Carb tuning question
10-07-2013, 10:29 PM
#1
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Carb tuning question Ok this question didn't get answered much in my other thread so I figured I would make a separate thread to hopefully get some more answers. So my a/f at idle are at 12.0 no matter how much I turn in the idle mixture screws until it gets to about only 3/8 of a turn out from bottomed out. Then the idle seems to be rather erratic.
So I was wondering if you guys think i should make a idle air bleed change. Or should I drill a hole in the butterfly's? Tomorrow I'm gonna get the car to idle the best I can, then see how much of my transfer slot is exposed. Help would be greatly appreciated.
So I was wondering if you guys think i should make a idle air bleed change. Or should I drill a hole in the butterfly's? Tomorrow I'm gonna get the car to idle the best I can, then see how much of my transfer slot is exposed. Help would be greatly appreciated.
10-08-2013, 06:25 AM
#3
Most of us seem to have the idle screws down around a half turn or less, seems to be a common affliction on carb'd LS motors.
If you want to change that then you need to tweak the idle feed restrictor and maybe the idle air bleeds. I copied this off another site
Making the IFR restrictor smaller will cut the fuel to the idle circuit so you can open up the mixture screws. This gives them more control and makes them less sensitive to small adjustments. The air bleeds adjust how flat the AFR stays across the band. The guy above needs to go slightly smaller on the air bleeds to keep his AFR from leaning out. He is actually pretty rich all around
I have mine working really well with the idle mixture screws at a half turn. Figure if it ain't broke why mess with it?
i found keeping the transfer slots around 20 thousands on both the primary and secondary really helps smooth things out with small off idle throttle movements. I backed off on idle timing to get the idle where I wanted without having to completely shut the butterflies.
If you want to change that then you need to tweak the idle feed restrictor and maybe the idle air bleeds. I copied this off another site
I have the idle and transition working much better. Had .040 idle jet and a .074 bleed, I was 1/2 turn out on the idle screws. Just off idle it would go fat as hell (11.3:1 AFR).
Now I'm running a .035 idle jet and a .080 bleed and it works great. Idle screws are out 1 turn, idles at 13.5, and in the transition cruising is around 13.2 and slowly leans to about 14.5....THEN it hits the mains (about 2,500 rpms),
Now I'm running a .035 idle jet and a .080 bleed and it works great. Idle screws are out 1 turn, idles at 13.5, and in the transition cruising is around 13.2 and slowly leans to about 14.5....THEN it hits the mains (about 2,500 rpms),
I have mine working really well with the idle mixture screws at a half turn. Figure if it ain't broke why mess with it?
i found keeping the transfer slots around 20 thousands on both the primary and secondary really helps smooth things out with small off idle throttle movements. I backed off on idle timing to get the idle where I wanted without having to completely shut the butterflies.
