Hidden Treasure

This rare 1970 911 S/T Lightweight was hiding under a fiberglass 935 body kit.

Photo: Hidden Treasure 1
December 8, 2016

“It was a very lucky find for us,” declares Jacques Rivard; after all, stumbling upon a 46-year-old 911 S/T Lightweight doesn’t happen very often. Rivard, who completed the car’s restoration just in time for the 2016 Porsche Parade, tells us the car had been converted into a slant-nose street driver by a previous owner, who probably had no idea that the car was much more than an ordinary 911.

Digging In

In 2013, Rivard, who operates a Porsche racing and restoration shop near Quebec City, Quebec, Canada, about 260 miles northeast of Montreal, spotted a 1970 Porsche coupe offered for sale at a local insurance auction. The VIN, 9110301383, identified it as a 911S, and it was described as having been struck in the left-rear corner, leaving some damage to the rear bumper, rear body panel, and exhaust system, all issues that would be quite easy to remedy. It had also been fitted with an aftermarket body conversion kit and the original engine was missing.

Photo: Hidden Treasure 2

Intrigued, Rivard went online to bid for the car and soon became its new owner. As soon as the car arrived at his shop, Rivard and his son tried to look past the red EVEX 935-style flat-nose fiberglass body to see what lay underneath. There were a lot of interior trim bits that weren’t original; a later-model steering wheel had been installed, and a strip of cheap black felt had been glued to the front of the instrument panel. The odometer read a shade less than 68,000 kilometers (42,253 miles). Rivard had no way of knowing whether the odo was on its first or second rotation.

Crawling inside, his son noticed a driver’s “dead-pedal” that appeared to be a period-correct Porsche racing item. The two continued to poke and prod. “I was already excited; (the pedal) was (from the) factory,” recalls Rivard. “Having restored a few factory race cars I was aware that it was probably only one of more special features,” he says, “so I started looking, and under the non-factory carpet I found roll-bar mounting plates, seat belt anchors, welded heater tube outlets, and a missing ashtray mounting bracket.”

The seat track shelves in the interior were missing. In the engine compartment were reinforced shock towers and underneath there was no rust proofing.

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“The car never had any undercoating, and the lack of heater tubes in the door sills is not something that anybody will do after the build,” says Rivard. The thin steel tubes that normally house the release cables for both the front lid and engine cover were missing. The cover for the “smuggler’s box” in the front trunk floor—which houses a gas heater—was aluminum rather than steel. He’d never seen one like that before.

After stripping the paint from the roof and pulling the cheap replacement headliner (they found remnants of the original underneath), he took a micrometer to the roof panel and found it thinner than that of a standard 911. The doors still had the original internal mounting points for the pull-straps and handles. Clearly, this was not an ordinary production 911S.

Suspecting that he’d found a real factory lightweight, Rivard sent off to Porsche for a Certificate of Authenticity, which unfortunately didn’t shed much light on the matter. That document stated that 301383 was a standard 1970 911S which left the factory wearing Silver Metallic paint over Black leatherette and was equipped with tinted glass, a power radio antenna and speaker, a pair of Recaro sport seats, and a 40-percent limited-slip differential. There was no mention of it being a lightweight of any sort.

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Rivard already knew better; a detailed inspection of the tub was providing a growing list of non-standard features. Could he obtain the factory’s original Kardex build sheet? Well, yes, sort of. Through early 911 authority Prescott Kelly, Rivard contacted Dieter Landenberger at the Porsche Archives, who told Rivard that while the actual Kardex could not be found, he was able to locate data in the factory’s production book that provided additional information.

It was determined that the car had been delivered in April 1970 to Hahn Porsche in Stuttgart, close to the factory. There was nothing mentioned of the car’s first owner. If this was indeed a special car or part of a group of special cars, the next question was how many of this type had been built? Some items could be easily installed or removed, but Rivard was certain that the thinner-than-standard roof and other parts of the tub could only have been welded in on the assembly line.

Rivard then took to the internet, sharing his discovery on the Early 911S Registry’s Member Forum, hoping that the Registry’s knowledgeable members could impart more information. Data began to trickle in. It was starting to look as if Rivard had come into possession of a real 1970 911 ST lightweight.

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So, What’s an ST?

For the 1970 racing season, the Federation Internationale de l’Automobile (FIA) had allowed some important changes to production-based sports cars and GTs. These included a widened front and rear track, and Porsche’s competition manager, Rico Steinemann, promptly filed paperwork for the new C-series 2.2 911S as a Group 4 Special GT car. The new competition 911 would be referred to internally as the “ST.”

