headliner change at A and B pillars to door sill upholstery
5500354 Treadle vac brake assist to ATE T50 booster
5500354 Suspended gas pedal to floor mounted one
5500354 (circa) Black engine backing plate gasket goes grey
5500419 Spare tire holder for bolt on wheel redesign
5500520 One piece ashtray replaces unit with exchange cup
5500570 Front fender louvre trim T screws replaced by sheet metal screws
5500771 Wind up clock to electric
6500023 Concave star grille to flat star grille
6500031 Metal caps added to wheel cylinders
6500045 Distributor modification, no vacuum
6500078 Duplex oil pump to outside oil pressure pump
6500078 External oil pipes at block replaced by flex lines
6500098 Vent holes with optional covers added to front brake anchor plates
6500107 Vent holes with optional covers added to rear brake anchor plates
6500196 Single point to dual point distributor (sport cam)
6500303 Single point to dual point distributor (standard cam)
With the production gullwing launched, Mercedes could finally refocus from development to delivery of their grand prix race car. Having built their reputation on the W194 300SL racer coupled with the marketing of the W198040 cars, the new game plan was to dominate sports car racing and grand prix racing essentially with the same car from a technical point of view. That said, the new grand prix car had the factory designation of W196 with a 2.5 liter engine and the sports car became the W196S, soon to be nicknamed the 300SLR. It sort of looked like a gullwing and the engine had the same 3 liter displacement, but that was the end of their similarity. Both the W196 and the 300SLR had 8 cylinders, desmodromic valves (actuated by gears instead of springs), a five speed gear box, in board brakes, 4 wheel independent suspension, a tubular chassis, a low pivot rear swing axle, and direct fuel injection. Aside from bodywork the only real difference in the two cars was in the engine. Aside from displacement, the 2.5 liter engine had forged barrels welded together in 2 groups of four with water jacket covers on the side blocks while the 3 liter 300SLR engine had a similar layout with all aluminum castings. Both had a 10 main bearing crank. To achieve the displacement increase for the 300SLR, the grand prix engine was bored out from 76 to 78 mm and stroked 68.8 to 78 mm. With similar streamlined bodywork, Uhlenhaut could go faster in the 300SLR. Needless to say these cars were hard to beat. In fact the 300SLR never lost a race until it was withdrawn at the time of the Le Mans crash in 1955.
THE PRODUCTION ROADSTER
Retiring from racing, Mercedes decided to take care of “unfinished business”. They never planned to turn the W194 into a production car. The Bosch direct injection and certainly the gullwing doors were not all that user friendly. Combining this situation with the double jointed rear axle on a powerful sports car they saw as trouble in the hands of the general public. Furthermore, by 1955, the USA dealers were clamoring for a convertible. The first thing Mercedes had to do was to figure out how to modify the space frame to accept conventional doors. In addition they wanted to make room for the low pivot swing axle unit including the compensating spring, as well as some luggage room. So the space frame was largely unchanged from the windshield forward with all the modifications done through redesign of the rear. The Bosch fuel injection system was improved with a better fuel check valve at the electric pump; the mixture controller was redesigned; a damper cage was added for additional fuel stabilization; and the injection pump went through internal changes from R3 to ultimately R7. Hence Mercedes kept the basic system. Fortunately, the rear axle change to the low pivot type had already been proven on the W196, and therefore was readily incorporated. To complete the nuances of this new roadster with chassis designation W198042, Mercedes added a glove box, roll up windows, adjustable seat back rests, back up lights, an external fuel filler flap, and a laundry list of amenities found on their regular 300 series sedan.
So what was the cost of all his gentrification? It was about 200 pounds. To overcome this hurdle, Mercedes offered the same 5 rear axle ratios as used on the gullwing, but where the standard rear on a gullwing was 3.64, the roadster standard was 3.89. The optional sport cam (NSL) on the gullwing was made standard on the roadster. The distributor was altered from a dual point single coil system to a dual point dual coil system thereby raising the dwell to 86 degrees. The wheels were widened from 5.0 in to 5.5 in rims. Finally Mercedes offered a light weight version as a factory delivery without bumpers and with covers for the body openings. An additional 15 Hp could be requested with high compression pistons (9.5 to1). Now the factory considered the two models close in performance.
