Old muscle-car divorced chokes don’t work with aluminum heads lacking exhaust heat passages—but Integral electric choke conversion kits won’t fit divorced-choke carb main bodies. That’s a problem for unique setups like Chrysler’s 440 Six Pack that have no modern carb upgrade path. Westech Automotive’s solution: modding Six Pack intakes to use ’76–’79 Chrysler Holley 2-bbl remote electric choke thermostat and controller parts. Start by removing the intake for machining.
Pull off the choke rod clip at the carb.
Premodification, the choke well’s outer wall curves inward at each end. Unbolt the choke thermostat.
NAPA still sells the late choke thermostat (PN CRB 2327, left). It’s wider than the stocker (right), which is why housing-well clearancing is needed. Note how the kit’s rod comes out of the cover’s inboard (plenum) side, while the old rod points outboard, toward the valve cover.
Gain clearance by cutting away part of the choke well’s outer wall. If the mods will be done on a Bridgeport (shown), remove the carbs from the intake first—but it can be done on-car with a die-grinder or a saber-saw if the carbs are covered.
This is the outer-wall cut. Try not to break through into the intake’s heat crossover passage. The small hole is of no concern because the Edelbrock Victor heads lack heat passages. If your heads still have passages, patch any holes with epoxy.
To clear the intake flange, cut off the bottom of the new choke thermostat kit’s longer cover about 1.600 inches down from the inside of its flat mounting top.
NAPA’s kit comes fully assembled. Replace its late-style rod with the Six Pack rod. Pull the clip retaining the linkage rod to the spring.
Pry up the coil high enough to remove and replace the rod. Install the Six Pack rod so it faces the new cover’s vertical wall, exiting through its outboard slot (photo 04). Reinstall the clip.
Install the kit in the choke well, sealing the gaps between the straight cover and the curved outer wall (photo 03) with silicone.
Chrysler controlled the choke’s opening rate via a separate “control unit” (PN 4049777, discontinued). There’s no generic parts-store replacement; find one on eBay or in a wrecking yard—or see the sidebar for an alternative.
The control unit needs to see voltage in crank and run key positions. On this ’70 Road Runner, it mounts to the rear passenger-side intake bolthole.
That location gives ready access to 12-volt power. The control unit’s switch isn’t polarized and accepts ¼-inch female spades. Westech spliced a wire from one switch terminal into the large blue wire that connects the ignition circuit to the voltage regulator and input side of the ignition box’s ballast resistor. Hook the white wire from the choke cover to the other switch terminal. The circuit grounds through the cover on the intake.
The white wire feeds current to the black choke shoe’s bimetallic spring electric heater. The higher the voltage, the faster the stove heats up and the quicker the choke opens. The resistor and thermostatic switch control the amount of voltage supplied, and hence the choke’s opening rate.
Install the carbs and intake. Torque the intake bolts to 30 lb-ft using the factory pattern. Connect the linkage rod’s upper end to the center carb.
Here’s the completed installation, with the kit and control unit in place. The stock Six Pack rod hooks right up to the center carb. It doesn’t even need to be rebent. The same mod may fit other old Mopars with similar choke wells.
How it Works
Chokes overcome cold-start engine problems by supplying an extremely rich mixture. As the engine warms up, the choke is supposed to open; however, if it “sees” insufficient heat, it opens late or not at all. Usually the choke is referenced to exhaust temperature via heat passages in the exhaust manifolds, heads, and intake. If they aren’t present, an alternative must be found—like this divorced electric choke assembly.
Chrysler’s solution used a control unit with a resistor plus a normally open thermostatic switch. On a cold engine, the 10.5-ohm, 0.8-amp, resistor reduces battery voltage by increasing circuit resistance; less voltage reaches the choke coil, delaying its opening. At about 82 degrees F, the switch closes, bypassing the resistor to supply 12 volts to the choke coil and forcing it fully open. Not only is the control unit hard to find, nonstock apps may need a slower or faster opening choke. Generic resistors with varying ohm-ratings and at least 6.4-Watt-capacity could be used with no switch to vary the choke opening rate. Higher ohm ratings delay opening, lower ohms speed it up.
