Setting the mixture on a Holley carb.
08-27-2001, 09:09 PM
#1
Pro
Thread Starter
Setting the mixture on a Holley carb.
Another adjustment I also need to make is to the mixture on my carby. Everyone who's seen my car has commented on how it appears to be running very rich.
I read in a magazine article on Holleys that to adjust the mixture, I should screw the mixture screws in the whole way, and then back out 1 and a half turns.
I checked my current settings, and the screws are currently screwed out about 2 and a half turns. When I try it at one and a half turns the revs drop right off and the car won't idle.
Now I don't believe much that I read in magazines, so is this the correct way and level to adjust the carb. Should I make that same mixture adjustment and then adjust the idle back up to speed?
[Modified by AussieVette, 8:10 AM 8/28/2001]
I read in a magazine article on Holleys that to adjust the mixture, I should screw the mixture screws in the whole way, and then back out 1 and a half turns.
I checked my current settings, and the screws are currently screwed out about 2 and a half turns. When I try it at one and a half turns the revs drop right off and the car won't idle.
Now I don't believe much that I read in magazines, so is this the correct way and level to adjust the carb. Should I make that same mixture adjustment and then adjust the idle back up to speed?
[Modified by AussieVette, 8:10 AM 8/28/2001]
08-27-2001, 09:17 PM
#2
Safety Car
Re: Setting the mixture on a Holley carb. (AussieVette)
First lower your curb idle. Then turn the mixture screws in until just when the engine slows down(stumbles). Back the mixture screws out 1/4 turn from stumble. Re-adjust curb idle. If at all possible, make the mixture adjustments with the air filter installed.
[Modified by Jvette73, 7:18 PM 8/27/2001]
[Modified by Jvette73, 7:18 PM 8/27/2001]
08-27-2001, 09:27 PM
#3
Burning Brakes
Re: Setting the mixture on a Holley carb. (AussieVette)
The method I (and many others) use is to adjust the idle mixture circuits to achieve the highest vacuum reading. Hook a vacuum gauge to an unported vacuum outlet (i.e. intake) and adjust the primaries equally to get the highest vacuum reading then reset the idle speed (which usually rises as mixture improves). Then repeat on the secondary side. You may have to repeat the procedure a few times to get it just right but the end result works.
If you get Chevy High Performance magazine, there was an extensive tech article on how to adjust Holley carb idle mixture in the Aug 2001 issue.
One and one half turns is the commonly recommended starting place but frequently is not the optimal setting so don't get hung up on it. The only issue with number of turns is that if you have to totally close or open the mixture screws to achieve a decent idle could indicate a idle circuit problem or that your carb is jetted either too lean or rich which will require jet changes.
Mark
[Modified by mdsmith, 9:14 PM 8/27/2001]
If you get Chevy High Performance magazine, there was an extensive tech article on how to adjust Holley carb idle mixture in the Aug 2001 issue.
One and one half turns is the commonly recommended starting place but frequently is not the optimal setting so don't get hung up on it. The only issue with number of turns is that if you have to totally close or open the mixture screws to achieve a decent idle could indicate a idle circuit problem or that your carb is jetted either too lean or rich which will require jet changes.
Mark
[Modified by mdsmith, 9:14 PM 8/27/2001]
08-27-2001, 10:52 PM
#4
Racer
Re: Setting the mixture on a Holley carb. (AussieVette)
have you changed your jets recently??? #78's are a little too much in the primaries, just ask the guys that were stuck behind me in Carlisle traffic :crazy:
