Idle mixture-gas milage

[luigi164]

I've read many threads about adjusting carbs, timing etc etc..
Now I have a question about adjusting the idle mixture. I know the further the screws are out the richer, further in is leaner.
Now, does this adjustment also effects the overall gas-milage ?

Luigi

 

[Toolmanmike]

Not really unless you spend most of your time idling.

 

[413]

It will use more gas idling. It will not change a thing going down the street.

 

[luigi164]

It will use more gas idling. It will not change a thing going down the street.

Oké, that's what I wanted to know. My Newport is smelling bad at idle and the fumes are killing my throat (behind the car, nót inside ) so mayby it's to rich...
Now, sometimes you read that an engine is running to lean or to rich while going down the street. How can you adjust that ?

 

[413]

Fix any Vacuum leaks, change jets, change timing.

 

[luigi164]

Fix any Vacuum leaks, change jets, change timing.

Clear ! Thanks..

 

[Turboomni]

 

[Turboomni]

 

[CBODY67]

If the fumes are THAT bad, I would suspect there should be some visible black smoke from the exhaust pipe. Unless the car has a catalytic converter and you're smelling "rotten eggs".

Also, if the fumes are that bad, do you smell hydrocarbons in the motor oil on the engine dipstick? IF you do, discover what is not right and then do an engine oil change . . . to have real oil rather than fuel-diluted motor oil in the engine.

Just some thoughts,
CBODY67

 

[thrashingcows]

I always tune my carb with a vacuum gauge...always trying to get the most vacuum. Start with the base timing and carb setting, then adjust one thing looking for higher vacuum, tweak another to compensate and continue...eventually you will get the settings right where the motor wants them for max vacuum, and every motor is different.

 

[odcics2]

I've read many threads about adjusting carbs, timing etc etc..
Now I have a question about adjusting the idle mixture. I know the further the screws are out the richer, further in is leaner.
Now, does this adjustment also effects the overall gas-milage ?

Luigi

The idle mix screws directly effect the transfer slots, which transitions to the main metering system. You want the idle screws to be set for best lean idle.

Depending on road speed, your car can be using the transfer slots and not the main jets.
This all depends on tire size, gearing, weight of the car, your 'foot' weight, engine rpm, etc.
Think about 40-45 mph as probably the upper limit for any transfer slot use.
Freeway speeds would be all main jets.

You can look into a carb and see the slots. Move the throttle blades to see how far they can open before they are not being used.