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Funny. You sure about that heat riser valve being eliminated in the passenger exhaust manifold after '73. I've never looked but I sure hear one flapping around on my bone stock 78 Lebaron 318 when its warming up. And all the heads had heat crossovers (LA, B, RB) that I have ever had. And every stock iron manifold I've ever took off had a heat crossover in it. My take on the electrical assist is to quicken the choke pull off so to apease the EPA goverment goons. Because like you said the quicker you get the choke off the quicker you quit spilling Polar Bear killing, ozone depleting high content carbon monoxide fumes into the air.


I guess you can never too specific here, I never meant to say that all heat riser valves went away on all applications in 73’. The OP was referring to big block application and many 73’ and later BB manifolds do not have a heat riser valve making the correct choke/heat timing more dependant on the heated spring and controller being operational. EPA mandated or not, again WHEN THESE CARS WERE NEW, all calibrations were set to include this system functioning as designed. Testing and correcting any malfunctions with the heated choke system was included in all factory published guidelines of the day as part of scheduled tune-up maintenance for these cars.


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Also I have read in FSM, a 1976 one I believe, about those electrical assist systems where they had a hot assist side and a cold assist side. Nut shell if this assist was above a certain temp it would heat up the choke faster IE already hot engine compartment or hot day. And it also had how to adjust the ohms I believe on them to regulate the speed at which they opened them. I guess it kinda sounds like your ballast deal your refering too.



Yes there is a thermal component to the correct operation of the controller; it was designed to time out quicker under heat soak conditions. The original design of the controller has factory sealed off adjustments to the bi-metal contact arm to set this temp/timing mechanically during their assembly. These adjustments were never meant to be serviced in the field however. Both the original and later button style controller were designed to be bolted under an intake manifold bolt specifically to absorb engine heat directly.

1972 Road Runner GTX 440 6bbl 5-speed
[img]http://72rrgtx.com/carpics/bucket/DSC06730r-1.jpg[/img]