From the April 1956 issue of Sports Cars Illustrated.
So you can’t climb Everest, you can’t have Monroe, and you’re not likely ever to ride a rocket to the moon. But you can, if you’re properly heeled, achieve an experience that’s in the same ultimate class—you can get yourself a Mercedes-Benz 300SL. And if you really respond to machinery, the effect is the same.
After exhaustive road testing of a standard 300SL, after driving impressions in a race-tuned version and interviews with several owners and specialist technicians, I’m ready to haul off and make a flat, unequivocal statement: This is the finest production sports car in the world. No exceptions, no qualifications. On all critical counts, it scores.
As a piece of automotive sculpture the 300SL is a masterpiece. With its “gullwing” doors and its own Teutonic treatment of hippy, organic contours it stands splendidly apart from all the clichés of postwar styling, including the much-plagiarized Italian school. The 300SL is a car that can take first place in a concours d’elegance, then clobber all comers in a tough race. Manifestations of its might are victories won all over Europe and the United States from the world’s best all-out competition sports cars. At the same time it’s a luxury carriage. Sports cars as a rule offer little in the way of comforts and nice refinements. In fact, starkness is part of the stock-in-trade of most sports car builders. But the 300SL achieves the all-weather comfort and the rich finish of fine luxury cars without “engineering compromise”—that rarely-challenged excuse for typical sports car asceticism.
Beyond this, the 300SL is prophecy incarnate. It’s a pace-setter, a style-setter, a design conception that is bound to influence the world’s automotive industry for many years to come. For example, a top Detroit stylist tells me that the 300SL’s roof doors are sure to be copied in the coming U.S. cars because they are the only means of getting in and out of the kind of ultra-low vehicles that the buying public craves. Several Detroit “idea cars” already have imitated this feature.
And styling is the least of the 300SL’s shock treatments to the industry. Gasoline fuel injection (FI), first pioneered on the 300SL, will give the internal combustion engine a new lease on life and probably delay the advent of gas turbines for years. Detroit, aware that FI means instantaneous throttle response, more horsepower, and lower body lines, is already working all-out on injection. At the last count, there were 18 300SL’s in the possession of Detroit manufacturers who are boning up on FI’s secrets.
Another feature that’s bound to be copied is the position of the 300SL’s engine—mounted on its side to lower body lines and the center of gravity. The brakes are novel. While brake diameters in all cars have shrunk to conform to shrinking tire sizes, it took the designers of the 300SL to think of widening the brakes to compensate for the lost friction area. The 300SL has four-wheel independent suspension, a feature of Mercedes-Benz cars since the early thirties. This, too, is being readied on Detroit drawing boards. Even the intricate and expensive trapezoidal frame may be adapted to automation’s techniques. Literally, the 300SL is a car of the future that can be possessed today.
All 300SL’s are not necessarily alike. The standard package that you buy across the counter costs $7463 at U.S. port of entry. It’s a magnificent performer, with dazzling acceleration and a top speed of nearly 140 mph. But there are many performance options. It’s beautifully, finely finished, but there are many finish options. The result is that although you can get a 300SL for under $7500, few are sold for less than $8,000 after licence [sic] fees, taxes, and options have been added. And if you want a 160-mph, all-out competition 300SL you can invest $10,000 or $11,000 with no difficulty. But don’t get the idea that the pin-money 300SL is anything less than a going bomb.
The fire engine red, strictly standard model that I first drove came to my door equipped with meister mechaniker Robert Leutge, an expert technician sent to the U.S. by the Mercedes factory to train agency mechanics. He tossed the door up, slid over to the passenger’s side, and I entered.
With the 300SL this is something of an art and it varies according to build, sex, and dress. For the first or fiftieth time it’s a thrill. Actually, the car is not a handy package to climb in and out of but the mild gymnastics involved are a small price to pay for what you get. The somewhat limited entry area provided by the roof doors is dictated not by the car’s lowness alone, but also by the extreme depth of the light, rigid, “three-dimensional” tubular frame. When you sit in the car your elbow rests on the door sill, which is wrapped over the top frame members. To simplify entry and exit for the driver, all 300SL’s are equipped with a steering wheel that can be folded under the steering column. Also, although the steering column is not adjustable, you can have your choice of two different column lengths.
The doors can be locked from the outside by the conventional method. To open them, you press a slightly-protruding cam which exposes the door-handle. Give this an easy outward and upward tug and the door floats up to its full-open position, aided by springs that give just the correct amount of counterbalance. The door must be slammed hard to be closed and this produces a loud, jarring thud. On the inside door handle of every new 300SL is a somewhat disquieting notice urging that doors be locked from the inside to guard against their opening spontaneously at high speed.
