36èmes Grand Prix d´Endurance les 24 Heures du Mans 1968
Circuit Permanenthe de la Sarthe
Date: September 28th and 29th, 1968
Conditions: Warm, rain overnight
Track Length: 13,469 metres
Distance: 4452.880 km
Fastest Lap: Rolf Stommelen, D, Porsche 908, 3:38.1 = 222.321 km/h
Pole Position: Jo Siffert, CH, Porsche 908, 3:35.4 = 225.108 km/h
Average Speed: 185.536 km/h
Le Mans Practice
WITH the Le Mans practice periods sharing the same weekend with the BOAC 500 the attendance of cars at the 1968 Le Mans practice was poor. But what was lacking in quantity was made up in quality by the appearance of a new 3-litre eight-cylinder Porsche and the original and the new eight-cylinder Renault Alpines. Not significant as a novelty, but indicative of the possibilities, was a Ford GT40 prepared by Willment Automotive Engineering Ltd and driven by Jackie Ickx. It was confirmed at the circuit that Matra would enter a V-12 powered car and that the marques which were unable to test at Le Mans would have another opportunity during Easter weekend - a considerable concesssion as this necessitated the closing of the main Le Mans to Tours road for more than half a day.
The New Porsche 8 Cylinder
The big surprise of the weekend was that the new Porsches had eight-cylinder engines instead of the long-rumoured twelves. There were three glass-fibre-bodied cars similar in shape to the 1967 907, but these were even longer and lower. One with detachable fins was for aerodynamic testing, one was there to try out suspension modifications and the third was just for testing. Herbert Linge, Porsche's veteran high-speed tester and race driver, and Rolf Stommelen were the drivers.
The 1968 Porsche 3 Litre was even lower than its predecessor. The tiny nose air intake was for the oil-cooler - in high performance air-cooled engines, a lot of heat was dissipated through the oil...
The basis of this car was a multi-tube space frame with some non-load-bearing glass-fibre panels in the cockpit area. Suspension was of the normal Grand Prix four-link pattern at the rear in conjunction with front wishbone and coil-spring layout. Thirteen-inch centre-lock wheels were used with Dunlop tyres.
Unsprung weight was kept to a minimum by the use of beryllium discs on the outboard disc brakes. Since berylllium, besides being astronomically expensive, produces a highly toxic dust, special nonlium rubbing surfaces were applied to the discs.
The completely new engine had a bore and stroke of 84 x 66mm giving a capacity of 2,924 c.c. Whereas the previous Porsche eight had a complex system of drive-shafts to the middle of the camshafts, this 3-litre engine had a chain or gear drive of conventional type off the nose of the crankshaft. Bucket tappets - two per cylinder - were set at a 70-degree angle.
Bosch low-pressure fuel injection was used, metering being by means of an eight-cylinder piston pump which was bulky but did not require electric pressure pumps. It was driven by a cog belt off the end of the right-hand inlet camshaft. Fuel was injected into the tops of the intake trumpets about six inches above the throttle plate. There were two plugs per cylinder.
The six-speed transmission was completely new and featured an outboard three-plate Borg and Beck clutch driven by a quill shaft from a reduction gear on the engine. The quill shaft passed through the hollow first motion shaft of the two-shaft gearbox which was based round an aluminium sandwich plate acting as
a partition between front and rear magnesium gearcasings mounted aft of the final drive.
To eliminate churning losses dry sump lubrication was used. Each gear was lubricated by a jet mounted on the casing and fed from an external galllery.
Pressure was supplied and the sump is scavenged by back-to-back pumps circulating oil
from a tank mounted in front of the left-hand rear wing.
Porsche practice times were not representative because the cars were new and they were there for testing, not lap record-breaking, so the fastest lap on the Saturday was by Stommelen in 3min 45.8sec; Linge's best was 4min 13.2sec.
Alpine V8 Entry
Renaults, or rather Alpine's, V8 was entered by Alpine themselves with a second car for Ecurie Savin Calberson. Gordini's V8 unit with a ZF gearbox fitted snugly into the previous year's Alpine chassis, and Mauro Bianchi put in many trouble-free fast laps. The engine applied liberal use of titanium for reciprocating parts. The same treatment had been given to the 1,296 c.c. engines which were basically half of the V8 so far as the cylinder heads and
induction system are concerned. On the Saturday or practice Henry Grandsire was fourth fastest in 4min 25.1 sec with one of the previous year's Alpines using the new engine.
The John Willment Ford GT40
The John Willment Ford GT40 used the 4.7 litre Weslake engine and had lightweight body panels and ventilated disc brakes. Otherrwise it was as standard as most privately owned GT40s. Its best time of 3min 35.4sec raised the prospect that a GT40 would take out the event - which is exactly what happened. The introduction of the Ford chicane, which was universally regarded by the drivers as highly dangerous, not only meant that a new set of records needed to be applied, but it also put more emphasis on accelerative performance because it was located at the foot of the only incline on the circuit. That meant that large-engined cars like the Scuderia Filipinetti 7-litre Corvettes were given a slight advantage.
The Race Gets Underway
LES VINGT-Quatre Heures du Mans started at 3 pm in 1968, instead of the customary hour of 4 pm. The decision was taken in order to allow the race to adopt a pattern before darkness fell, as well as giving the drivers more daylight hours in which to settle down. However despite the earlier start time many commentators thought the Le Mans organizers should have cancelled the whole thing.
The race had to be postponed in the first place through the force majeure of the French political situation that existed in June. The difficulties of suddenly fitting this major race into an allready-crowded calendar were enormous, the race losing much of its impetus and atmosphere by being held so late in the season. Despite the organizers many changes in the rules and regulations designed, supposedly, to assist in improving the race safety, many considered that running the race in late September would find the drivers piloting their cars through dangerous overnight fog.
Treacherous Overnight Rain, But The GT40 Is All Conquering
While overnight rain made the track treacherous, it was arguably a better outcome than the potential of blinding dense fog.
Race cars of the time were still mostly based on production road cars, but by the end of the 1960s, the Ford Motor Company would enter the picture with their GT40s, taking four straight wins before the era of production-based wins would come to a close.
The Alpine Renault 3000 was only 37 inches high, and was the first serious French contendor since the Lago Talbots...