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Old 05-27-2011, 04:14 PM
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Stupid Edelbrock carb question

I have an edelbrock 1406 carb on the 302 in my jeep. Should fuel be dripping from the brass nozzles in the primary boosters at idle? I just put a new needle and seat in it and adjusted the floats.

Mike

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Old 05-27-2011, 06:02 PM
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Quote:
Originally Posted by yeepman2
I have an edelbrock 1406 carb on the 302 in my jeep. Should fuel be dripping from the brass nozzles in the primary boosters at idle? I just put a new needle and seat in it and adjusted the floats.

Mike
It's common to see this but no they shouldn't be feeding at idle unless your idle is getting up over 8-900 RPM which might get them going because the throttle has been opened quite a ways to get airflow. If this is set this way then the idle to main transfer slots are probably below the throttle plate when they should be above it at idle. This is a big cam problem anything else with a mild cam would indicate other issues with cam and or ignition timing. To get the throttle blades positioned correctly with a big cam may require drilling of small holes in the throttle blades to meter idle air and still keep the blades closed enough to stay just under the transfer slot.

Another common problem with long duration cams or even large ratio rocker arms is that the idle vacuum falls below the point where the metering valve piston can keep the opening spring collapsed. If vacuum gets too low, then the spring lifts the metering piston to the power demand position which can result in the mains dribbling at idle. The solution is a softer spring to allow the lower vacuum to keep the power enrichment circuit shut off when it isn't needed.

The other possible issues besides float levels being too high could be excessive pump pressure, the Carter uses about 4 to 6 psi at the inlet fitting. More than that will force fuel around the needle and seat resulting in a higher fuel level in the bowl than you set with the float level adjustment. When teamed with a high output like 9 psi pump these carbs need a pressure regulator between them and the pump.

There are other possible issues but these get into pretty esoteric levels of tuning such as air correction jets and emulsion tubes, I mention it so you know they're there but this usually isn't a problem unless the carb is on a ragged top of the edge type engine that is hardly civilized enough to run on a drag track.

Here's a link to the Edlebrock tuning sight for this carb which has a ton of info. http://www.edelbrock.com/automotive_...ers_manual.pdf

Bogie
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Old 05-27-2011, 08:45 PM
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If it wasn't doing this before the needle valve/seat replacement and float adjustment, it's the float level or the needle valve's sticking open or clogged.

My money is on the float level being too high- it's easy to misjudge it, and it shouldn't have needed any but the smallest adjustment if it was correct w/the original needle valve.

INSTALLATION INSTRUCTIONS
http://www.edelbrock.com/automotive_.../1000/1400.pdf
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Old 05-28-2011, 07:17 AM
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Needle and seat new, verify the fuel pressure, float level there are two adjustments on that by the way. Then the next step would be to work with the step up springs , if the vacuum is low the tension of the springs will not allow the fuel rods to close, very common problem with low vac and lumpy cams.

The springs come in 3, 4, 5, 7, and 8-in. Hg. they are very easy to change and mess with. Two cautions, do not over tighten the screws and stuff a rag in the carb to avoid dropping the screws down the intake .........

When installing the fuel rods gently push them down into place, it you feel any resistance just back off a bit to allow, the spring and rod to align and get into place .. Not a big deal just fineness it don't get in a hurry. One more, new gaskets base and fuel bowl is also a good idea.
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Old 05-28-2011, 12:52 PM
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I've got a little more time this morning so here are some of the details. I've been running this engine, carb combo for about 10 years. It has a mild cam, I don't remember the specs, maybe just a little more than a rv cam.It was professionally jetted and set up back then and always ran pretty good. it was rebuilt and throttle shafts re bushed about 4 years ago, the last time I had to go through emissions,which I don't have to do anymore. Last fall it wasn't squirting fuel when the accelerator was pulled, so I rebuilt it and replaced the accelerator pump. It turned out I had a small leak in the fuel line just before the fuel pump so I fixed that. That's when this problem with the leaks at the booster showed up. I just put a new needle and seat in it and set the floats at 5/8" instead of 7/16" just to make sure the floats weren't set too high. I bent the floats where it says to in the edelbrock manual. I,ve been wondering about fuel pressure, but like I said I've been running this carb for ten years with the same fuel pump. The throttle plates being too far open makes a lot of sense, is there a way to check this?

Mike
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Old 05-28-2011, 01:56 PM
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I just pulled the cab and when I pulled the fuel line a lot of fuel came out of the inlet. There must be something I don't get about setting the floats, back to the manual.
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Old 05-28-2011, 02:28 PM
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ok, I just pulled another edelbrock 1406 from a firebird I have and it runs fine. I don't think the problems fuel pressure. And I guess some fuel should come out of the inlet when you pull the line.

Mike
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