When you’re seated in a 300SL you know you’re in. You’re practically encapsulated. You feel very much a part of the car, as you should be. Visibility is good. Straight ahead and just below eye level are a big tach and a big speedometer. There are plenty of other instruments and controls and they take some time to learn.
The first thing I noticed was the low mileage registered on the odometer—significantly below the 1000-mile break-in period recommended by the factory. But Leutge put me at ease.
“You don’t have to worry about winding up these engines,” he said. “Before they’re even dropped into a car they’re run for 24 hours on a dynamometer, including six hours at peak output. Then they’re torn down, checked, reassembled, and given another eight hours of running-in. Our times may be a shade slow, but don’t be afraid to peak it in the gears.”
The tricks of firing up a fuel-injection car are few and simple. For cold starts you pull out what corresponds to a choke and for hot starts you pull out a different button—that causes a whining, high-speed pump to go to work in the fuel tank. It not only purges vapor pockets from the fuel system when hot, but also makes available a two-gallon reserve fuel supply. The factory recommends that the extra pump be used continuously during high-speed operation.
This is not one of those engines the existence of which its makers have spent millions to hide. It explodes into urgent, buzzing life, idling at a busy but smooth 750 rpm and every fiber of the beast is ready to charge.
The 300SL has positive syncromesh on all four of its forward speeds. You thrust it into first, simultaneously punch the throttle and release the clutch and, in a number of seconds only slightly greater than your reaction time, peak at 40 mph. The sensation of catapulting acceleration is unforgettable. Second, again with tremendous G’s, propels the car up to the high 60s in scant seconds more. Third is a wonderfully useful ratio with terrific dig from about 9 to 96 mph.
The torque of the little 3.0-liter engine is fantastic and it’s hard to see where it all comes from until you remember that the injection system is pumping fuel into the cylinders at a constant rate that carburetors cannot match. Fourth gear, with the standard rear-axle ratio, gives smooth, continuous acceleration from 15 to 140 mph! It is thoroughly adequate for city traffic and even for pulling fairly stiff grades. For fierce acceleration and fast hill-climbing, third meets nearly all requirements. During our shakedown tests among the steep peaks and canyons of the Santa Monica mountain range, we had to resort to second cog only on the very steepest grades, and then we flew up to them. As for first gear, you should always use it when starting from a standstill. Beyond that you just keep it in reserve for pulling stumps and for competing in the Alpine Rally.
There are tricks to driving the car. Its steering, with less than two turns from lock to lock, is definitely heavy and has a wonderful feel. The steering gear itself is of the no-backlash recirculating-ball type with hydraulic centering. The brakes are magnificent and indestructible, and they’re vacuum assisted. But they don’t lock the wheels at a touch, Detroit power-brake style. They demand some muscle power, and so do the clutch and the shift lever. In the 300SL, driving is not the near spectator sport it has largely become in this age of robotized motoring.
Minimum muscular endowment is required for the comfortable operation of the 300SL. Caution and sound judgment, however, are essential to the continuing enjoyment of this or any other high-performance car and even a small error can have very discouraging consequences. For example, I had read in both a British and an American road test that the car should be pushed through turns under power, actually steered with the throttle.
As we approached our first tight corner I mentioned this to Leutge. “No—No!” he cried. “Do that and the rear end comes swinging around. With these pendulum axles you have to be careful. The oversteer isn’t much if you have competition springs, but with standard springs you must watch it all the time.”
At this point I asked Leutge to demonstrate proper fast-cornering technique with the 300SL and he took the wheel. He popped his gear changes with a smart, hard style and reached his desired speed of entry into the turn. All the way around the curve he maintained neutral acceleration, just patting the throttle lightly and occasionally to keep his velocity constant. As the curve began to straighten out he stomped the throttle to the floorboards, rocketing into the straight. Further checking with men who have driven 300SL’s in competition verified this as the one-and-only technique for keeping out of trouble during high-speed cornering. With this car you do not horse around with throttle steering.
During the very hardest cornering there is no perceptible body roll and you feel an unusual sense of security. This is added to considerably by the car’s phenomenal brakes which are fade-proof and provide uncanny stopping distances. The adjustable bucket seats give excellent support against sideways motion. There’s a remarkable absence of wind noise in this car, even at 138 mph, but otherwise it is by no means a silent servant. The auxiliary fuel pump, used constantly at high speeds, emits a nervous whine at the driver’s back. The indirect transmission gears have a loud, vintage buzz. These sounds are more or less musical to the enthusiastic ear. Less so is the peculiar, harmless clunking noise that originates in the rear axle mechanism of these cars when some, but not all, left turns are made.
