[Riles]

I need to know what to set my air to gas ratio to on my Quadra jet 650 CFM carb..

Like i should tighten them all the way then turn them ???? how do i know when to stop loosening them? Should the car be running? when i am doing this.. I am really at a loss of information herE? help plz!

1966 malibu
327 c.i.
chevelle


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Riles

 

[Rick Loncosky]

Riles, you should screw the air/fuel scews in the whole way "GENTLEY" and back them out 1 3/4 turns. This is a good starting point. With the car warm at idle, hook up a vacumn gage to the carb and adjust them to get the highest idle. you might have to go back and foreth a few times. This is my way.
This should do ya. Good Luck & Happy motoring

 

[Clark]

I just want to add something to Ricks post.

Once you have the idle mixture set for Highest idle speed, check your exhaust and see if it smells like raw fuel. Many times setting the mixture for the highest idle speed can cause the mixture to be a little to rich. If it seems rich, turn the screws in a little and check the exhaust again. you may have to find a happy compromise between speed and smell

.

Dont do the smell check until the engine is at operating temp.

I'll be getting high on exhaust, see ya

Clark

 

[Tom Mobley]

Since you've got a Q-Jet, I'd suggest starting at 3 turns out from seat, Q-Jets typically use a little more that Holley's.

Tom

 

[ricwei]

Riles: When you adjust the idle mixture screws on a typical carb you are not changing the "air to gas" ratio. You are changing the idling mixture only. This will have a slight affect on the overall air/fuel ratio, but not much.
You should get a very smooth idle as you move the screws inward a little at a time, doing one then the other. When you turn them too much the engine will slow down, start shaking, and then die. This is NORMAL. If you screw the adjusters in all the way and the engine still runs,then you are sucking air into the motor from somewhere other than the idling system.
This is undesirable because it really messes up the air/fuel ratio you are trying to achieve. We call that a vacuum leak and it is to be strongly avoided.
Quadrajets are precision carbs and will give superior results compared to most other carbs.