Edelbrock Carburetor tuning question...

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RustyRatRod

RustyRatRod

I was born on a Monday. Not last Monday.
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I have an older Edelbrock 625 CFM AFB style carburetor. It still has the Carter Competition series number it is such an early production carburetor. Anyway. it is on my 75 Ford F250. 351M engine, stone stock. I just changed out the plugs. All of them were white like it is running lean. What would be a good step up as far as a metering rod change? The carburetor is still stock and unmodified. Thank you drive through.
 
Personally I would go at least two steps up on the whole rod for white plugs, IF you are fairly sure it's through the entire throttle range.
Does it act "peaky" at low throttle or surge at all?
If not you might just go with a rod that has a smaller top size and leave the lower end the same size.
Obviously there are jets and crap that can alter this through the entire off idle range also, so it would be nice to try to find out if it's just at mid, high, or low throttle only.

Sorry, I meant two steps down (in size) but you probably already knew that. :D
 
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Nope no surgin at all. It is fairly cold natured though. I know that might indicate it is too lean as well. It has a choke but it is not hooked up. Doesn't get real cold down here you know. No drivability qualms at all. The plugs just seem to indicate a lean mixture.
 
Can you read the number on the metering rods? The 1406 comes with 7547s, and if that's the case, I'd step up (ha ha) to a 7147.

Is the truck surging at cruise or on medium acceleration? If it's not, you're probably fine. Modern gas doesn't color the plugs much.
 
Well I cannot brag enough on how it runs. It runs great. No bog whatsoever......but then, I rarely ever stab it. Even on the rare occasion, it does not hesitate at all. I just want to make sure the mixture is about right and from the plugs, it is not. I will see if I can tell which rods are in it.
 
Reading plugs with today's fuels is a crap shoot. If you really want to dial it in,some form of a/f ratio, wideband gauge is your best bet.
 
Johnny Dart said:
Reading plugs with today's fuels is a crap shoot. If you really want to dial it in,some form of a/f ratio, wideband gauge is your best bet.
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Yeah that aint in the budget. lol
 
Would it be worthwhile to do a wide open throttle chop and see what they look like at wot?
I usually start with mains and go backwards from there. I'd go up a couple main jet sizes and see how it runs, then pull the plugs after some regular street driving and see what to do with the needles.
Just my .02
 
My experience is they run lean from eddy factory. Like the one on my Duster, purrs like a kitten driving it around. And there is no bog if it breaks the tire loose. But if you nurse the take off so to not spin the wheels, she'll cough, sputter, and hesitate. I don't understand why all customers have this complaint and eddy still shells them out like this.
 
318willrun said:
My experience is they run lean from eddy factory. Like the one on my Duster, purrs like a kitten driving it around. And there is no bog if it breaks the tire loose. But if you nurse the take off so to not spin the wheels, she'll cough, sputter, and hesitate. I don't understand why all customers have this complaint and eddy still shells them out like this.
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Exactly my experience with them also, and had to go up I think it was 4 jet sizes all around and I live at 5,500 feet.
 
jos51700 said:
Would it be worthwhile to do a wide open throttle chop and see what they look like at wot?
I usually start with mains and go backwards from there. I'd go up a couple main jet sizes and see how it runs, then pull the plugs after some regular street driving and see what to do with the needles.
Just my .02
Click to expand...

That's probably not a bad idea.
 
RustyRatRod said:
That's probably not a bad idea.
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My Edelbrock experience is that they're fine, if not a little rich, at full throttle, but lean on the primary and idle circuits. Therefore, full throttle runs probably won't help. Going up four jet sizes on the primaries is a big swing on one of these. Of course, all cars are different.

Alternatively, the manual choke models are richer from the factory, and they tend to be TOO rich on the primaries.
 
Leave the rods alone and go up one primary size, 98 to 100,that might be 1405 jetting and 1406 might be 96-98, its only been 15 years since rejetting one.
 
FWIW, just an observation.....I have been getting back into the carb scene after an absence. Reading the plugs with the new fuels just does not seem to work like it did 20+ year ago. My son's 340 plugs (with HEI) come out scarily clean no matter what. But we put an AFR meter on it a week or so ago, and it is overall running rich at light cruise and lower RPM's (when it is on the idle circuit) and the highest AFR we see is about 16 at 55 MPH, going down a slight grade....where I would expect it to be a bit lean. But the plugs show no color on the porcelain.

Until I learn to look waaaay down at the porcelain base and read plugs, I am not going to trust my old plug reading for tuning with the new pump fuels. BTW, we are using Shell Premium.
 
nm9stheham said:
FWIW, just an observation.....I have been getting back into the carb scene after an absence. Reading the plugs with the new fuels just does not seem to work like it did 20+ year ago. My son's 340 plugs (with HEI) come out scarily clean no matter what. But we put an AFR meter on it a week or so ago, and it is overall running rich at light cruise and lower RPM's (when it is on the idle circuit) and the highest AFR we see is about 16 at 55 MPH, going down a slight grade....where I would expect it to be a bit lean. But the plugs show no color on the porcelain.

