Edelbrock Carb Tune
- Thread starter Tfitch03
- Start date
Screaming Metal
Active Member
Ya have to be careful and take your time, thats what your doing and you will learn alot that way. Since you changed a couple of things, and when you went to the bigger jets....that should tell you that your richness happening on the mains was too rich for the rpm and/or vaccum being pulled.
When you adjust a carb, think of it as Mike said. Its dumber than a box of rocks. It richens at this vaccum, overlaps here there and yonder. A bone stock carb is made to do a certain thing at certain rpms and engine loads.
1st and foremost, for the street, it has to idle. You have no trouble there.
Off idle to the main transition, thats where your lean spot comes in. You might be what we call 'Under the Curve' in the racing community. You want a shot of richness just as your butterflys dump. If you move the metering rods too early, your gonna have a rich bog if you go to fat. Your probably close to optimum on your jets. If you don't have enough adjustability in your metering rods to barely richen it up, ( I used to get a drill, blue up the metering rods, get some emery paper, spin the rod and sand it down to get what I wanted, then used a optical comparator to get both of them the same.), if you get it to where the stumble is ever so slight at just above idle, you can raise your float level just a hair, then tune it back with the idle mix screws.
Don't rule out tightening up on your accelerator pump linkage, to where it has very little slack. To the point of a shot being delivered just as you barely move it. If your dribbling from the squirters, your pushing down on the accel. pump too much, just back off a little on the linkage. You want to look at it and have it squirt....
Sometimes, the best thing is to just richen it up at idle a hair to eliminate it, if adjusting is too bothersome.
Just take your time and go slowly....don't get frustrated....
When you adjust a carb, think of it as Mike said. Its dumber than a box of rocks. It richens at this vaccum, overlaps here there and yonder. A bone stock carb is made to do a certain thing at certain rpms and engine loads.
1st and foremost, for the street, it has to idle. You have no trouble there.
Off idle to the main transition, thats where your lean spot comes in. You might be what we call 'Under the Curve' in the racing community. You want a shot of richness just as your butterflys dump. If you move the metering rods too early, your gonna have a rich bog if you go to fat. Your probably close to optimum on your jets. If you don't have enough adjustability in your metering rods to barely richen it up, ( I used to get a drill, blue up the metering rods, get some emery paper, spin the rod and sand it down to get what I wanted, then used a optical comparator to get both of them the same.), if you get it to where the stumble is ever so slight at just above idle, you can raise your float level just a hair, then tune it back with the idle mix screws.
Don't rule out tightening up on your accelerator pump linkage, to where it has very little slack. To the point of a shot being delivered just as you barely move it. If your dribbling from the squirters, your pushing down on the accel. pump too much, just back off a little on the linkage. You want to look at it and have it squirt....
Sometimes, the best thing is to just richen it up at idle a hair to eliminate it, if adjusting is too bothersome.
Just take your time and go slowly....don't get frustrated....
Screaming Metal
Active Member
When you get it really, really close, you can probably get it out with your timing.....
I'd try the timing first, as Mike said, sometimes those motors will fool ya....
I'd try the timing first, as Mike said, sometimes those motors will fool ya....
Mike
Well-Known Member
With the reminder you don't want to rattle the rings out of it, trying sticking in another 1° of timing. Keep in mind that detonation can occur without you hearing the death rattle, so keep your eye on all the clues that would indicate you've gone too far. Adding more timing because you cannot hear detonation is walking the high wire without a net.
It's all about remembering a carb has different circuits, to accomplish different things, at different times. Idle mixture determined emulsion introduced at idle. Open the throttle blades and you transition from the idle circuit, to the accelerator pump circuit, to the main jet circuit. That's always the tricky one, because of the multiple transitions. But when you narrow down when a problem is happening and then think about what the carb is doing at that time, it gets easy to start applying your efforts where they will produce the most results.
Yes, there can be some gray areas, where you can fool a carb into doing something it wasn't really intended to do (Screaming Metal, did you ever lighten Holley accelerator pump weights?), but for typical street use, sorting carb issues is not rocket science. People usually create pitfalls by trying to over-think things.
Another thing to remember is when you are trying to zoom in on a problem area, don't make wholesale changes. If a car stumbles on acceleration, don't change fuel pressure, squirter diameters, pump cams and main jets, ignition timing and valve lash, all at one fell swoop, That is the simplest and fastest way to getting yourself down at the dark end of Lost Street. Change one thing at a time and then test the change. Did it help, or did it hurt? If it helped, try giving it a little more. If it hurt, put things back and test to be sure you are back to your baseline. Then go the other direction and see what happens.
All you are trying to do is to make the motor happy. But you have to listen to what it is trying to tell you, so you know what it really wants.
It's all about remembering a carb has different circuits, to accomplish different things, at different times. Idle mixture determined emulsion introduced at idle. Open the throttle blades and you transition from the idle circuit, to the accelerator pump circuit, to the main jet circuit. That's always the tricky one, because of the multiple transitions. But when you narrow down when a problem is happening and then think about what the carb is doing at that time, it gets easy to start applying your efforts where they will produce the most results.
Yes, there can be some gray areas, where you can fool a carb into doing something it wasn't really intended to do (Screaming Metal, did you ever lighten Holley accelerator pump weights?), but for typical street use, sorting carb issues is not rocket science. People usually create pitfalls by trying to over-think things.
Another thing to remember is when you are trying to zoom in on a problem area, don't make wholesale changes. If a car stumbles on acceleration, don't change fuel pressure, squirter diameters, pump cams and main jets, ignition timing and valve lash, all at one fell swoop, That is the simplest and fastest way to getting yourself down at the dark end of Lost Street. Change one thing at a time and then test the change. Did it help, or did it hurt? If it helped, try giving it a little more. If it hurt, put things back and test to be sure you are back to your baseline. Then go the other direction and see what happens.
All you are trying to do is to make the motor happy. But you have to listen to what it is trying to tell you, so you know what it really wants.
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