Uneven fuel distribution

Hi! I have done alot of tuning with my Mopar 493 stroker engine, Edelbrock avs2 800cfm, Edelbrock rpm intale, Edelbrock E-Street heads 84cc, Comp cam xe275hl camshaft(231/237@050), 10,04:1 scr, Fbo distributor set at 18 initial and full manifold vacuum brings it to about 30 at idle, 34 degrees full mechanical advance. The engine running pretty good now with no hesitation or stumble, its just some slight misses at idle. I reading my spark plugs and they all looks good, except cylinder 5, 7 and 6 running richer than the others, is this about the rpm intake(dual plane) or what? The engine do not use any oil or anything like that and i have about 500 miles on it from new rebuild, i did a compression test a mounth ago and i have 200psi on all cylinders cold engine. The blackest one is number 7 and the 2 other rich ones are 5 and 6. The whitest plug is how the other 5 cylinders looks like. So the distribution must be uneven somehow. Last time i checked the plugs it was number 6 that looks black same cylinder 7 does now so it must be about the fuel distribution

What spark plug are you using?
Looks like cold plug based on the thick base.
Off the wall opinion:
Idle too rich,idling cold.and plugs never cleanup
What type of fuel are you using?

Almost any manifold will wet the the floor at low speed and or cold.
Then depending on shape and angles a couple cylinders are very rich cold/idle...
These issues are why stock stuff has high idle on the choke and heated manifolds.

Thank you for your answer! Im running Ngk 6 now, thats one step colder than stock. I have a o2 censor in the drivers side exthaust, the afr gauge is a Aem and by looking at that the engine running a bit rich at idle, betwen 12-13. The thing is the afr reads rich on cruice and wot too, but 5 of the plugs looks really good by reading them and im scared to lean it out more. I have tried to screw in the idle mixture screws at idle but the engine starts to idle bad so i just leave them where i have the highest vacuum. I use same yours 93 octane and in this tank of gas i fill in a boutle of Torco unleaded accelerator to, just for test it.

A lean missfire will make a plug black.

Not an uncommon problem w/dual plane manifolds,
some times the easy fix is to try a one step hotter plug in those cylinders.

Easy to try and can't hurt anything.

Joe

I haven't heard of that, how does that darken the plug?
Not trying to be a smart a a$$, just curious.

Joe

it is just an incomplete burn so no heat & the plug can get dirty

How would you diagnose that condition?

Thanks, Joe

a four gas analyzer,,,,, just set the idle mixture screws for a smoothest idle with new plugs & see how it goes.

A much cheaper solution than a 4 gas analyzer is using a colortune.

Thank you guys for all your answer, im greatful for all ideas. Maybe i should try with one step hotter plugs and set the idle mixture for best idle and see how it looks after some driving.

I have looked at the Gunson colortune and it seems to be a nice product but is not a vacuum gauge good enough for the idle mixture job? And with a 4 bbl carb that feeding 8 cylinders its not so much to do for a single cylinder or a few that running rich. My number 7 spark plug lookes totally black and 5 and 6 are to rich but the rest are good, i just wonder how it can be

If possible, attach some pictures showing a side shot of your plugs so we can see how many threads are getting colored from the heat etc. Ideally, they should have color down to 3 or 4 threads. I have to run a different heat range on several of my cylinders to get the same thread coloring.

I haven't messed with that type of car before, but 12 to 13 A/F ratio is too rich. Can you lean that out a bit? Maybe by dropping the float level a touch, or altering the jetting?

I like to use 14.5 AFR or leaner at idle and part light throttle cruise below 2500 RPM warmed up or hot
How much mechanical, actual, compression ratio do you have?

I have no good picture of that, maybe you can see on this one but it is about 2 threads slighly colored. But by leaning out the carb more going to make the good cylinders running to lean, or have i wrong here?

