Edelbrock Experts I need your thoughts

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straightlinespeed

straightlinespeed

Sometimes I pretend to be normal
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I've been playing around with an Edelbrock 1406 on my car. Im curious about the jets and rods sizing. I've been playing around with different combos for my car, just to try to understand how these work together. Which got me to thinking.

Stock main jets are .098 and 75/47 Rods. Which is 23/51 (Im getting this by subtracting the metering rod sizes from the jet size). Which is the actual orifice opening either at cruise or power. Correct?

I went to .092 and 68/42. Which is 24/50

Now in my mind this is a very similar combo if I understand this correctly. So my question is since they are almost identical does it matter if my main jet is larger or smaller? Either way I get almost the same A/F readings. Does this make sense? Its kind of hard to explain by typing.

My other question is... Is it normal for Edelbrocks to lean out as you roll into the throttle? For instance say Im driving at 60mph and my A/F is 14.2-14.7. I roll into the throttle fairly heavy but not enough to get into the power side. My A/F will creep up to as high as 16.7 depending on how hard Im pushing on the throttle. Just wondering if this is a common thing.
 
98/75 is much larger than 92/68
think of the outside 1/8 inch of a 1 inch circle compared to the outside 1/8 inch of a .90 circle.I think if you increase the diameter of a 1" circle 1/8" you increase the area about 25%...you have leaned a very lean carb even more.
That 1406 is very lean compared to the 1405.Edelbrock supposes the 1406 with its electric choke will probably find its way on daily drivers (read fuel efficiency) and the 1405 manual choke being much richer is for racers.
..light acceleration will always lean out because the air is drawn in much quicker than the gas...expect 15. 16.5 briefly
...even though i responded i am far from an expert!
 
Last edited:
The 1406 is an economy carburetor. The 1405 is the performance version. You cannot tune economy out of the 1406 because there are many differences. There's a thread around here somewhere that tells all about it.
 
The 1406 is only 2% leaner than the 1405 (not enough to matter in this application).

The issue you are experiencing is when you push into the throttle, not while cruising. Therefore you probably need to adjust the accelerator pump calibration to compensate for the airflow change and keep the fuel delivery at the optimal level when you do.

Accelerator pump.jpg
 
RustyRatRod said:
The 1406 is an economy carburetor. The 1405 is the performance version. You cannot tune economy out of the 1406 because there are many differences. There's a thread around here somewhere that tells all about it.
Click to expand...
Yep, this I know. I've got that thread saved to my bookmarks. Im not going for performance, Im just trying to tune it better for my car. Im just trying to wrap my head around the jets/metering rods. I've spent the last week reading, but havent run across this in my reading and I want to know if Im thinking the correct way.
 
The 1405 uses the following jets/rods...

Metering Jets - Primary .100, Secondary .095; Metering Rods - .070 x .047

The 1406 uses the following jets/rods...

Metering Jets - Primary .098, Secondary .095; Metering Rods - .075 x .047
 
straightlinespeed said:
Yep, this I know. I've got that thread saved to my bookmarks. Im not going for performance, Im just trying to tune it better for my car. Im just trying to wrap my head around the jets/metering rods. I've spent the last week reading, but havent run across this in my reading and I want to know if Im thinking the correct way.
Click to expand...

Your engine is very much a performance engine. The 1406 may not be tuneable for you. That's what I was trying to get at.
 
Is the lean mixture effect momentary like a flat spot just after going into the pedal, or sustained weakness?
 
Ddaddy said:
The 1406 is only 2% leaner than the 1405 (not enough to matter in this application).

The issue you are experiencing is when you push into the throttle, not while cruising. Therefore you probably need to adjust the accelerator pump calibration to compensate for the airflow change and keep the fuel delivery at the optimal level when you do.

View attachment 1714947352
Click to expand...
Thanks Dave, I already did that adjustment and it took a lot of the lean bog out of it when I hammered on it. Not all of it, but I would say 85% of it. That is another issue I have to work on
 
RustyRatRod said:
Your engine is very much a performance engine. The 1406 may not be tuneable for you. That's what I was trying to get at.
Click to expand...
Oh sorry, I gotcha now! I did find a thread about some modifications I could make to it, but I would rather get one of the AFB carbs if that is the case.. I dont want to mess up a carb that someone else could use. I do have to say, though if Im just cruising around (easy on it) with this carb, the car runs great, is smoother, and my fuel mileage is much better.

Darthomas said:
Is the lean mixture effect momentary like a flat spot just after going into the pedal, or sustained weakness?
Click to expand...
It starts leaning out as soon as I start pushing on the throttle and will keep raising as long as I keep pushing. Until either I get into the power side or I stop pushing. I've seen it from my cruise A/F to about 16.7 with a heavier pedal.

Now the WOT is another issue. If I hammer on the throttle it will go instantly lean (off the meter lean) until the fuel catches up, then its perfect. 12.5-13.0. If I roll into the throttle then mash on it I only get a lean spot for a split second usually the meter is around 16.7-17.
 
straightlinespeed said:
Thanks Dave, I already did that adjustment and it took a lot of the lean bog out of it when I hammered on it. Not all of it, but I would say 85% of it. That is another issue I have to work on
Click to expand...

