ROAD TEST

January 1971

Mercedes Builds a Reluctant Racer

Jerry Sloniger


Is a Mercedes 300 SEL 6.3 the ultimate racing sedan? One sometime Finnish race driver thinks so. He recently payed more than double a ''standard'' V-8 price for the only works-built, racing Mercedes in private hands.

Actually his special toy cost over $60,000 because Finland lays a 140% tax on "luxury" imports. It would still cost you or me at least half that to duplicate below the Midnight Sun. That is assuming Mercedes would even build another one.

Drive any 6.3 and you can't help but muse on competition potential, bulk apart. A young Daimler Benz engineer named Waxenberger had the same twitch. His self-styled "hobby" soon grew into a hot sedan he ran personally in Macao where he won. It was hardly the majors but he had proved a point

The next stop was Spa and real racing. Mercedes snuck into town last year like the circus, dogged by a world-wide press, and decided a new tire-slicing surface would reduce safety margins below good odds. So they went home unraced. in part because the FIA wouldn't accept wider wheels at the last moment.

Since then rim-width rules have been eased. "for safety", with a four-inch limit on fender stretching. That decision came largely through Waxenberger's prompting. Meanwhile DB was left with all those meticulously prepared race sedans. They were never raced or rallied though they had indeed covered the equivalent of three or four 24-hour bashes in secret before a Spa entry was even filed.

Thereafter in 1969, Stuttgart with typical thoroughness put better than 10,000 additional race-speed miles on these cars around seven European tracks picked because they also happen to be sites of yearly manufacturers sedan championship races and which are tracks you can rent exclusively. A basic of the Spa slip was their inability to close public roads there for pre-race assessment.

Thus DB was hardly inexperienced when a Finn with this bag of gold the size of Lapland conned them into building a replica. The fact that he would run it largely beyond the ken of most race reporters may have helped his cause too.

And that's how I came to do a few laps in a full-house racing sedan beneath the three-pointed star. I simply happened to be in Finland. They have two tracks there and fortunately the 6 3 was found on Hameenlinna, the most fascinating by far. It might be compared to a berserk roller coaster but it sure wrings a car out quickly. In truth. this beautiful beast is not a carbon copy of their Spa iron. That was bored out to 6.9 liters but they stick to 6.3 for customers since block walls get thin at the seven liter limit.

I gather they think the car to be hot enough for buyers at 6.3 anyway. Always reluctant to discuss power, DB admitted ''over 320 DIN'' versus 250 stock. Waxenberger got 296 from a 6.3 in Macao while guesses at Spa soared clear up to 500, "which just makes me laugh," the tall, dark engineer insists. Hints and lap times lead to a guess of something not far under 400 (467 SAE) in factory trim.

Waxenberger did admit he could easily pull another 40 from the Finnish car. When its wealthy owner lends his pet to, say, ex-Mercedes racer Aaltonen, the factory goes along and drops in a hotter works engine, too.

Even in payed-for form, the boost shows. Using standard gearing because that's all they offer, you only get some 10 extra miles per hour, or 145 in top, but acceleration glows. How about 4.3 seconds for a 0-60 (against 7 stock), or 120 mph from zero in under 14 seconds?

This is a relatively bulky 3,790 pound sedan, too, since Group II rules are strict about dieting. Mercedes shaved a bare 100 pounds plus bumpers, which everybody may re- move. Naturally DB cuts more than most there. Their quality-padded roll cage right out of a Spa car (though naturally re-upholstered for sale) puts back ounces saved in bucket seats.

About the only real removals are options like the sliding roof, air conditioning and radio. When the FIA cast skeptical eyes on sedan homologation weights for 1971, they suggested Mercedes might have to add 30 pounds at most while most current race teams will face running up to 450 pounds heavier

This car is so close to road specs that it even runs the same automatic ratios all road cousins use. Of course the four speed is tautened considerably with more laminates in the take-up plates and the car has their limited slip option. The size of the sun wheel in a planetary box limits ratio options.

