Carb question.

[Roadcuda]

I hope you guys don't mind if I ask a question about the Carter 3854 carb with the Commando 273 my '65 Barracuda. I have some idea on how the idle mixture screws work, controlling the amount of air that's mixed with the gas, and how to adjust it. If I'm correct these screws affects the amount of gas that the carb lets through and which I believe affects how much gas the car uses. But I haven't found in any of my books, including the Carter Carburetors book, on what the By-pass idle air adjustment screw does and what to look for when adjusting it. Do I have to adjust it along with the mixture screws, separately, or not at all? it's the large copper screw between the mixture screws. I ask this question because so far I'm only getting about 12 mpg in this car,( using a light foot,) while my '64 with same setup can get 15, or better sometimes. I know, these cars weren't built for gas mileage, and we are all aware of what gas is going these days, so I'd like like to get the best I can out of them. Thanks.

 

[moparchris]

I know that the center screw is used to adjust idle speed by letting in more air, same as opening the throttle more, which then the idle mixture is adjusted accordingly. I think there are many factors that influence mileage. Things like timing, health of the motor,transmission type and amount of slippage if its auto, what gear ratio, what parts are in the motor (I.E. hipo versus lopo) and lastly how the carb is set up. Assuming all the other factors are the same I would look at the jetting/ metering rod sizes and lean it out and see if that affects mileage.

 

[69hemibeep]

I know that the center screw is used to adjust idle speed by letting in more air, same as opening the throttle more, which then the idle mixture is adjusted accordingly. I think there are many factors that influence mileage. Things like timing, health of the motor,transmission type and amount of slippage if its auto, what gear ratio, what parts are in the motor (I.E. hipo versus lopo) and lastly how the carb is set up. Assuming all the other factors are the same I would look at the jetting/ metering rod sizes and lean it out and see if that affects mileage.

That was a pretty long "I don't know" :acme: :lmao:

 

[Roadcuda]

I know that the center screw is used to adjust idle speed by letting in more air, same as opening the throttle more, which then the idle mixture is adjusted accordingly. I think there are many factors that influence mileage. Things like timing, health of the motor,transmission type and amount of slippage if its auto, what gear ratio, what parts are in the motor (I.E. hipo versus lopo) and lastly how the carb is set up. Assuming all the other factors are the same I would look at the jetting/ metering rod sizes and lean it out and see if that affects mileage.

That was a pretty long "I don't know" :acme: :lmao:

Oh, that's great help. And I thought I could count on you guys!!!! :acme: :jester: :lmao:

But, as to Chris' points, according to the receipts I have the hipo engine has about 5k on it since it was rebuilt, tranny doesn't slip, 2:76 gear, and the carb was set to factory specs.

 

[moparchris]

I know that the center screw is used to adjust idle speed by letting in more air, same as opening the throttle more, which then the idle mixture is adjusted accordingly. I think there are many factors that influence mileage. Things like timing, health of the motor,transmission type and amount of slippage if its auto, what gear ratio, what parts are in the motor (I.E. hipo versus lopo) and lastly how the carb is set up. Assuming all the other factors are the same I would look at the jetting/ metering rod sizes and lean it out and see if that affects mileage.

That was a pretty long "I don't know" :acme: :lmao:

I know right?! I guess my run on sentences aren't the only thing I "specialize" in.

 

[Basketcase]

yeah... I do mind...can you delete your post? :acme: :jester:

 

[moparchris]

Now Dave dont be mean. I think Dave has been drinking the blue stuff again!