Rich Edelebrocks

I am running 2 500 CFM Edelbrock carbs on my 1st Gen 392 Hemi. They are running so rich, they are eating up spark plugs like they were pop corn.
A mechanic friend of mine says nothing can be done, it's the natuer of running 2 4's. I don't want to accept that. Any suggestions to improve, or eliminate this situation?

Number on the carbs??

Edelbrock sells a set calibrated for dual quad setups. I bet you don;t have that.

http://old.edelbrock.com/automotive/mc/carburetors/thunder.shtml

Calibrations are listed verify what you have.

Will check to confirm, but I am almost positive mine are the Performer series? I've had them for about 4 years?

Both are 8867, but one has electric choke? On the base plate of each, is stamped F 2 X 4.

my eddy 1406 was lean & the choke came off way too fast. check your needle/seat(s). waterlogged float(s). float hanging up. fuel psi

When adjusting fuel/air mixture, should both carbs be excatly the same, or adjust as individual carbs?

Both carbs HAVE to be synced or you will never get them to work right. It take patience and a bit of trial and error to get right. This Guide will help you and save me from typing it all out. Running rich is bad and your buddy should feel bad for that mistaken advise. Having one carb rich and another lean is worse. A broadband a/f gauge is a very good tool, but you should be able to get close without one. YouTube has vids to help out as well. HTH, Steve

Thanks a ton. I have a Hemi with a cross ram that is way out of tune. I was looking for a document like this as doing some tuning is first thing on my list this spring. I was pretty good at tuning a single four and did a pretty good job with the 6 pack (found the guide from someone here). Moparts comes through again.

Great info. Something I think even an idiot (that would be me) can understand, and do. Thanks.

Are you running them with both working at the same time, one to one linkage, or with progressive linkage?
You probably need to lean down the metering rods on the primary step, the bigger step up high, to get it to run good at light part throttle cruise
I would adjust the primary idle mixture screws so it is as lean as possible and still start and idle okay with no stumble from driving away from a idle.
What spark plugs brand and part numbers are you using now and how much compression on your motor?
The new Eddy carbs are not as good as they use to be
You can get them to work excellent with enough tuning, so good they should knock the tires off at will at WOT

One to one, come in together.
NGK plugs/Autolite 65.
The car runs and idles good. Exhaust tips black as coal, exhaust will burn your eyes, and foul the plugs. I just replaced the Autolite 65 with the NGK equivalent, but I don't remember the number.

i'm running two 600's on a ch28 and they work great. the 500's have a very restrictive primary booster, and you could be getting too strong of a vacuum signal to them. you might try a 68x52 rod; also do a fuel pressure and float level check. long cams will screw up the metering system too. in my opinion those 500's belong on small engines only. that primary cluster is just too screwed up to put on anything that will flow air. back in the day carter had a properly done small afb. instead of using the carter model, that required more part changes, edelbrock got cheap and just restricted the front half. I believe it is possible to put 600 clusters in those carbs. be careful of bad advice!!!!!!!!!

I started with 650's. Too much carb, switched to 600's. Too much carb, went to the 500's. Runs much better. 2 X 500 = 1000, that's a lot of cfm's. The engine is mild, only bored 30 over to clean up the block, and mild cam. Stock iron heads, stock exhaust manifolds, factory Weiand intake. I built it to drive, not to race, or win trophy's or burn out contest.

Try tuning the primary rods on the large step by making it larger in diameter by .002 to .006 or so and see if that helps, keep tuning it until your happy
How much timing at idle and how much total timing?
I cut my teeth( a long time ago back in the early to mid 1960s) on tuning the first gen Hemi Chrysler Firepower motors, 331,354 and 392 300 letter series motors
Good luck

Fuel psi is critical. IIR Edelbrocks cannot have more 6 psi.

I'm running 4 psi, Holley electric pump, Moon Eyes gauge. I lean toward the old stuff, moon eyes, stewart warner, etc. I also name my cars (car now). It's a 48 DeSoto, named Odd rOd. The O's are capital letters, and they are painted (no decals) like the moon eyes.

a carb cannot make 0ne cfm. cfm ratings are for dummies. you've got something wrong besides the carbs.

I had once bolted a Marine dual quad intake on a 440 with 2 brand new 625cfm Carter carbs, and that engine was a blast to drive.
Just some tweaking of the idle mixture screws was enough to get them to idle nicely. No issues whatsoever.




Many years later I installed two 650 used but otherwise equal Carter/Edelbrocks on a 354ci Chrysler poly-engine with a 392ci Hemi dual quad intake, and the engine ran very rich and backfired at the same time occassionaly. The carbs where jetted equally and checked for vacuumleaks but none were found. Something was not happy in that setup. After a while I switched back to a single carb as I just wanted to drive the car at the time.

8867 isn't the carb number.

the carb number is stamped as below

Only number. I checked there first, only numbers there was the F 2X4. The 8867 was stamped on top plate, left rear (driver side).

Something is real fishy about that.

Edelbrock used (1)1403 and (1) 1404, the difference being one of them had an electric choke, for their dual quad setups when they used Performer carbs.

1403 P jets .086" S jets .095" Rods .065" x .052" spring orange (5")
1404 P jets .086" S.jets .095" Rods .065" x .052" spring orange (5")

They used 1803 and 1804 for the AVS dual quad setup.

1803 P jets .086" S jets .077" Rods .065 x .057" spring orange (5")
1804 P jets .086" S jets .077" Rods .065" x .052" spring orange (5")

MIght need to measure things and see what you really have and compare it to the Edelbrock dual quad cals.

Stupid thought?? Can I just change the S jets to .077 and spring on 1403 to .057 (assuming mine is a 1403 & 1404} ?

Tried your "This Guide". Could defiently tell a difference, but still seems a little rich. Raining here, so I didn't test drive it yet. Probably needs more fine tuning. Patience may be my greatest weakness .

Remember most 2 four setups are progressive linkage so at one to one are way too rich unless running wide ipen.


The s jets are the secondary jets and unless you're rich at wot that's not the problem. If you are rich at wot changing the secondary jets will help. For each 4% leaner move you want decrease the whole by .003. It's listed on page 14 of the tuning chart. The primary jet is bigger because the metering rod goes inside the hole. The rods have two sizes on them they move up and down to increase or decrease fuel.

They first thing you have to do is find out what carb and what size jets and rods are in them now. Here https://static.summitracing.com/global/images/chartsguides/e/edl-1400_fm.pdf look up chart for the number carb you have and it will show what rods and jets to use. A rod change is quick and you'll know what direction to go.

If they are 500 performer changing rod to #6 .067 x .055 it will lean out cruise and power 4% #11 change only jet to .083 and use the factory rods will lean both out 8% and lastly #10 change jet to .083 and rod to .067 x .055 it will lean them out 12%.

On the setting up the two carbs before you put on linkage the backing out of the 2 idle screws to set the carbs the same I was taught after getting them set to set the idle to 2,000 by by turning each idle screw the same number of turns and put your hand over each airhorn to see how even the suction on the carbs are because the difference in the carbs,cylinders and the manifold.You'd be surprised how close you can get them with just a minor turn on idle screws. Poor man's mercury gauge.

Good luck

Second 70, I really appreciate you attempt to help, BUT it's way over my head. I basically am a simple basic person.
In your opinion, changing to progressive should be my first action, and it will reduce the "richness", but probably not enough?
Could not get your link to open for me. Thank You.

It might help a lot or not I don't know for sure.

Sorry that link doesn't work for you try this one.

https://edelbrock-instructions-v1.s3.amazonaws.com/edelbrock/carb-tuning-guide.pdf

If not just go to edelbrook web site click on 500 profomer and the click on tuning guide.

Maybe another member close to you might be able to help you out.

