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 Walding, the 409 guru from General Motors, operates a machine shop today with his son, Rob, outside of Atlanta in Doraville, Georgia. Over the years, Walding 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, Walding Automotive has spent a lot of time developing horsepower with late model GM LSX engines, as well. The latest 409 performance out of Walding 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 Walding Automotive would build for our car would use a 1963 409 x-block, large port cast iron heads and a stock steel 409 crank. Walding 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 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 Walding 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. Walding 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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