Dual carberator adjustment

sturgis 39

sturgis 39

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What is the best way to adjust dual carbs. The carbs are on the car and it idles at 1100 rpm. The throttle idle adjustment screw is turned away from the stop as far as it will go. The coke lever is not engaged. Is this where you hook up the vacuum gage and adjust the two idle adjustment screws and try to obtain the highest vacuum reading? Do you do one carb at a time?

Thanks
 
first you need a uni sync, a hose can be used to help even the carbs but it will never be as accurate as a uni sync, separate the carbs, no linkage from one to the other, get the car where it will idle, 1100 is to high, 400 to 500 is plenty, adjust idle mixture screws on one carb at a time till they idle smooth, then put uni sync on one carb and adjust it, the get the bubble on the other carb at the same higth as the first, keep adjusting the idle set screw on carbs til they are the same on the uni sync at around 400-500 rpm, then hook up the linkage to the carbs, as a side note, if you cant get one or both carbs to idle down check to see it the throttle plates are being held open by hitting the intake manifold under the carb
 
You do not need a unisyn. With practice the hose method can be every bit as accurate. The cam you have in the engine is going to determine what your idle speed is going to be. If you have an aftermarket cam, 400 - 500 rpm is out of the question. I like a little higher idle speed as it gets more oil and more water flowing through the engine.
 
I use a Uni-Syn on mine but I'm using 4x2's, by the time I go through them all I have forgot what the others sounded like. You do get strange whistles and noises through the hose when wearing hearing aids. I do good just to see the little red doo-dad in the Uni-Syn tube.

Vergil
 
An old "down-on-the-farm" trick that I have used for a lot of years, is to cut a 2 or 3 foot length of vacuum hose, place one end in your ear and the other end down the airhorn of the carbs, moving it from side to side while turning the mixture screws. Listen for the same percolating/hissing noise from both barrels of both carbs, and you're there. I have re-checked myself with a Uni Syn and found the farmer method to be spot on, although the Uni Syn is best used to sync the idle speed and "draw" of both carbs, not the mixture screws.
Also great for removing earwax in the event of a backfire...
 
Last edited:
uncle max said:
An old "down-on-the-farm" trick that I have used for a lot of years, is to cut a 2 or 3 foot length of vacuum hose, place one end in your ear and the other end down the airhorn of the carbs, moving it from side to side while turning the mixture screws. Listen for the same percolating/hissing noise from both barrels of both carbs, and you're there. I have re-checked myself with a Uni Syn and found the farmer method to be spot on.
Also great for removing earwax in the event of a backfire...
Click to expand...

Uncle Max.... does it cure tinnitus and trim ear hair? :D
 
Sturg,
What Jack and Uncle Max said in my humble opinion. On a 2x2 its all
you need....turn down the radio and enjoy the hiss....hell at least try it!
Charlie ny
 
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