As with the gullwing, rallye equipment was available at special request. The hardtop became available by mid 1958 and if previously ordered, was retrofitted to the earlier cars. The Rudge wheel option with 5.5 in rims (gullwings had 5.0 in rims) was limited to 1957 due to a change in the German law for safety considerations. Leather upholstery was standard on the roadster (it was optional on the gullwing). Similarly the outside left fender Talbot mirror was standard on the roadster. The gullwing mirror was a goose neck with round mirror head, and it was optional.
THE 300SL ROADSTER MODIFICATIONS
As with the gullwing, authenticity remains a crucial element of the roadster’s persona. I am listing some of the more relevant modifications.
Chassis no. Description
7500037, 38, 62 Steel boot cover, aluminum quarter skirt trim extends over exposed screws, various
(pre production) custom interior trim (later modified)
7500081 Leather upholstery std, sports cam std, 3.89 rear std, conv/hardtop combo, padded
(1st production roadster) dash, single low pivot rear axle, bumper guards std, reinforced hood shape and thicker gauge metal, instrument cluster, glove box, perforated seats for ventilation, wider wheel rims, dual points and coils for 86⁰ dwell, longer 11” wiper blades, stronger wiper arms, usable trunk space, crank windows, built in fog lights, better location of emergency brake, reverse lights, larger tail lights, tuned exhaust tip, standard (Talbot) rear view mirror, improved crank case ventilation, exterior fill gas tank flap.
7500180 Wiper linkage coupling between cranks changes from an elbow rod to a straight rod
7500250 (circa) Trunk back wall spacers added to position the suitcases
Dash vent hole escutcheons added
Door sill anodized trim added
Removable boot cover, using sockets and pins, replaces non removable cover with fixed hinges
Optional hardtop can be ordered for future dealer installation.
7500581 Self canceling directional added (USA)
7500581 (circa) Right exterior door lock added
Right interior door light switch added
7500685 Hood locking unit is modified
7500685 (circa) Trunk lock housing changed from gullwing type to
Roadster with extended tab
Trunk lid 300SL emblem changes from the GW clear field to a serrated field
8500047 Front fixed brake shoes to floating (“vintage racing”)
8500080 By pass air shut off solenoid added to mixture controller
8500095 No nut wiper arms replaced by small nut type
8500095 (circa) Deep shoulder radiator cap to shallow shoulder
8500115 Wiper motor becomes 2 speed
8500115 All 3 wiper cranks are reinforced
8500123 Damper cages added to feed and return fuel lines
8500150 (circa) Hardtop option via factory installation initiated
8500200 (circa) Rear quarter panel reflectors added (USA)
Earlier chassis number cars sold later in 1958 in the USA will require reflectors as well (dealer installed)
8500202 Perforations added to seat pleats
8500262 Hinged door armrests to fixed type
8500262 (circa) Rear flange on rockers changed wide to narrow
Rear quarter dogleg exterior accent added
8500302 (circa) Instrument red pointers change to 2 tone
8500340 Transmission gear change
9500001 Rear dogleg heat insulation added
9500001 (circa) Door lock fascia: gullwing style to late roadster
9500078 Wiper activation switch on foot pump modified
9500078 (circa) VDO yellow water bag drops “schriebenwascher”
002450 Plastic liner added to fuel tank
002458 Metal brake can fluid reservoir replaced by small plastic unit
002458 (circa) Small nut wiper arms are replaced with big nut wiper arms
002514 Three pipe to four pipe cooling water system
002514 (circa) Conv. top corner snap added to boot end trim
002634 Bullseye headlight lenses replaced by asymmetric lenses ( non USA )
002780 Four wheel disc brakes replaced the vintage racing brake set up
002780 (circa) Fine grain Roser leather transitions to coarse grain Roser leather
002860 Steering column lock added
002954 Big plastic brake reservoir replaces small plastic container
003010 Chrome dash control levers to black plastic
003049 Alloy engine block replaces iron block
003090 (circa) Rectangular seat perforations change to square
THE COLLECTABLE 300SL
Interest in the 300SL has never waned. It is a part of history that arrived in postwar Europe and the USA when the economies were on the mend with no armed conflicts and there was a positive attitude that the future would be bright. So the 300SL is really more than a car, it is a symbol of what dedication and hard work can accomplish. The values of these cars today are a reflection of the uniqueness of this time period. It is one that would be nice to revisit in our troubled world of today. I leave you below with my current analysis of the market.
