My Personal Deuce has the ether injector, once you energize it the ether will discharge when the engine starts cranking, that truck will start at 25 degrees or higher without ether the lower the temp the further i depress the pedal my 543 has a non-lighting manifold heater it will start at 25 degrees by using the heater as a fuel enrichment device. i trigger it for two seconds and then crank the engine when it really gets cold that doesn't work. At ten below I use a healthy shot of ether sprayed after the air cleaner directly into the intake, i then depress the throttle halfway and with a little luck the truck fires right up. the coldest i have ever managed to get one of these trucks to start was at 28 degrees below zero. The big problem was not getting the engine to ignite but the fear of blowing a head gasket or other damage. Anytime you start one of these engines at freezing or below i strongly advise that you keep the engine running at the lowest possible RPMs for several minutes so all the parts are happy. Regardless which starting system you have if it is in proper working order and you have a solid motor and fuel injection system your truck sould start at 20 degrees without battery warmers, block heaters, or other devices