The coil-spring four-wheel independent suspension gives a ride that is surprisingly soft. The cornering feel in particular is quite different from that of a fast, solid-axle machine and is hard to describe. In place of the sensation of unyielding chassis “bite” on the road there’s a softness to the 300SL’s cornering grip: You do not feel as though you’re on rails; you know damned well you’re on rubber tires. The bite is tenacious all right, but not harsh. Barreling full-bore down a straightaway, the car never feels as though it’s becoming lighter. At top speed it still squats like a stalking cat and its traction under all conditions is pretty unbeatable.
So far, we’ve been talking about the basic 300SL “economy model” with a touring-car camshaft. With this setup the output is 220 horsepower, the engine idles at 750 rpm, and the torque characteristics are quite uniform throughout the engine rpm range. This combination makes for one of the most thrilling rides of your life. That is, until you experience a 300SL running the hot, competition cam.
With this one modification the car acquires an entirely new character. Now it peaks at 240 horsepower—a figure incidentally, which other road tests have mistakenly associated with the standard model— and it idles at 1100 revs. In the lower engine-speed range it is slightly rougher and it neither adds to nor subtracts from the vehicle’s performance. It’s in the higher rpm’s that it makes another car of the 300SL.
Lance Reventlow of Hollywood is the devoted owner of a 300SL with the racing cam and all the other performance options. His car has heavy-duty springs and shock absorbers, Rudge wheels, an assortment of rear-axle ratios and special racing tires. It also has one of the all-aluminum bodies that the factory has available. The light body represents a weight saving of about 350 pounds and Reventlow’s car represents an investment of well over $10,000.
Lance introduced me to the delights of this rarified form of motoring with a demonstration of the effect of the racing cam. “Watch this,” he said, as he dropped into Third at about 2000 rpm and bore down on the throttle. The tach needle rapidly climbed past 3000, then 3500. I watched and waited. Then at 3600 all hell broke loose. The car, already accelerating as few cars in the world can do, took off as though JATO units or a second engine had been cut in. Beyond 3600 the acceleration was appalling. It was like being pulled forward at fantastic speed at the end of a powerfully-drawn cable. Oddly enough, the last time I had experienced that precise sensation was at the wheel of a 7.1-liter, supercharged Type SS Mercedes-Benz built in 1930.
Reventlow stayed on the throttle until the tach hit 5500 and the scenery was a blur. The inexorable torque stayed the same, according to the hard pressure on hips and shoulders, until he backed off. In the “mild” range again, he slowed to 15 mph, then pulled away strongly in top gear. “That’s what I mean,” he said. “It’s really two cars in one. One is a lamb and the other is a raging lion. And you can turn them off and on with a touch on the throttle. You can putter around town for a year and never call on the fierce side of the car’s dual personality. But the instant you want that real wild performance, it’s there.”
The competition springs and shocks give this car a far firmer ride and cornering bite. The Rudge disc wheels, which cost $350 per set, add 25 pounds to the car’s weight. But they’re essential for long races in which tire-change stops are critical. This car has won both concours and races.
One of its recent race wins was at Torrey Pines, with Bruce Kessler at the wheel. Other cars in the full entry list at Torrey could be heard for miles as they blasted around the course. The fact that the obviously competent 300SL ran a muffler and purred its way to the checkered flag without pyrotechnics impressed many spectators. M-B’s West Coast sales manager tells me that during the week that followed, 11 300SL’s were delivered to individuals who said they were sold at Torrey Pines.
One of the main contributing factors to the long string of 300SL racing victories is its frame, which is unlike that of any other M-B production car. The complex network of small-diameter tubes is erected in such a way that the tubes are subject to push-and-pull stresses only, and not to twisting stresses. This torsional stiffness has an all-important effect on keeping suspension geometry uniform and that, in turn, has a decisive effect on roadholding. The tubes are everywhere—above the engine and in the passenger space. The frame is made mainly by hand and its appearance in large-scale production is not likely.
The real guts of 300SL performance, of course, lie in its engine, which is a remarkable blend of radical and conservative design features. On the conservative side are the cast-iron block, the single overhead camshaft, the NOT vee-inclined valves, the far from straight-through porting, the moderate compression ratio. This last, nominally 8.55:1, varies with the individual engine and the actual ratio is stamped on the cylinder block, just under the name plate. The compression ratio of our standard test car was 8.28:1.
