When a customer with an ultra rare 1961
Chevrolet 4-Door Hardtop Impala wanted
to bring his car to another level of
performance, he called on the
restoration team at Select Motors.
The period correct move that
would make the car most desirable and
have the appearance of being built in
the 1960's was to install a dual quad
409.
The installation had to be very
functional and needed to look like it
possibly was put together at the
factory.
Who better to prepare a dual quad 409
for this car than one of the original
mechanical
engineers who developed the dual quad
409 in the 1960's?
Lamar Walden, the 409 guru from
General Motors, operates a machine shop
today with his son, Rob, outside of
Atlanta in Doraville, Georgia.
Over the years, Walden
Automotive has built an incredible line
of performance parts for the 409 engine.
High performance aluminum
cylinder heads, aluminum water pumps,
high performance rotating assemblies and
valve train components.
Additionally, Walden Automotive
has spent a lot of time developing
horsepower with late model GM LSX
engines, as well.
The latest 409 performance out of
Walden Automotive is an all aluminum
509 cubic inch engine, which can be
stroked considerably larger and is
mostly compatible with 409 designs and
utilizes a Big Block Chevy rotating
assembly and main bearing design.
This block will soon be mass
produced by World Products and will be
featured in an upcoming issue of Super
Chevy Magazine.
Back
to our car.
We wanted an original look.
The engine Walden Automotive
would build for our car would use a 1963
409 x-block, large port cast iron heads
and a stock steel 409 crank.
Walden custom forged pistons
suitable for pump gas, H-beam rods and a
roller cam valve train would all be
stealth upgrades that wouldn't take from
our original appearance and would make
our 409 car a serious performer.
A set of 1963 409 dual quad Carter
four-barrel carburetors were acquired
from a
vintage
carburetor restorer and would sit on top
of an original GM dual quad intake
manifold.
We purchased a reproduction dual
quad air cleaner, fuel lines, linkage
and reproduction cast iron manifold
headers that were used on factory high
performance dual quad 409's.
All of these products were
purchased from Show Cars Automotive Inc., a
manufacturer of classic Impala parts
that specialize in 409 reproduction
parts.
Alumitech Reproductions produces
aluminum performance reproductions of GM
radiators with stamped tanks as opposed
to fabricated radiator tanks
usually
used on aluminum radiators.
Our radiator will be painted
satin black to keep our car's 1960's
look.
However, we did opt to have our
upper radiator hose connection moved to
the driver's side of the radiator for
better cooling.
Other
upgrades and modifications performed to
get the Impala ready for a high
performance 409 include a built turbo
400 3-speed automatic; which utilizes an
electric kick down switch on the
accelerator pedal as opposed to adding a
kick down cable used on a turbo 350.
Shift Works, a company that specializes
in transmission transplants, produced a
shift lens indicator for the turbo 400
3-speed that would take the place of the
original power glide indicator.
Precision
Industries provided us with a 10" torque
converter with a 2400 stall.
Precision Industries is a leader
in torque converter production and
torque converters which produce stall
torque ratios considerably higher than
stock converters.
Stall torque ratio is the amount
of torque multiplication that takes
place before a converter locks up.
A typical stock converter might
multiply torque 1.9 to 2.0 before
lockup.
Precision Industries converters
typically make STR's of 2.55 and on a
more expensive custom converter more.
Precision Industries is one of
the few torque converter companies that
has torque converter dynos that can read
STR; this often makes STR numbers the
subject of incorrect or overstated
numbers by rebuilders.
Although
Flowmaster did not have an exhaust
system package specifically for a
four-door 1961 Impala, the guys at
Flowmaster were able to put together an
exhaust to the axles kit and a tailpipe
kit for a two-door Impala to work for
us.
We opted for 70 series Flowmaster
3-chamber mufflers for a quieter mellow
Exhaust tone.
Our
ignition system used on the dyno at
Walden Automotive was a MSD stand alone
distributor with an electronic module or
HEI distributor and an MSD Blaster Coil.
We expect this to be an excellent
upgrade over points ignition.
If the car looks like it's going
to have any cold start issues, we may
later include a MSD 6AL Amplifier.
The battery that we choose to kick off
all of the fun is an Enersyn Odyssey
fiberglass matt battery.
Enersyn builds a battery with
virgin lead plates.
The virgin lead is more pure and
can be made into thinner plates with
fewer cavities.
Because these plates can
effectively be made thinner, more plates
can be installed in one battery case.
Fiberglass matt is used to
insulate these plates.
The outcome is a much heavier
battery but an incredibly stronger and
longer lasting battery at a reasonably
but higher price than traditional
batteries.
The charging system on early 409 cars
used a generator.
Powermaster builds an alternator
that closely resembles a Chevrolet Delco
generator.
This alternator in disguise, or
the Powergen as Powermaster calls it,
produces 75 amps peak power.
Walden Automotive shipped our
engine with a block mounted mini
starter; an a-typical application in
that most 409's are cranked from a
bellhousing mounted starter.
The
Hotkis style rearend in our 1961 Impala
had 3.36 gears and an open differential.
The gears were an acceptable
ratio so we reused the original gears
and installed an Eaton Carbon fiber
clutch positive traction unit from
Randy's Ring & Pinion.
The Eaton unit was considerably
larger and stronger and required
clearance work with a grinder to fit in
the 55P housing.
After some drive time on our 409
Impala, we may consider rear suspension
upgrades offered by Global West.
This 1961 Impala four-door
hardtop is a very fine super sleeper
409.
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