Edelbrock models 1405 versus 1406 carburetors

[Billbo]

Hi all.

To whom it may be helpful.​

The 1406 carb is calibrated for ecconomy (lean).
This does not only mean the jets are the only parts that are different between the two carbs. From my researches the venturies are also different between the two carbs both in the primary and also in the secondaries.
The manual does not state this even though the sizes are identical in the specs.
What the difference is that the discharge holes (orifices) are smaller in the 1406 both in the primary and also in the secondary venturies. The air bleeds and idle jets on the venturi clusters are different also. All this rearrangement alters how the jets meter in the carb. Do not try to mimic the 1405 jetting on a 1406. It will not become simply a 1405 carb. You will be somewhere in the unknown as to where your mixture will be. Although the rods and jets are interchangeable, the calibration of the main body will cause the rods and jets to meter differently. I wondered why there are separate metering kits for each carb. Each kit has the appropriate rods and jets to suit each carb's upper and lower limits. If you look at the PDF manual. you must stay within the parrallel shaded area designed for the carb. Edelbrock has got these graphs pretty close. Unless you have an air/fuel ratio meter, you must follow the manual. I purchased a 1406 carb for my 360 and it was much too lean (surging lack of part acceleration). I should have purchased the 1405 instead but I wanted electric choke. I went to step No. 23 on the calibration sheet in the manual and performance improved dramatically. The sweet spot was to go up to step No. 19 in the manual. The carb is right on the money. Throttle response is great! Its a keeper. As far as the secondaries is concerned, wide open throttle improved with the primary enrichment. further improvement of the secondaries will need a dyno or some passes at a track. There is no sign of leaning out at wide open throttle. Spark plugs are light gray in colour which also tells a good mitxture.
I was worried that I went too rich but like i said the carb venturi clusters are different between the two and play a big role on how the rods and jets meter between the 1405 and the 1406 Edelbrock carbs.

Regards
Billy D..
Valiant VC 360 1967
Edelbrock LD4B manifold
10.5:1 compression
228/235 degs @.050

 

[Billbo]

I have revisited this thread since I have made a couple of mods which I would like to share.
In regards to the off idle stumble and the lean surging at low cruising, You can try the following. Before I stepped up the jetting to #23 and #19 according to the manual. This does work but in some cases the off idle stumble and lean light cruise still lingers. I have done the following. The idle jets on the 1406 are small about 36 thou orifice size. I drilled out the idle jets on the primary venturi clusters to about 45 thou. This totally fixed off idle stumble and light cruising. GONE. This allowed me to move back to stock jetting in cruise mode. In power mode I needed more fuel there so I use #2 setting according to the manual which consisted in a .095 jet in the primary with a 070/037 metering rod. If you look at the reference chart for the 1406 this will remain the cruise metering stock and increase the power metering by 4%. No flat spots, no stumble and excellent economy since we have gone back to stock cruise metering. Don't forget the idle circuit can contribute fuel metering at light cruise up to maybe 50mph. As far as the idle adjustment, unfortunately there is very little adjustment because of the larger idle jetting (which was drilled out). On a engine with a performance cam(low vacuum) this will benefit idle smoothness regardless of the lack of adjustment. I only have them out only 1/2 a turn. Idle is smoother than the any Holley I have had. So It does not worry me. The secondaries I have just used the primary jets .98 jets. (just swapped primaries with secondaries jets).
As far as the secondary bog is concerned, I have done a small mod to the secondary vanturi cluster by drilling a second transfer port no more than 1.5mm in diameter on the other side of the venturi which will transfer fuel a bit quicker during transition. Make sure you drill through one side of the tube aswell. This made a difference and the bog is almost non existent (but not comlpetely gone ale. Although I have not played with the pump shot yet) . Drilling this second port will not affect the main metering. Its just supports the transition. If it has no effect it wont hurt the carb. I have attached a photo of what I did.
Sorry to revisit this thread but I hope it will give you guys some ideas about this carb model.

Regards
Billy D.
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[YY1]

Thanks for sharing

 

[Aaron65]

Any pics on how you drilled out the idle jets? I accomplished the same thing by reducing the air bleed size for the idle circuit.

 

[pishta]

The suffix used to mean chevy ford or Mopar linkage. Was that Carter? also EGR and choke type.

this is great news as the Weber/Edelbrock/Carter/MagnettiMarelli has a rocky past with all its stumble issues.

 

[Billbo]

In regards to drilling out the idle jet, this was done with a hand chuck holding the venturi cluster steady while I drilled it at 0.8mm then 1mm. Took it for a drive and was all good so for good measure i gave it just a little more with a 1.1mm drill. All done by hand so you have control. Don,t use a drill. You will end up with excessive clearance. Closing the air bleed tends to fix the problem but you lose the emulsification of air to fuel which gives you nicer metering for idle.
Sorry I don't have any pics to show you.

Regards
Billy D...
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[Aaron65]

By the idle jet, do you mean the one that protrudes from the bottom of the venturi cluster, or the idle feed restriction, which is behind the pressed in air bleed on the side of the venturi cluster?

 

[Billbo]

The one that protrudes from the bottom. Not the idle feed restriction.

 

[Aaron65]

Cool, thanks! I've read about a guy who removes the brass air bleed and drills out the restrictor, but that always seemed like a dodgy surgery to me. Luckily, I have a junk 1406 sitting around that I can try drilling the jet on.

 

[Billbo]

If you drill the restrictor you will let in more air from the first air bleed leaning the mixture out more. Lightly skim the idle jet. Depending on the engine you may need less drilling. Be very carefull. Try and do it in very small increments. I think 1mm is a good size. But see how you go.

Regards
Billy D...
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[Hysteric]

Hey Billy.

I noticed you haven't mentioned anything about playing with the air valve door weight or the attack angle of the blades.

These would be the 1st and 2nd places i would begin to play with to get the smooth transition from the primaries to secondaries.

Also you can drill and tap the air bleeds to accept holley style air bleeds making it easier to try different calibrations to see what your motor likes. My understanding of the edelbrock carbs is that they are a chev generic calibration and so need work to suit other engines.

I would look at working with the original design ie changing ifr's and iab's sizes before starting to drill any new holes and change the original design parameters.

You can also find old 625 carters from the pre Federal Mogul era and study the calibration of the carbs and compare to yours and swap boosters out and so forth. When you look at the earlier carbs you'll understand what i'm talking about.

Hysteric

 

[Hipo65]

Heres some more helpful info on ridding the motor of the classic secondary bog! (sorry spelling is gonna suck LOL!) I cured my 1405 on my 273 totally of the "bog" & now frys tires! I also installed an AEM wide band o2 gauge this my friends is the only way to dial in any carb on any car HANDS DOWN! noticed rite off the bat it was lean everywhere except idle 12-12.7 in gear. Once I got the cruise A/F around where it ran the best @ its leanest crusie for my little hi-po 273 it seems to be happy @ no leaner (leaner cruise metering rods same power step from 65x52 to 68x52 than 14.5-15.0 @ cruise. Then WOT was fat so a simple jet change (down to.083) got the WOT to 12.5! then that matha f#!*ing BOG......! on the o2 meter it would go off the scale lean when you would hammer it,i figured that but was shocked it went off the scale (gauge quits @ 19.9! then just shows 3 flat lines!) 1st thing I did was give it as much acc pump shot as possible... no dice still stupid lean when hammering it. Next I ground the lower edge of the secondary counter weight to give the air valve more attack angle (flatter at rest) helped ever so slightly,but still off chart lean when floored. So I had an old 800cfm eddy I got from kinda my brother in-law of sorts that he didn't want it anymore cuz he went fuel injection on his 455 buick. I opend it up to see the counter weights were heavyer on the top than mine & the acc pump has a mean spring on it compaired to my 1405,sort of like the marine carbs have. So I ground the weights on it to give flatter attack angle then it had & installed the acc pump to. at this point I also inlarged the acc pump discharge nossles to .035 holes ( I know eddy sells a kit with 3 different shooters but im cheap & have tiny drill bits!) Once back together that's when it started to make some diffreance! from off idle (not moven) it was gone!!!! but come back when cruisen @ apx. 40 mph & up RRRRRRRR!!!!!! & went off scale lean again. What ended up totally ridding the bog was I pulled the secondary clusters removed the early feed tubes in the secondarys ( the small tubes) peened the main air bleeds smaller to about 1/2 the stock size to give stronger signal to the boosters. I also noticed that the the eddy 800 secondary clusters had a brass plug in what would be the air blead for the secondary initial discharge port. I thought hum no air bleed would make it pull more fuel instead of air on the initial opening of the secondarys. So I plugged them off & put it back together & PRESTO!!!!! This little 273 has NEVER had that kind of throddle responce! EVER! I kept blaming the stock single plane for the low power off idle even with the stock carb! I shelfed the stock carb because I cannot find any 3 step rods the tune it & the eddy has the 3/4 inch acc pump well where as the stock afb has only 11/16 well (even less pump shot) I hope it helps you guys with your AFB/eddy carbs (completely change how the lil 273 runs!) a little time & man they can work real nice! but above all get a wide band o2 gauge! quit guessing! Feel free to ask qustions & ill get pics of mods if anyone wants them.

 

[moe7404]

i haven't been keeping up with the thread. but on 2-3 step rods. dont for get you do have a file in your tool box. you might get what you want by filling the rod some. all you need is mike to measure the flat spot. way back when i even calculated the % of change. but never got that into my computer program.

 

[Hipo65]

The 3 step rods sit higher than the 2 step rods & the jets are taller as well. There is a whole lot more rods & jets ava for 2-step then there is for 3 step ( I wont pay for what is wanted for the 3 step stuff!) where the 3 step rods start to go leaner is a good .025-.030 diff from the 2 step rods. Again my little charger 273 has never ran this good with the stock AFB as it does now with the "tuned correctly 500 eddy" The ONLY way to tune any carb is via wide band o2 gauge! Best tool for this since canned beer! Not high jacken thread but I have spet a lot of time tryen to "cure" the secondary bog that thease carbs are known for & won the battle!!!! & this is how I did it above. The only problem with filing rods is if you go to far there isn't a surplus of them just laying around to try again. (at least for me there isn't)

 

[Aaron65]

I wouldn't mind seeing pics of your modifications if you have them. Sounds interesting!

 

[Hipo65]

Aaron65, Ill get some up today! the only one I wont be able to get you is the accelerator pump out of the eddy 800 I swapped. But other than the material that the cup is made of its the same as the accelerator pump that goes into the marine carbs. The marine carb accelerator pump is what I was going to order until I diceded to canableize my free eddy 800!

 

[pishta]

did the marine pump have a different cover, like sealed? That pump shaft assy is what you need for a Carter-brock blow through too.

 

[Hipo65]

phista,i don't think so on the cover but it does have a real heavy spring on it just like the 800 eddy so when mashed quickly it wont compress the spring instead it push's fuel out now! im gonna post some pics & this stuff works great for tighter converters with 3.23 gears & a tiny motor (low air speed when hammered will require more raw fuel to pick its self up & make a crisp smooth transition to wot). Again cant say enough tune via wide band o2 gauge! it will squash out all guess work!

 

[Hipo65]

First after giving as much acc pump shot as possible id changed the attack angle of the air valve in the secondaires. By grinding the "at rest " postion of the weights to make it pull harder 1st instead of just flop rite open . shown with a stock un modded eddy 600 weight for comp. Modded one is on the right. & to reattach them push on square & one small tack weld & DONE!

 

[Hipo65]

Then I stole the counter weights out of the eddy 800 because I seen they were heavyer in the rite spot to delay opening even more. Notice I also grinded the 800 weights to because its attack angle was steep too.

 

[Hipo65]

Then what started to make the diffreace ( at this point I had also installed the accelerator pump from the eddy 800 aswell) was when I butsted out my trusty tiny drill bits & opened up the discharge nossle's to .038 of an inch. That took care of it from a stop but returned when stomping it from cruising. (hint, the A/F @ idle in gear was 12.0-12.5 so was already a little rich to help the transition to WOT) now @ cruise it was 14.5-15.0 a lot leaner & would bog when hammered.

 

[Hipo65]

Here is what WON the bog battle all around!!!! 1st 2 pics are stock secondary clusters. notice small tube its the early feed fuel supply tube/restriction. even in my old carter AFB tuning book it says to help cure secondary bog to remove the tube's to give more fuel to the early feed circuit. The last thing I did was plug the air bleed for it aswell,the eddy 800 has them plugged solid from the factory with brass plugs.

 

[Hipo65]

Here are pics of the air bleeds the stock 500 & then the stock 800. So I plugged the 500 bleeds too & put it back together. Not only does it fry tires though an intersction now,it also don't bog when floored from 50 mph & leaner cruise A/F ratios anymore! what this did was give even more fuel to the initial discharge port as soon as the secondary's are opened. (see pic) Made a HUGE diff in how this car runs! it never ran this good with the stock AFB EVER! Again no trying to hijack thread but this is how I cured my secondary bog! Via wideband o2 gauge!

 

[Aaron65]

Thanks! I use an Innovate MTX-L to tune my stuff, and I'm running a 1406 on my Mustang's 289. It's set up pretty well, but occasionally I'll get a bog (it seems to depend on weather conditions).

I have noticed that it's pretty fat at heavy and full throttle (12-12.5:1), but does lean out a bit when hitting the gas, but nowhere near dead lean like yours did. I love to tinker though, so you have some interesting, proven solutions.

 

[Hipo65]

I had that same meter in my old 76 drag dart! I like the AEM for it is super easy install. & 12.0-12.5 itsnt to bad @ all for a WOT A/F raito man,thats about all the leaner you wanna go for WOT max power for a carb. Your rite weather & temp come into play for sure. That's why im leaven it be until nicer weather is here! its a bit lean now but when temps go up it should be balls on! for cruise A/F raito. But bog is gone! yay!