AUGUST 2020 300SL VALUATION CHART
Values are based on actual sales and auction results extrapolated to condition 1 cars judged perfect by Pebble Beach standards using the following criteria:
A. Authenticity: all parts and details correct by the chassis number
B. Condition: combines both cosmetic and mechanical components
C. Field Impact: combines color combinations and both factory and period options
D. Provenance: important history and significant ownership
E. Options: have to be period correct and preferably available by the factory when the car was ordered
including the paint color
Dates Production Description Value Guide
1. 1954-5 10 W196S-300SLR (8 cyl. sports racer) $75 million
2. 1954-5 14 W196 (8 cyl. Grand Prix) $50 million
3. 1952-3 11 W194 (6 cyl. 300SL racer) $30 million
4. 1955-6 29 W198043 (alloy body gullwing) 5.5X
5. 1962-3 210 W198042 (alloy block roadster) 1.4X
6. 1957 28 W198042 (rudge wheel roadster) 1.3X
7. 1954-7 1371 W198040 (standard gullwing) 1.2X
8. 1957-62 1620 W198042 (standard roadster) 1.0X
1. Most cars, even if restored, are in reality by this definition probably in condition 3, thereby losing a third or more of a condition 1 value as if judged at Pebble Beach standards.
2. Certain cars may individually have features of unique value. For example 198040-4500028 is the only plastic bodied gullwing.
3. Cars listed above as numbers 4,5,6 have to be original build sheet examples
4. There are no comps for the 300SLR so it is priced at the top of the Ferrari GTO market.
Chassis number 9 was never completed by the Factory, Chassis no. 5 was destroyed at Lemans.
Chassis numbers 7 and 8 are the Uhlenhaut coupes. One might assume that chassis no. 4 (mille miglia 722) is priceless and a value of $100M may not be enough. Nevertheless for the racers (nos. 1-3 in the chart), there are insufficient sales to establish a market and so the values are estimates based on similar cars of other marques.
5. Since the general 300SL market fluctuates, I have chosen to present their values on a sliding scale assuming all variants are at condition 1. Giving the standard roadster a value of 1.0X, the standard gullwing would have a value of 1.2X (20% increase); the rudge roadster is 1.3X; the alloy engine roadster is 1.4X; and the alloy body gullwing is 5.5X. Add .05X for each option: original rudge wheel GW, roadster factory hard top, and original Baisch or Hepco suitcases. For Example, a 1962 alloy engine roadster with factory hard top and Hepco suitcases would be valued at 1.5X.
Mercedes Benz Persononwagen by Werner Oswald June 1986
Mercedes Benz 300SL by Jurgen Lewendowski 1988
Mercedes Benz 300SL Roadster Spare Parts Lists Edition A (August 1957), B (June 1961), C (March 1963)
Mercedes Benz 300SL Spare Parts List Edition C (May 1956)
Mercedes Benz 300SL Coupe Register, Edition 2 by Eric LeMoine 2012
Mercedes Benz Vom Rennsport zur Legende, Motor Klassik Edition, May 1999 by Michael Riedner und Gunter Engelen
Radnor Hunt Concours d’Elegance Program Book, The 300SL Story by Robert Platz, 2016