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Old 12-27-2010, 02:46 AM   #1
tx65coupe
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Default Edelbrock 1806 Carburetor Tuning

My 65 is still running a little rich. It has an Edelbrock 650 Thunder AVS carb. Its enough so that I get fuel residue on the outside of the exhaust tips and the bumper gaurds. The car runs really well though. I got this calibration kit. I think the jets need to be downsized a step. What size comes in it out of the box? Does anyone have any tips or advice for me?

http://www.summitracing.com/parts/EDL-1840/
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Edelbrock Top End
JBA Headers and Dynomax Ultraflo Mufflers

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Last edited by tx65coupe; 12-27-2010 at 04:41 PM.
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Old 12-27-2010, 08:32 AM   #2
Starfury
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You can't use the exhaust pipes as a gauge for how the engine is running. The engine is always running rich when you first start the car, so you'll likely always get some soot out the tailpipes.

Pull a plug and use that as a reference point. If it's black and sooty, try a rod with a bigger large (cruise mode) diameter. If it's white, go with a smaller diameter.
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Old 12-27-2010, 04:36 PM   #3
tx65coupe
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After I go somewhere I can wipe my finger inside the tail pipe and my finger is damp and sooty. There is raw fuel inside the tail pipe. I went on a 20 mile drive to my friends house and after I got there we did this test and got the same results. It was a warm day too.

I've never had a car leave fuel residue on the bumper gaurds before.

The exhaust always smells rich even when its hot outside and the car is warmed up. Alot of people comment that the fumes are too strong. You can't stand anywhere near the rear of the car while its running for more than a minute or your eyes will burn.

I have looked at the plugs and they look fine.

I have also checked the choke multiple times and it is working properly.

Fuel pressure is 6 psi.

Here is a quick question. How long should it take the fuel pressure to bleed down after the engine is turned off?
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1997 Cobra Convertible (stock)
1965 Mustang
Late Model 302, T5, Versailles 9 Inch
Edelbrock Top End
JBA Headers and Dynomax Ultraflo Mufflers

http://www.youtube.com/watch?v=LXk_MVV7V0g

Last edited by tx65coupe; 12-27-2010 at 04:42 PM.
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Old 12-29-2010, 04:38 AM   #4
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I was thinking about getting this Edelbrock 6593 air fuel ratio tool. I looked at the instructions and it says that it is supposed to be installed. I would rather use it as a temporary diagnostic tool.

http://www.summitracing.com/parts/EDL-6593/
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Late Model 302, T5, Versailles 9 Inch
Edelbrock Top End
JBA Headers and Dynomax Ultraflo Mufflers

http://www.youtube.com/watch?v=LXk_MVV7V0g
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Old 12-29-2010, 05:02 AM   #5
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Check the secondary lower butterflies and make sure they're closing all the way, if they're not the secondaries will drip.
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Old 12-29-2010, 06:24 AM   #6
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Dude, Edelbrock carbs are definitely not performance out of the box! I have the same carburetor and had the same problem. I used a vacuum gauge and did all of the above mentioned stuff with no avail. I just ended up taking my car to a dyno shop where the carb accounted for a 100hp loss to the rear wheels. The guys at the shop tuned the car by going to larger jets all around (Sorry I don't know what size they used). And the also changed out the metering rods twice. The Carb now runs like a million bucks.

Take the car to a dyno or do it the old fashion way of trial and error.
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Old 12-29-2010, 08:40 AM   #7
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Damp tailpipes don't mean anything either. Water is a natural byproduct of combustion.

But if it's smelling rich, then yes, something's definitely wrong. Doesn't mean it's your cruise mode, though, and the clean plugs support that. Could be your step-up springs are too soft (I'll cover that in a minute), or could be the power mode is too rich. And at idle you tune with the idle mix screws. The jets and rods don't really affect idle mix.

First thing's first, set the timing properly. If your timing's off, you'll be chasing your tail forever trying to get the carb dialed in. 8-10* initial, 30-34* total, all in by ~3k. That should get you in the ballpark.

Once the timing is set, set the idle mix. A vacuum gauge really helps here, but you can do it by ear as well. Once the idle mix is set, then worry about tweaking the rods/jets.

The one problem that I seem to notice with these carbs out of the box is that they tend to come with 7" step-up springs, which is a bit soft for many performance motors. The power mode kicks in too early, drawing too much fuel into the motor before it needs it. Drop a 4" or 5" spring in and it may help things a little.
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Old 12-29-2010, 07:09 PM   #8
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Quote:
Originally Posted by gconnsr View Post
Check the secondary lower butterflies and make sure they're closing all the way, if they're not the secondaries will drip.
I've seen this happen on Edelbrocks and had to tweak the secondary linkage, easy fix. Rear butterflies were opening a hair at idle do to slop and dripping.
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Old 12-30-2010, 05:01 AM   #9
tx65coupe
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Quote:
Originally Posted by gconnsr View Post
Check the secondary lower butterflies and make sure they're closing all the way, if they're not the secondaries will drip.
I did not even think about that being a possible issue.
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1997 Cobra Convertible (stock)
1965 Mustang
Late Model 302, T5, Versailles 9 Inch
Edelbrock Top End
JBA Headers and Dynomax Ultraflo Mufflers

http://www.youtube.com/watch?v=LXk_MVV7V0g
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Old 12-30-2010, 08:16 AM   #10
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Yes if the eyes are stinging you are dumping raw fuel. First thing you need to do is get correct fuel pressure. 4.5 psi is what those edelbrocks want. Not 6. Use a regulator. Once that is done check float levels and what was said about the secondaries. Your floats might be stuck. You usually see that when fuel drips out of the boosters. If you gave a vacuum gauge use that to set mixture and step up spring like starfury said.

Last edited by kalli; 12-30-2010 at 08:21 AM.
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Old 12-30-2010, 08:16 AM
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1806, 302, carb, edelbrock, ford, fuel, gauge, idle, intake, jets, mustang, pressure, problems, tuning, vacuum

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