One thing to check is to make sure the metering rods are all the way down at idle, it they are bouncing or not fully depressed, it will throw off your A/F. It's easy to check, just loosen the caps and rotate them enough to see the rod- do one on each carb, all 4 to be through. Then start it up and see. If the springs are too stiff for the idle vacuum of your engine, you will need to replace them. If all 4 are good, then just move on from there. I'd suggest fresh plugs-or sandblast cleaning and re-gapping the old ones and giving it the old Italian tuneup and see how it goes. Remember timing needs to be set right first, then idle speed, then mixtures. If you've got vacuum leaks or the throttle shafts are worn or binding, it all needs to be fixed first. I'm not trying to talk down to you, so if it seems too basic, it's not an insult. I just don't know your background or anything about the car you are working on. If you've got an aggressive cam in it shoot for 1000/1200 rpm at idle, as long as it isn't dripping fuel from the venturis and the mixture screws are able to affect the engine speed. You've got the basic balance taken care of so after blowing the carbon out get the idle mixture set and go from there. It may be worth your time and money to get it on a chassis dyno to get it tuned. HTH, Steve

I have no idea what your mechanic friend is talking about. Carbs are fairly simple devices. They just use small holes to meter fuel and air. If your carbs are too rich then you make the fuel holes smaller and/or the air holes larger. You have idle, cruise, power and acceleration circuit adjustments on those carbs.

Idle should be easy to adjust since you just screw in the adjusters. Cruise and power adjustments require changes to the jets and/or the metering rods.

1:1 throttle adjustment should work okay with those carbs. Maybe not quite as nice as a good progressive setup but 1:1 isn't the reason you are rich.

If all of this is over your head (and obviously too complex for your mechanic friend) then find a local chassis dyno shop where the operator knows Edelbrock carbs. It will take a good Edelbrock guy about 2 hours to chassis dyno tune a dual quad setup and he'll probably charge you $300.

Thanks Steve. You can not get too simple for me, I appreciate the thought. I do a lot of "piddling", and get a great joy of being able to do as much myself as I can. Often as not, my work creates more issues than I solve, but I tackle most.
OK now, to be sure, I can check all 4 at the same time, or check all 4, one at a time, engine at idle?
I'm working on a 48 DeSoto, 1st Gen (1958) Chrysler Hemi, 2 4's. Auto tranny (A727TF), mild cam, small stall converter. Although I go to car shows, I always choose not to be judged. It's a driver, and I enjoy the people, the cars, and maybe couple of cold ones.
I just replaced plug wires (MSD 8.5mm,) (plugs (NKG) . Waiting for new coil (MSD Blaster2).
No moparts members near, very rural area, Chevy people up the ying yang.

I ain't a dual quad expert but I have one on the shelf (iron RB intake/2 4131 AFB's) so I am gonna learn also when the time comes but I cant help thinking that it ain't jetting, that it is one of these: psi/waterlogged float/float linkage hanging up/bad needle & seat/issue with metering springs/minute debris stuck on needle/seat. holler how it turns out.

Not stupid at all.

In fact it's pretty smart. I would verify what you have for a carb and if they are 1403/1404's I would mimic the Edelbrock calibrations as a starting point. One thing I have seen in my Edelbrocks is the floats tend to leak over time, gas gets in them and they sink causing a rich condition. If you pull the float hold it up by your ear, shake it and it rattles you have one of the holey floats.

You are welcome, It's really easy to check, the little cap(s) have a small flat blade screw holding them down. With the engine OFF, crack the screw loose, hold the cap down with a finger, the metering rod/spring will be pushing up on it. Then loosen the screw and rotate the cap just enough so you can see the metering rod, then tighten the screw to hold it down.Push the the metering rod down and let it spring back up, it should psuh down with little pressure and spring right back up. Do this for all 4 metering rods, that way you know none of them are bound up and the springs are't broken or bad. This should take a few minutes to do. Then hook up a vacuum gauge and start it up. Watch the metering rod assemblies, they should be bottomed out. You can push down gently with a screwdriver to verify that they are bottomed out. Again if they are, you are golden. If they are bouncing around, look at the vacuum gauge to see what springs you are going to need. If you don't have it I'd recommend the Carter/Edelbrock carburetors book #SA130 It's got lot's of pictures that are easier to process than a wall of text. Have fun

Skeptic wrote: "One thing to check is to make sure the metering rods are all the way down at idle, it they are bouncing or not fully depressed, it will throw off your A/F."

EXCELLENT suggestion. I had forgot about this. Will make your idle crazy rich if the rods are not seated at idle.

I didn't see this last night when I was typing out my wall of text, very good resource, I'd forgotten about it, Well Done!

Thanks MoParters. You are great, and I appreciate all the good info. Gives me some good suggestions, which I will use. If anything else pops into your minds, please share with me, and others who may be going thru the same issue.

Again, many Thanks.

You're welcome (I know you ain't referring to me!) All we ask is when the time comes to holler with what it ended up being.

Will do.

I am assuming this to be done with engine at aperating temp??

Reporting live from my garage in Southside Virginia...........Preformed your test, all checked OK. Engine off, could easily get them to bottom out, they would spring right back up, Check. Started engine, they bottomed out, and not bouncing, Check.
That was simple easy test, my Carbs passed. Anything else I should check? THANKS

Passed the test Skeptic asked me to preform. Don't know what's next, but will post all new delevopments.

Have you hooked up a vacuum gauge and adjusted the idle mixture screws for highest vacuum at idle?

No, sound and RPMs only. Gonna borrow a vacum gauge tomorrow and check that. I'm going to check the floats?

Now since you checked to make sure the metering rods were down you can see how easy they are to change. Take one out. The size are stamped on them. It's very small and I use a magnifying glass to read.

Also if you're going to check the floats you'll have the top off the carbs and can check the jets also. The primary jets are the 2 in front and secondary are the 2 ones in rear.

A stock primary jet on a 500 would be 386 which is a .086 jet. you just subtract 300 from the number.

I used to run dual 750 cfm (Eddy 1407's, I think was the number) on my Hemi. Yes, they were rich to start but after playing with the metering rods and jetting 4 or 5 times It ran flawlessly, started right up, idled fine and was not too rich on the street. Hemi's like cfm.

Thanks. I have ordered the Edelbrock calubrating kit, is suppose to be here today. I'm going to start by changing the metering rods to same as the Edelbrocks set up on the carbs they sell "specifically" for a 2 4 set up. I will keep every one advised how it wotks. If that doesn't work, I wii go to the jets.

Calibrating the carbs the same as Edelbrock did for dual carb use should have been your starting point when you put them on the engine. I'm not so sure that a calibration kit will have what you need. I'd think you would need to order the jets and metering rods specifically for that conversion. Once you have the carbs converted to the dual quad setup then you can use the calibration kits to tune them to your engine.

Don't forget you need 2 calibration kits 1 for each carb.

After reading through this thread a few questions. Without any O2 how are you determining that the carbs are rich? Soot on the plug? Do you have the correct heat range plug?If so how do you know if it's at idle or wot. Could be caused by weak spark as well. How does the car perform for power? How about idle quality? Are the seats tight in the carb lids? Have you pulled the lids to verify float level? Have you cleaned the idle air bleeds?
Doug

Yes, scote on the plugs. Yes, correct heat range on the plugs, I believe? I'm pretty sure idle and cruise speed, very rarely ever at WOT. Spark, I don't know. New MSD ready run, electronic distributor, new NKG plugs, new MSD wires. New MSD Blaster 2 coil scheduled to be delivered today by UPS. Idle quality, OK, except smell and burns the eyes. Exhaust tips, black as coal. Seats tight, I have not checked. Have not checked floats, but on my "To Do List". Idle air bleeds, details/help please?
Jack

I would start with adjusting the idle mixture screws on all four of them to try and clean up the idle fuel mixture
Start the car up a drive it, if you can, for 15 to 20 minutes to warm it up and then start by adjusting one of the rear carb idle mixture screws in very slowly until you hear a change in the idle RPM., get it to idle as fast as it will Once your done with it one do the other side and then adjust the fronts.
After doing all four go back to the rear and see if you can make it change again for the better or worse, once you got it the way you like it go drive it around again at light part throttle to see if it will clean the plugs up some and the drive it a little harder also
Let us know your results

Sounds like a plan. Hope to get started on all I need to do, 1st thing tomorrow. UPS did not bring all my parts today.

I called Edelbrock Tech yesterday to see if my brilliant idea of changing the jets, spring, and metering rods would work to make my 1401 & 1402 be compatible to the 1801 & 1802? He advised would probably help, but the 1801 & 1802 had been discontined. They have been replaced with 1901 & 1902, and they were completely different, even from the 1801 & 1802?