Try this combo...
Metering Jets - Primary .095, Secondary .098; Metering Rods - .065 x .047

I think the secondary jets are where the biggest part of the issue lies.
 
ir3333 said:
98/75 is much larger than 92/68
think of the outside 1/8 inch of a 1 inch circle compared to the outside 1/8 inch of a .90 circle.I think if you increase the diameter of a 1" circle 1/8" you increase the area about 25%...you have leaned a very lean carb even more.
That 1406 is very lean compared to the 1405.Edelbrock supposes the 1406 with its electric choke will probably find its way on daily drivers (read fuel efficiency) and the 1405 manual choke being much richer is for racers.
..light acceleration will always lean out because the air is drawn in much quicker than the gas...expect 15. 16.5 briefly
...even though i responded i am far from an expert!
Click to expand...

Im not doubting what your saying here. Im just telling you what my A/F meter was telling me. Both sizes that I mentioned above where almost identical on my meter. The 92/68 wasnt any leaner than the 98/75. In my mind I think respectively the hole sizes, when the rods are in them are about the same size.
 
Ddaddy said:
Try this combo...
Metering Jets - Primary .095, Secondary .098; Metering Rods - .065 x .047

I think the secondary jets are where the biggest part of the issue lies.
Click to expand...
I've considered flip flopping the jets, I read on another forum that someone tried that and had good results. It cant hurt to try.
 
I agree with Ddaddy putting in a metering rod like that will reduce the step from cruise to power and should help smooth out the throttle transitions. I think that leaning out you get when you gradually open the throttle is the actual mixture you're getting just through the cruise mixture on the primaries, which is too lean. I would first try the 65x47 rods (much easier/quicker) and see how far it changes the AFR and if it needs to be richened back (probably on the power circuit) then put in the .095 primary jets.

Anybody got a link to that thread comparing the 1406 and 1405?
 
MOPEkidD-3 said:
I agree with Ddaddy putting in a metering rod like that will reduce the step from cruise to power and should help smooth out the throttle transitions. I think that leaning out you get when you gradually open the throttle is the actual mixture you're getting just through the cruise mixture on the primaries, which is too lean. I would first try the 65x47 rods (much easier/quicker) and see how far it changes the AFR and if it needs to be richened back (probably on the power circuit) then put in the .095 primary jets.

Anybody got a link to that thread comparing the 1406 and 1405?
Click to expand...

Here is the link I had saved. Another 1405 vs 1406 thread

Ddaddy said:
Try this combo...
Metering Jets - Primary .095, Secondary .098; Metering Rods - .065 x .047

I think the secondary jets are where the biggest part of the issue lies.
Click to expand...

After thinking about this combo more. I have the feeling Im going to be way to rich on the cruise circuit. I had the 98 jets in with a 71/47 rod and my A/F was in the 11's. I have the feeling if I go to a 95 jet and a 65 rod its going to be worse.

Here are the combos that I've tried so far and the rough A/F readings each.

Stock 98-75/47 A/F 14.0-14.5 WOT A/F 12.5-13.0
98-73/47 A/F 13.3-13.8 WOT A/F 12.0-12.5
98-71/47 A/F 12.7-13.0 WOT A/F 11.2-11.7

101-73/47 A/F 11.0-11.7 WOT A/F 10.0-10.3

92-68/42 A/F 14.0-14.5 WOT A/F 12.5-13.0

Now all the combos above (with the exception of the 101-73/47) started to lean out the second I stepped on the throttle. The richer the combo in the cruise circuit the less it leaned out. The other odd thing is with the first 3 tries, even though the power side stayed the same size, it got richer.
 
straightlinespeed said:
Here is the link I had saved. Another 1405 vs 1406 thread





Here are the combos that I've tried so far and the rough A/F readings each.

Stock 98-75/47 A/F 14.0-14.5 WOT A/F 12.5-13.0
98-73/47 A/F 13.3-13.8 WOT A/F 12.0-12.5
98-71/47 A/F 12.7-13.0 WOT A/F 11.2-11.7

101-73/47 A/F 11.0-11.7 WOT A/F 10.0-10.3

92-68/42 A/F 14.0-14.5 WOT A/F 12.5-13.0

Now all the combos above (with the exception of the 101-73/47) started to lean out the second I stepped on the throttle. The richer the combo in the cruise circuit the less it leaned out. The other odd thing is with the first 3 tries, even though the power side stayed the same size, it got richer.
Click to expand...

...all you have changed is the cruise circuit which has gone richer as it should.
stock looks perfect.
...have you tried a different step up spring?
 
downsr said:
Get rid of it and get a holley easier to work on if you need to
Click to expand...

Thats what I had on it. The Holleys have there own set of issues IMO. This isnt about which one is better, or easier to work on. I've spent the Spring playing with the Holley, and I understand the tuning on them. Its now time to play with the Eddy and Im just trying to make sure I understand the tuning techniques of these. Oh and IMO the Eddy is way easier to work on, but tuning is another story.

ir3333 said:
...all you have changed is the cruise circuit which has gone richer as it should.
stock looks perfect.
...have you tried a different step up spring?
Click to expand...

I tried the Natural and Orange spring. All of the above combos are with the Orange spring.
 
just curious,what is the rest of your build.I have a stock cam 340 now that is running rich at cruise (1405) and have just ordered metering rods to lean the cruise circuits.
The 1405 has richer cruise circuits than the 650 Thunder as well which I have used and really like.
 
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