The SHELBY AMERICAN
Fall 2016 7
Back in 1964 when Peter Brock
began designing the unique compo-
nents for Shelby American’s special
GT350s, he initially mounted his de-
sign for the Mustang’s now familiar
hood scoop “backwards” to improve its
performance. The problem was that a
reversed scoop looked “wrong” to the
higher-ups at Ford, so they balked at
the idea, saying it was “rather like
wearing your shoes backwards.”
Brock tried to explain that the
base of the windscreen was a high-
pressure area that would create some
forced induction at higher speeds. Un-
convinced, the suits only partially
agreed that Brock’s aerodynamic prin-
cipals might be sound (as he’d solidly
proven by the shape of his highly con-
troversial Cobra Daytona Coupe) but
his new idea for a “backwards” hood-
scoop on the Mustang still went
against all “common wisdom” and was
eventually rejected. Conventional
practice for all race cars of the era was
to face the opening of a hood scoop into
the theoretical flow of on-rushing air.
Ford didn’t use wind-tunnels to
test new designs in that era or they
might have learned that, indeed, there
was great pressure at the base of the
windscreen, and even more at the nose
of the car. On the hood’s surface, how-
ever, just a few inches back from the
grill, the disturbed air was flowing a
couple of inches above the hood’s sur-
face; not an ideal location for pressure.
The flow off the nose of the car was al-
ready being affected by the pressure
build-up being created at the base of
the windscreen! It was this invisible
bubble of pressure that Brock wanted
to tap into to improve the GT350’s per-
formance.
The concept had already been
proven on his Daytona Coupe. The
small induction inlet was almost hid-
den in the surface of the hood behind
the slight bulge that had been created
to cover the eight stacks on the Day-
tona’s Weber carburetors. In the Day-
tona’s first test at Riverside, in
February of 1964, the inlet pressure
had been so great that it had blown
out the rubber seal between the inner
hood surface and the “turkey pan”
under the carburetors! Had this phe-
nomena not been discovered in testing
and the intake system perfectly
sealed, the ever-increasing pressure at
maximum speed might well have
caused the Daytonas to run lean and
blow their engines.
This was a speed secret that Brock
wanted to use on the GT350 Mustang,
but “common wisdom” prevailed and
his hood scoop was mounted facing
forward. It was nominally effective but
performance could have been im-
proved had hard-won experience been
used to better effect.
A correct “backwards” hood scoop
has now been incorporated on one of
the two “new” Jim Marietta-built pro-
totype GT350R2s being developed by
Jim’s Original Venice Crew. Further
track tests should soon confirm the va-
lidity of the idea.
Other originally rejected (because
of cost) ideas on the new Marietta
GT350R2 Mustangs, like Ford de-
signer Klaus Arning’s Independent
Rear Suspension and an entirely new,
aerodynamically-efficient front va-
lence with flexible lower air-dam (also
by Brock) have been track-tested,
showing significantly positive results.
We almost hate to bring this up,
but Chevy started using Brock’s idea,
rejected by Ford, which they called
“cowl induction” in the late 1960s with
their Chevelles. The principle was
eventually incorporated into their Ca-
maros and Corvettes…and even pick-
trucks! Scoops may look cool but cowl
induction works!
LOOKS WRONG - WORKS RIGHT
50 YEARS OLD AND STILL ON THE CUTTING EDGE
In 1964, if anybody had told Peter Brock that fifty years later
his Daytona Coupe would still be winning races he probably
would have told them there was a better chance of a man
walking on the moon. Australian Richard Bendell’s Daytona,
designed by Ross Holder and chassis builder Michael Borland
is still competitive against current Ferraris, Porsches and
McLarens. It raced at the Sebring 12-Hours this past spring.