The compression ratio is 10,04:1, pretty mild cam for the cui, 231/237@050, i have 18 hg/inch of vacuum at idle in park at 900 rpm, snap the throttle the gauge needle drops to 5 and bounces back to 25 and then go back to 18, the needle slightly floating within a half hg at idle. Im thinking that leaning out the carb more makes the 5 good plugs to running lean, like i said there is a rich condition in only 3 cylinders so the distribution must be uneven. Its strange, 5 plugs lookes really good and 3 to rich and the afr shows to rich, how can it be?

On a dual plane, it is sometimes difficult to get all cylinders equal. Runners differ depending on the design.
Some try jet staggering with mixed results DAMHIK.

Some times you just have to go the easy way and mix heat ranges
to get a good plug color, it's not blasphemy.

Joe

I like the looks of that plug
I would lean down the thicker step on the primary metering rods by .002 to .004 and see if it drives good and makes the plugs run cleaner at part throttle cruise or not.
I'm assuming you don't have a lot of choices on where to buy or get Carter or Edllebrock metering rods in Sweden so I hope you can find some like I'm suggesting, don't change the bottom step if you can
If you get a set of rods like I'm talking about drive the car enough to warm it up without getting on it hard , drive it easy and then check the plugs, listen or feel for detonation or pinging, if you hear it or feel it let off the off of the throttle and put the old rods back in it as soon as you can

Thanks, i will try it

Thanks, i will try and see how it goes

Mopar - Your last thread

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2772078/3.html

Did you dig into this carb after my last post ?

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2772078/3.html

Reason I am asking after your last thread

You where just changing metering rods , without changing Jets , and actually went in the wrong direction , very rich

I was just curious if you actually pulled the top off the carb ?



If I would have installed my brand new out of the box AVS2 800 last year

Car probably won’t have ran very good - One of the floats was so far out of adjustment , I don’t know if the needle would have even left the seat


If you did pull the carb apart , what are your float levels , float drop , jetting and metering rods now since your last thread ?

Hi, yes i did, i checked the float level and set it at 7/16 float height and 0,79 inch drop, both main and secondary is 104,
The rods are 65-52. Like i said the engine runs great and 5 plugs lookes really good but 3 plugs are rich and if i lean out the carb more the already 5 good plugs going to run to lean so the distribution must be uneven, my confusing is my Aem wideband, the afr says i go very rich, cruising at 2000-2500 rpm the afr reads between 12-13, at idle around 13 and wot 10-12, thats rich but by reading my plugs some of them are almost white so i wonder what is right here, its so much confusing info about reading spark plugs to, some say look at the base ring for A/F mixture and other says look at the insulator, some say the tip is ignition timing indicator and so on so what should i go after? If i read the insulator of 5 of my spark plugs the mixture is almost lean and the afr says rich like hell so what should you go after. Number 7 is total black as you can see and 5 and 6 also rich by reading insulator and the rest lookes like the go almost lean but afr tell me something total different. I have a stady vacuum at idle of 18 hg/inch, the needle floating little about a half hg/inch but that i think is because of the uneven distribution, when i snap the throttle it drops to 5 and swings back to 25 and after that back to steady 18, if i have a problem in a cylinder the vacuum needle should bouncing around but it doesnt so it must be all good there, this is really confusing and nobody seems to know what you should go after either, plugs, afr or whatever just a whole lot of different info, go by the base cirkel, no go by the insulator, no go by afr and so on. If i go by the afr its running rich like hell and if i go by the insulator reading on the spark plugs it seems like 3 cylinders are getting all the fule and mostly number 7, so i dont really know what to do here.

The question was "how do you diagnose a lean misfire". One answer was to use a 4 gas analyzer. Which is expensive and not very precise. It will tell you if you have a lean misfire, but you won't know which cylinder.

A colortune can be put in each cylinder, you only need one, just move it around, and you will see the lean misfire, it's cheaper and more precise compared to a 4 gas analyzer. Yes, you can also use it to set idle mixture.

The question was "how do you diagnose a lean misfire". One answer was to use a 4 gas analyzer. Which is expensive and not very precise. It will tell you if you have a lean misfire, but you won't know which cylinder.