The goal was to produce the lightest possible 911s for rallying and racing, and the first step was trimming as much weight as possible from a stock 911S coupe to establish a starting point for FIA Homologation. Then, the car could be further lightened. To achieve the target curb weight of 840 kg (1,848 lbs) that would be legal for a “base” 911S coupe, the factory created “Option M470 (Delete).”

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All 911Ss were fully equipped with top-of-the-line trim and comfort items; in other words, they all had Option M470; deleting that “Option” simply meant that the car was built without any of those items, which brought the dry weight down to just over 2,040 pounds. That was accepted by the FIA as the legal weight of a base 911S. From that new, lower starting point, Porsche’s Competition Department could then remove even more avoirdupois for a class-legal weigh-in.

Lighter materials were used wherever practical. Rivard says “about 40 special sets of thinner-gauge (0.70 mm) sheet metal were produced for the factory race and rally cars.” In his book “Excellence Was Expected,” Karl Ludvigsen places that number at about 30. The special thin sheet metal, exclusive to the works-built cars, was employed for the seat pan rear and side panels and rear inside panels, the roof and quarters of the works-built cars. The factory, says Ludvigsen, also produced about 100 packages of additional lightweight parts and made them available to privateers.

Standard steel bumpers were replaced with aluminum alloy, there were no bumper guards, and the steel engine lid was replaced with aluminum. Along with that thinner-gauge steel for the roof and inner structure, the factory racers were fitted with doors made of an aluminum alloy made rigid by light-gauge (0.75 mm) steel framing. The polished aluminum horizontal grille bars on the engine cover were tossed in favor of an even lighter mesh screen, and the engine lid name and model badges, by themselves just a few grams each, gave way to a paper-thin decal.

Photo: Hidden Treasure 7

The stock steel front and rear fenders were widened with softly-rounded flares to accommodate wider wheels and larger tires. Because Fuchs did not offer an 8.0-inch-wide wheel with the desired offset at that time, many STs were fitted with Minilite alloy wheels in the rear and are often seen with them today. Fiberglass was used for the front and rear fascias, and a plastic front lid was offered as an option. Rubber hold-downs saved a bit of weight over the stock 911 latch assemblies, and thus the factory omitted both the wire release cables and T-handles and the thin steel tubes that housed them.

All window openings except for the windshield were fitted with Plexiglas and the interior was stripped. Thinner Glaverbel laminated glass was available as a windshield replacement. There was no carpeting, glovebox door, passenger-side sun visor, joint sealing or undercoat. The ashtray assembly was removed, as were those welded-in tubes for the hood release cables, seat-slide supports on the central backbone, the standard seat belt anchor points, heat duct tubes, front and rear cover locks, fog-lamp recess covers, front torsion covers and the caps over the rear torsion bar ends, even the dust-caps on the Fuchs wheels.

A few important items were added, in particular, a transverse brace between the front strut towers, and in some cases, a carefully-fitted roll-over bar. For rallying and racing, either an 80 liter (21.1 gallon) or 110-liter (29.0 gallon) plastic fuel tank with through-the-lid filling capability, along with a space-saver spare tire were fitted. The result was a car that was nearly as light as the 911R. Lightest of all the STs, and indeed the lightest 911 ever constructed, was the one special car prepped for the 1970 Tour de France Automobile sports car race. That car was shaved to just 1,720 lbs, or 789 kg, by employing a number of titanium and magnesium parts.

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Along with the body mods and extreme weight loss, these special cars enjoyed numerous mechanical changes from stock. Since the 2.2-liter cars would be at some disadvantage in the up-to-2.5-liter class, the STs needed larger engines. The FIA allowed oversized bores, but the 2.2’s stock stroke of 66 mm had to be maintained. New Biral cylinders (cast-iron with alloy cooling fins) one millimeter larger in bore diameter (87.5), or the same size as those used on the 908 race car’s engine, brought displacement up to 2,247cc. This would become known as the “2.3.”

Close attention was paid to the engine’s internals, with polished connecting rods, 906-spec camshafts, and careful balancing. With 10.3:1 compression, twin-plug ignition, and Bosch high-butterfly mechanical fuel injection with a twin-row, six-plunger pump, the 2.3 Type 911/20 engine produced a hefty 250 hp at 7,800 rpm, along with 188 lb-ft of torque at 6,200 rpm. In 1971, the engine was enlarged to 2,381cc, producing 260 hp.

A 2.5-liter racing engine—based on the 2.4 from 1972—appeared next, taking further advantage of the class displacement limit. This Type 911/70 measured 86.7 × 70.4 mm for a displacement of 2,492cc, and was quite muscular, producing 270 hp at 8,000 rpm and 191.6 lb-ft of torque at 5,300 rpm. Flywheel issues reported with that engine prompted a redesign, which reverted to the earlier and more reliable 66 mm stroke but an enlarged 89 mm bore.

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Accurate production data for these special lightweight cars is difficult to pin down; various sources offer a range of numbers of between 35 and 44, not including the 1970 Tour de France car. Landenberger says the factory’s production records show just 41 911STs built to this specification between September 1969 and July 1970.

The late Patrick Paternie’s “911 Red Book” states that 35 STs were built between 1969 and 1971, plus that one super-light example for the 1970 Tour de France. Paternie lists seven 911STs specially numbered for rally purposes in 1970: 9110300001, 002, and 003, plus 300102, 949, 950, and 1127. Writer John Starkey says there was a total of 36, while another source says there were just 18. Paternie says the first three cars in this group of STs, numbers 300001, 002, and 003, were fitted with Type 911/22 2.2-liter engines. 2.3-liter racing engines (Type 911/20) were fitted to numbers 102, 949, and 950.

There may also have been some others, says Swiss researcher and ST owner Marco Marinello. He has compiled a list of 44 chassis numbers from 1970 for what are called the 930 kg (Rally weight) cars. “When I look at the 44 1970 cars and look at the known VIN numbers of 2.3 race cars, I think about 15 to 20 were 2.3 race cars and about 20 to 25 were lightweights,” says Marinello. “In 1971, I count 20 lightweights in total and eight had the 2.3 engine, Option M491. The 2.3 was much more a race car then the 1972-only 2.5, which was mostly a 2.4 steel shell.”

Photo: Hidden Treasure 10

Of those 44 examples from 1970, he says, perhaps a third would be prepared for rally duties, another batch was built for circuit-racing. Those had widened front fenders and quarter panels, while the remainder, perhaps no more than eight to 10 units, retained their original “narrow” bodies and stock fuel tanks, and were intended for factory executives or special customers.

Making it Right

Rivard’s car, 9110301383, is among the latter, and per its CoA, was trimmed with a few of the items the M470 Delete option would have removed. Marinello views these as a “gentleman club sports-racer 911S.” He tells us that “most were raced or rallied but a few were sold or used by the factory.” Says Rivard, “With what I know now it probably was built for a special customer, mainly for street use.”

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It closely resembles a narrow-bodied lightweight car illustrated in an early sales brochure for the new C-series 2.2-liter 911. The brochure includes several photos of what became known as the ST, along with a table of Technical Data in which is shown two versions of the 911S with different weights.

One photo shows the interior of a red car with deep rally bucket seats and simple door cards with pull straps, which might be the first time this type of door panel was used. They became standard fare on the later RS 2.7 Carreras. Rivard tells us he found one of those rare brochures tucked into a used 1970 911E that he purchased back in 1974. He’s happy that he didn’t just toss it away. “I keep everything!” he says.

In late 2013, Rivard embarked on an intensive effort to restore 301383 to its original delivery specifications. The body shell was taken down to bare metal, which revealed rust in the floor pan, suspension pan, rockers, and a few other areas; “Not too bad for a car that came without any rust-proofing,” he says. The front latch panel needed replacement; a later one had been installed to accommodate the EVEX nose.

Proper repairs were made, using many OEM factory parts including new rear quarter panels. The car retains its original aluminum engine cover and rear body license panel. It was then resprayed in its original Silbermetalic hue. Inside, we see that it is fitted with correct thin carpeting and headliner, its original as-delivered sport seats and no rear seats. The door cards, as noted above, were recovered in minimalist RS-style.

Rivard says he doubts that the car’s original engine made it to Canada; fortunately, the shop had a correct 911/02 case on the shelf, along with most of a correct Bosch MFI system, so the car now has a proper fuel-injected 2.2-liter six. The car’s original five-speed 901 gearbox with its limited-slip differential was overhauled, along with the rest of the car’s mechanical components. The correctly-dated deep 6.0-inch wide Fuchs alloy wheels were refinished.

“We doubt that our car ever raced professionally,” says Rivard, “but it was intended to do so when it was built, for sure! I can tell without any hesitation that all (the changes were) factory, everything is well documented. If somebody else had built it, it would not be in the Porsche production book. The silver color is unusual for rally-spec cars, (as are the) Recaros left and right instead of standard race buckets, tinted glass, and the power radio antenna. These make the car very special as a precursor of the RS lightweight.” Scaling 120 kg less than a 1973 Carrera 2.7 RS Lightweight, the STs were all quite rare and special cars.

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  • 30 Years of Excellence
  • Market Update: Boxster & Cayman
  • We drive two tuned 1972 911s
  • Racer Jon Milledge
  • Snodgrass 997 Turbo coupe
  • The Nearly Pristine 914
  • When TAG-Porsche & McLaren Split
  • 2017 TechArt 911 Carrera S
  • 1987 vs. 2017 911 Tech
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