1979 Truck 20R carb tuning help?
#1
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Location: Columbia County, GA
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1979 Truck 20R carb tuning help?
I have looked but cannot find the factory specs for the idle air mixture screw, I know it is running rich, but how much I do not know. It was 5 turns out from closed.
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Truck is tuned up. new plugs, wires, cap rotor, air filter fuel filter... everything that I can think of that can affect tuning... I was getting around 15mpg, now about 12mpg. Driving is 60 highway/40city, driven aggressively for the little truck. Nothing rebuilt... any specs? I cannot find them anywhere.
#6
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Usually, turn the idle mixture screw in until it just bottoms out, the unscrew about 2 1/2 to 3 1/2 turns. Start engine and set the idle speed to around 750-800 rpm. Adjust the mixture screw in/out 1/2 turn to get smooth idle. I usually bump the throttle after each adjustment checking for smooth acceleration off idle.
You can download the FSM here http://www.ncttora.com/fsm/ Scroll down to the 79-85 section. There's a lot of info in this PDF file. Carb adjust is in the fuel section
You can download the FSM here http://www.ncttora.com/fsm/ Scroll down to the 79-85 section. There's a lot of info in this PDF file. Carb adjust is in the fuel section
Last edited by Lons81; 02-10-2012 at 06:22 AM.
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Would this be a stock carb or a weber carb or asia carb?
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5 turns out sounds extremly rich, any mods? i expect your plugs were looking black, most carbs, you will bottom out the air mixture screw(s) then start at 1 1/2 turns out, if doing by ear, i would do what was mentioned above by lons81. jmo
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