On the radical side are the offset, inclined engine mounting position, and the unusual combustion chambers which do not extend into the head at all but are contained entirely within the cylinder block. The head has a perfectly flat lower surface and immense valves for a small engine; the intakes measure 1-5/8 inches and the exhausts are 1-15/16. Most radical of all, of course, is the fuel injection system.
The 300SL’s crankshaft is cradled in seven main bearings. The short, H-section connecting rods are ground to a smooth finish. A passage up the center of the rod carries oil to the wrist pin. The heads of the full-skirted pistons are slightly wedge-shaped and they constitute an unusually functional part of the combustion chamber. Each piston carries three compression rings and one oil ring.
The single overhead camshaft rides in four bearings and has a large vibration damper at its forward, sprocket end. According to my factory informant, the standard 300SL camshaft is identical to that used in the Type 300S touring machine. A number of people have wondered what effect fuel injection has on valve timing. Evidently it has none.
The lobes on the 300SL’s camshafts have a fast high lift and very sporting duration and overlap characteristics:
Inlet opens: 11° – 20°
(Before top center)
Inlet closes 53° – 58°
(After bottom center)
Exhaust opens 36° 30′ – 56°
(Before bottom center)
Exhaust closes 10° 30′ – 18°
(After top center)
Cold-engine tappet clearances are .002 ins. for the inlets and .008 for the exhausts. For an overhead-cam valvetrain, the 300SL’s is quite silent in its operation.
A point of considerable interest to the engineering fan is the more than slight resemblance between the 300SL engine and the basic engine that powered the immortal Types K, S, SS and SSK Mercedes of the Twenties and early Thirties. Dr. Porsche designed the old single-cam six with its eerie-sounding Roots blower. The ultra-modern Mercedes six looks much the same under its cam cover. The staggered valve arrangement is the same and the cam-follower layout is almost identical. It’s also interesting that the acceleration effect that Porsche obtained with a costly and complicated supercharger has now been duplicated and surpassed by means of the 300SL’s racing camshaft.
With the fuel-injection system, an assembly of six small plunger pumps delivers atomized gasoline directly into the cylinders, at a pressure ranging from 568 to 682 psi. Air alone is drawn through the inlet valves and the mixture of fuel and air takes place within the cylinders. The timing and the amount of each shot of fuel is regulated automatically and precisely. Filtration of both air and fuel is far more critical than in carburetor engines.
You might expect maintenance of the system to be extremely tricky, but it’s not. The air filter requires cleaning every 2500 miles, the fuel filter every 15,000. The fuel-feed system compensates automatically for changes in altitude and temperature. On the throttle body in the air-intake manifold, there are a couple of adjusting screws for regulating idle speed and mixture richness. They can be adjusted with a small coin. And that’s all there is to it.
One idiosyncrasy of the system is described in the owner’s manual. “It may happen with the injection engine that after stopping the engine will turn a few backward revolutions. This does not necessarily indicate a defect. Engage a gear in this case and stop the engine by clutching.” And another precaution: to stop, “turn the ignition key to the left while idling. Do not on any account try to stop the engine at a higher speed than the idle running one.” I assume that violating this rule results in de-lubrication of the cylinder walls by powerfully-injected raw fuel.
Checking with many 300SL owners (at this moment there are 171 who have bought cars through the West Coast distributor alone) I have been unable to find any complaints against the reliability of the injection system or, for that matter, of the car as a whole. A mechanic who specializes on 300SL’s assures me, “You just drive the car— it takes terrific abuse and gives no trouble. We used to have one chronic complaint and that was about spark plug failure. Now we recommend platinum-point plugs and have no more of that trouble.”
When you consider what it must cost to produce each of these cars—all the handwork, expensive components, quality— it’s hard to consider the 300SL as anything but a bargain at the base price of $7463. And this includes a splendid set of tools, power brakes, hinged steering wheel, optional steering columns, clock, heater, an exhaustive maintenance manual, a parts catalog, minutely detailed instructions for the servicing of the car for its first 62,500 miles, and many other bonus items.
Actually, you can buy the basic 300SL for $6900 at the factory in Stuttgart, Germany. Transportation cost and import duty then become your responsibility. However, if you bring the car to the U.S. within six months of purchase, the factory refunds $1300 to you, which offsets the freight and duty expenses and then some. With large parts inventories in several American cities and with an excellent, factory-supervised service organization, it’s just about impossible to duplicate what the 300SL has to offer at any price.
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