| Nissan had just seen the Prince Motor Company win Japan's
most prestigious race, the Japanese Grand Prix, using their Prince R380
race car. Nissan had done well in the race, comfortably winning in the
class they had entered, but in the race to outright victory Prince had
comprehensively beaten them.
Other Japanese cars makers had watched in envy as Prince
ran away with all the glory, not to mention the priceless publicity value
of seeing a Prince beat every other Japanese car maker, AND a Porsche 906
as well. Suddenly all the Japanese cars makers were looking to build purpose-built
racing prototypes. Hino were hard at work developing their Hino Contessa
GT prototype, which was a rear engined coupe with a fibreglass body. It's
mechanicals were based on the production Contessa coupe, but after seeing
Prince develop a twin cam cylinder head for their racer they decided to
do the same, and came up with a twin cam head for the Contessa engine.
Over at Daihatsu they were working on their Daihatsu P3 prototype, which
wa an odd looking contraption that was based in the chassis of the Compagno.
It too had a specially designed twin cam head to sit on it's 1300cc block.
It went quite well and came first in it's class in the 1966 Japanese Grand
Prix and an impressive seventh outright. Toyota were about to get serious
about racing as well, and they were preparing a race version of the Toyota
2000GT, which was actually designed and built for them by Yamaha.
With all this activity going in in the opposition camps it was no wonder
that Nissan decided that they too needed a racing prototype. Like the others,
Nissan knew little about building a racing prototype. Prince had acknowledged
their own lack of experience in racing chassis design and instead decided
to purchase a Brabham BT8 chassis on which to base their car, which was
hugely successful for them. Nissan instead decided to stick with what they
knew and instead based their car, which was to be known as the Nissan A680X,
on the chassis of the Datsun Fairlady sports car. The Fairlady had a great
chassis with excellent torsional strength, though in reality it was no
match for a Brabham space frame chassis.
Much of the design work was carried out by a Nissan engineer
called Noguchi Takashi. When designing the body he called on the help of
a Nissan designer called Kazuo Kimura, who had come up with the concept
for the Nissan Silvia, and had helped design the car. Aerodynamic testing
was pretty primative back then and there were no wind tunnels. Takashi
and Kimura instead used hydraulic testing, which sounds impressive but
actually only involved pushing scale models through the water to gauge
resistance. The end result ended up looking like one of those Alpha kit
cars that you add to a Datsun 240Z to make it look like a Ferrari 250GTO.
The body of the A680X would be constructed entirely of fibreglass.
Meanwhile, outside help had been called upon for the engine,
and the engine was going to be something quite radical. Yamaha in the 1960s,
and even still today, do a lot of engineering consultance work for other
companies. Nissan had used their services in the past, with Yamaha doing
anything from little jobs like designing the soft top frame for the Datsun
Fairlady right up to complex things like building the Nissan Silvia prototype.
At the time Yamaha were hard at work designing a new overhead cam six cylinder
engine for Nissan, which would be used in the next generation Nissan Cedric.
The engine they were working on would be known as the L20, and later versions
of this engine would power most of Nissan's range for the next two decades.
Nissan asked Yamaha to develop a twin cam cylinder head that could be adapted
to the L20 engine for their race car, and the resulting engine was called
the Nissan B680X.
The B680X engine was a 1998cc double overhead cam, four valve per cylinder
engine with three 42DCOE Weber carburettors, two spark plugs per cylinder
and two distributors. The engine produced an impressive 190hp at 6400rpm,
though was still short of the 200hp the Prince R380 had. Details about
the twin distributor set-up are sketchy, but from what I understand it
was some sort of attempt at a crude variable timing design.
The car was ready for testing by early 1966. At the Fuji
Speedway the car clocked the full 6km version of the circuit in two minutes
and eight seconds. The promising thing was that this was a full two seconds
faster than Toyota had managed to achieve with their new 2000GT, the bad
news was that this was still three seconds off the pace of the Prince R380.
Nissan continued to develop the car until it was announced that the Nissan
Motor Company and their rivals at the Prince Motor Company were going to
merge. It made no sense to continue developing a car that was clearly slower
than the Prince R380, especially when the Prince name was about to be dropped
and the R380 was soon to be wearing Nissan badges.
Nissan still found themselves with a rather potent engine
that was sitting in a Fairlady chassis. Rather than let this go to waste
the engine was fitted to a Fairlady race car that was to be known as the
Fairlady S. This car only raced once and was never seen again.
Length - unknown
Width - unknown
Height - unknown
Wheelbase - 2280mm
Weight - unknown
Top speed - unknown
Transmission - unknown
Model - B680X
DOHC 6 Cylinder
Capacity - 1998cc
Bore & Stroke - 78x69.7mm
Power - 190hp@6400rpm
Torque - unknown
Compression - unknown
Carburettors - triple 42DCOE
Final Drive - unknown