Veraciousreasoning Posted October 29, 2021 Report Share Posted October 29, 2021 Hey all, As winter draws closer and closer to my area I am noticing that my 1980 720 idles really rough when cold. It also shakes pretty bad as well. I am wondering if it is a vacuum leak or something else (engine mounts?). Wondering if there is any quick things I can check to elevate the problem as I don't really wanna change my engine mounts anytime soon. Quote Link to comment
datzenmike Posted October 30, 2021 Report Share Posted October 30, 2021 To completely vaporize the fuel droplets suspended in the intake air an engine relies on engine heat. Warmed intake air from the ATC (auto temp control) that mixes air warmed by the exhaust manifold, a coolant warmed intake, hot intake valves and a hot combustion chamber and piston. This isn't available on a cold start up so a choke is employed to make the mixture richer to ensure the most evaporation possible. Also a fast idle in employed to rev the engine and speed the warm up. To start a cold engine step on the gas pedal once or twice. This sets the choke and fast idle. Does your engine start and rev to about 1,800 RPMs? Is your ATC operative? This will include an insulated pipe down from the air filter snorkel to the sheet metal skirt bolted to the hot exhaust manifold. The ATC mixes hot air warmed by the exhaust manifold, with air from in front of the rad regulating it to around 100F. This helps evaporate the gas in the air and also prevents carburetor icing. Generally , this improves cold engine running and drive-ability. Quote Link to comment
Veraciousreasoning Posted October 30, 2021 Author Report Share Posted October 30, 2021 9 hours ago, datzenmike said: To completely vaporize the fuel droplets suspended in the intake air an engine relies on engine heat. Warmed intake air from the ATC (auto temp control) that mixes air warmed by the exhaust manifold, a coolant warmed intake, hot intake valves and a hot combustion chamber and piston. This isn't available on a cold start up so a choke is employed to make the mixture richer to ensure the most evaporation possible. Also a fast idle in employed to rev the engine and speed the warm up. To start a cold engine step on the gas pedal once or twice. This sets the choke and fast idle. Does your engine start and rev to about 1,800 RPMs? Is your ATC operative? This will include an insulated pipe down from the air filter snorkel to the sheet metal skirt bolted to the hot exhaust manifold. The ATC mixes hot air warmed by the exhaust manifold, with air from in front of the rad regulating it to around 100F. This helps evaporate the gas in the air and also prevents carburetor icing. Generally , this improves cold engine running and drive-ability. I usually step on the gas pedal about 2-4 times then start it. It idles around 1,200 Rpms for a little bit. I have my normal Rpm set to idle around 800 rpm. No, its not connected. I was planning on buying one this weekend. Quote Link to comment
captain720 Posted November 3, 2021 Report Share Posted November 3, 2021 If your distributor cap is getting yucky cold weather will really make that show up Quote Link to comment
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