Automatic upshifts now come at 5,800 rpm in drive, though racers naturally move the lever manually on a track. Shift lag is cut from half a second to 0.3, making it possible to shove the car into ''D'' out of tight bends and let the box do the work. Drivers are allowed a brief 6,000 rpm, not all that much over the stock 5,250 and fairly tame for a single overhead cam V-8

Of course virtually every engine part comes off the shelf. From bearings to pistons which are not even forged, from valves to injection pump, all parts could be duplicated at your friendly corner MB dealer. Doubled valve springs and a wilder cam are about the only internal changes. Even the cam gives only 1 mm more lift along with more overlap

Naturally, the test department which prepares such cars (reluctantly because it takes time from development) uses all usual tricks like polished manifolds, larger injection throat and head shaving. Then the oil cooler was moved out front and a race exhaust fitted

Handling is served by heavier rubber in the suspension air bags and stiffer settings for the Bilstein air oil shocks. The car I drove was actually attuned to Nurburg Ring since they didn't know where it might race.

The biggest bonus comes from 15-inch rims either 10 or 12 inches wide and mounting Dunlop racing rubber. Such foot prints alone lowered Ring lap times from 9:58 to 9:36. As a sidelight on modern tires, wide rubber fitted to their 1955 GP machine (recently unearthed from storage for a press demonstration) gave it lateral adhesion equal to a 1969 Porsche prototype. Waxenberger and crew will try anything in the name of science!

The road-roller treads and low profiles also give this 6.3 curious steering feel. A normal radial tire develops its best corner grip at 6-9 degree slip angles (nonbraced do it at 8-10) but a racing boot reches its optimum bite in the 1/2-2 degree slip angle range. This makes steering, particularly in the straight-ahead position, feel kart-quick. Actually the car had a standard ratio with a slightly smaller wheel.

Such minute adjustments are chief reason why Mercedes doesn't like to make replicas of team cars at any price. They feel any vehicle bearing that star must be totally right or not race. Even fender bulges to cover those wide tires to the maximum allowed were first faired into the rear doors to MB coachwork standards and then the whole was put in a wind tunnel to be sure boundary layer flow and car balance hadn't suffered. Fanatics, this lot!

Four-wheel disc brakes are used with DS 11 Ferodo pads such as any road racer might specify, but stopping is an Achilles heel of the brute and vented discs are only a start. Mercedes charted brake wear for each of their seven trial tracks just as they did consumption, another shortcoming of the 6.3 racer.

But they hadn't seen what Finland calls a "race track," carved out of an old gravel quarry and literally falling off one rim of same. Waxenberger merely smiled. There are always sintered pucks if somebody truly fast takes it racing. But you can fry such pads on an incautious pit stop so they don't put them on semi-pro cars.

And then we got the car underway, moving the tunnel-top lever to drive and inserting a bolt throught the housing cap to prevent sudden and inadvertent downshifts past neutral to reverse at speed. We left the poor owner behind, chewing past his fingernails to about the third joint.

It bombed right up to a 10% grade, accelerating all the way without even gulping. Going down the other side the car understeered with grim determination until I got brave enough on the narrow and tree-lined track to tweak the fast-feeling steering and to stomp the throttle. With the tail hung out artificially, that star on the hood looked more like a dollar sign.

Since the car was set up for what Waxenberger calls a fast course, like the Nurburg Ring, it naturally took to fast sweepers in Finland like you were icing a tasty cake. A good lap at Hamennilinna runs around 75 mph for the 1.8 miles, including all the tight ones, so their three fastest curves, including one entered off-camber, are right where fourth gear begins to pull - and where the Stuttgart wild one goes best.

With its vast thirst and hefty profile, this may not indeed be the ideal racing tourer but the plain panache of doing your thing that rapidly behind a polished wood Mercedes dash and with such a solid chance of survival surely makes it one of the most desireable track cars around.



material supplied by:
Star Motors