Until I learn to look waaaay down at the porcelain base and read plugs, I am not going to trust my old plug reading for tuning with the new pump fuels. BTW, we are using Shell Premium.
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This is the way it is. The plug "ring" or base will still show a little color, so if that has some soot on it, you're probably good to go.
 
First thing I do with and eddy is check vacuum and put the correct step up springs in. Nothing else matters if it can't move rods at the right time
 
fklskv said:
First thing I do with and eddy is check vacuum and put the correct step up springs in. Nothing else matters if it can't move rods at the right time
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This is where I am. I have bigger squirters in my 600. I got them from a 750 that was junk and giving to me for free. I have the accelerator pump on the richest setting also. this has helped a lot, but I have ordered the step up springs for 12 bucks. This is my last attempt to cure, then I'm swapping to a Holley.
It's a shame that the whole classic car industry is trying to deal with this "bog" in the eddy's, yet eddy seems to have no knowledge or the will to do anything about it.
 
318willrun said:
This is where I am. I have bigger squirters in my 600. I got them from a 750 that was junk and giving to me for free. I have the accelerator pump on the richest setting also. this has helped a lot, but I have ordered the step up springs for 12 bucks. This is my last attempt to cure, then I'm swapping to a Holley.
It's a shame that the whole classic car industry is trying to deal with this "bog" in the eddy's, yet eddy seems to have no knowledge or the will to do anything about it.
Click to expand...

Have you ever done an A/F ratio test ?
Do you have any idea what your A/F ratio is at idle, cruise, wide open ?
How about fuel pressure at these stages ?
What makes you think you have to go richer, or grab the parts off a 750 to make it run better ?
Just wondering if you have sound proof on which way you need to shoot, or are you just taking a shot in the dark ?
With all the missed matched parts from 750 etc, your carb is way out of wack. If I were you I would set everything back to the box stock settings. Jets, springs, rods.
As long as you have the right matched carb for the application, Edes generally run pretty well with the factory settings, give or take a couple small tweaks.
These Edes are generally the easiest carbs to set up. Unless you have alot of experience with Holleys, they are not going to be any easier.
 
:eek::eek:
Johnny Dart said:
Have you ever done an A/F ratio test ?
Do you have any idea what your A/F ratio is at idle, cruise, wide open ?
How about fuel pressure at these stages ?
What makes you think you have to go richer, or grab the parts off a 750 to make it run better ?
Just wondering if you have sound proof on which way you need to shoot, or are you just taking a shot in the dark ?
With all the missed matched parts from 750 etc, your carb is way out of wack. If I were you I would set everything back to the box stock settings. Jets, springs, rods.
As long as you have the right matched carb for the application, Edes generally run pretty well with the factory settings, give or take a couple small tweaks.
These Edes are generally the easiest carbs to set up. Unless you have alot of experience with Holleys, they are not going to be any easier.
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Well, I will tell you like this. In stock form, it would completely die when punched at a dead idle. Now, with the accelerator pump on "rich" and the 750 squirters in there, it doesn't "die", but is still somewhat flat. No A/F ratio, no fuel pressure gage, no sound proofing, but my "shot in the dark" has helped it considerably. I would like to take another "shot in the dark" with step up springs. If this don't work, I'll throw a "shot in the dark" Holley at it and I bet it will work perfect! But shoot, my whole project is a mismatched "shot in the dark" 318. I mean, 340 cast intake on 318 heads is mismatched, and a 100 dollar cam, I didn't degree it either, it was a shot in the dark, and using a socket and a screw driver to bench flow the dremeled heads, that was a shot in the dark. Without headers, stock converter, 2.76 gears, it ran 94 mph (better than a perfectly matched from the factory'73 340 duster with 3.21's. You know what they say, it's better to be lucky than good (hope you have a sense of humor)... LOL
 
318willrun said:
:eek::eek:
Well, I will tell you like this. In stock form, it would completely die when punched at a dead idle. Now, with the accelerator pump on "rich" and the 750 squirters in there, it doesn't "die", but is still somewhat flat. No A/F ratio, no fuel pressure gage, no sound proofing, but my "shot in the dark" has helped it considerably. I would like to take another "shot in the dark" with step up springs. If this don't work, I'll throw a "shot in the dark" Holley at it and I bet it will work perfect! But shoot, my whole project is a mismatched "shot in the dark" 318. I mean, 340 cast intake on 318 heads is mismatched, and a 100 dollar cam, I didn't degree it either, it was a shot in the dark, and using a socket and a screw driver to bench flow the dremeled heads, that was a shot in the dark. Without headers, stock converter, 2.76 gears, it ran 94 mph (better than a perfectly matched from the factory'73 340 duster with 3.21's. You know what they say, it's better to be lucky than good (hope you have a sense of humor)... LOL
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You can sink a boat with a machine gun without ever putting a hole it if you just fill it up with lead. :D
Smart *** I know, but seriously you do a lot of this stuff and have a good base for estimating from what I have seen and read.
 
Just like to laugh a little now and then....
 
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