A colortune can be put in each cylinder, you only need one, just move it around, and you will see the lean misfire, it's cheaper and more precise compared to a 4 gas analyzer. Yes, you can also use it to set idle mixture. [/quote]
Thank you than i understand! The real confuse to me is how afr can show really rich and 5 sparkplug insulators show white, i never get any straight answer anywhere how to properly read spark plug, some say A/F mixture is read by the base circle, some reading on porcelain and so on.

https://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Reading%20Spark%20Plugs.html
Read this! I have always thought looking at the porcelain is the proper way but when reading this thats wrong and maybe can answer why my afr is rich and 5 plugs porcelain still white. But 3 plugs still show super rich so i dont know how to do, maybe another intake manifold is the answer of this uneven fuel distribution i dont know

After another test drive it was number 6 that was totaly black instead of number 7 and still 3 fat cylinders so its not just a single one of them thats running fat so i belive the problem is and i have always belive it that it is the distribution of fuel in this intake that is uneven, maybe its just so that the dual rpm intake not working properly for my combo. Im going to try a street dominator intake, i know the single plane are better for distribution and are more forgiving in the low end on a stroker engine, if it is better for even distribution and i maybe have to give up a few lbs in the bottom end so let it be so, the bottom end is huge on this engine and im not a race driver so i belive im not even notice the different, the engine have more power than i ever use, i want the distribution even and the engine feeling well.

https://www.trifive.com/forums/showthread.php?t=60876

Here is one persons experience with a dual plane Edelbrock air gap intake, there is some experts that have to scratches their heads a bit.

Doubtful it's an issue with the Air Gap design, many people run them without this issue. Which is not to say your specific manifold doesn't have an issue.

Years ago I ran into an engine that had the two outer plugs on one side and the two inner plugs on the other side all carbon fouled. All four plugs were fed by the same half of a QJ. The carb was in need of a rebuild.

Look at commonality issues is my suggestion. You realize the three cylinders you are having issues with follow each other in the firing order? Did you look at that?

I had two bad plug wires on my similar build running E Street Heads 75cc Angled Plug
They where carbon fouled on the terminal end where it clicks on the Spark Plugs

Also thats why i asked if he opened up the carb and checked everything and he said he did

In his initial post he mentions Slight Misses At Idle ???

As in ??? Fuel or Ignition related

Also are you running any type of carb spacer or 4-hole gasket with that intake manifold ???

all intake manifolds have distribution issues. some worth dealing with, others not. the cut out in the divider is supposed to help with that. for my 2 cents i'd give a hard look at the carbs driver side secondary bore. long shot but something could be going on there.

Nobody seems to want to blame the air gap intake, i have google alot in different forums the last day and not only Mopar forums and many people seems to have uneven distribution problems with it, one example is that person in the link i post above, my engine runs really good actually and for sure i havent even noticed the uneven distribution if i not have started reading the plugs, its only a slight miss at idle nothing big at all, almost not noticed on the vacuum gauge but i not want any cylinder going lean. Its alot more people running into this issue so there must be some ground in it, this man in the link above also have the engine in a dyno and a few enginebuilders scratches their head around him so its worth reading. One other thing i not have thinking of until now is that this carb i have is a avs2, so its annular boosters in the primary ports witch atomize fuel little same efi and what i have heard many people say that efi works best with a single plane manifold because of the atomized fuel. Before this carb on the same engine i have a regular avs 800 carb and im not noticed this problem with that one and im same always reading plugs with that carb to, i only switch to the avs2 because of all good i hear about it but in this case it become a problem instead, just a thought.One more thing is that the afr readings is very erratic to, Thats why i think maybe a street fominator intake would sute this combo better

try the regular avs for a test. i'd be curious as to how that works. I have a friend with the regular 800avs on a 427 chevy, edelbrock intake, and it performs quite well. I tune the engine and had to step the jetting down on the primary side to clean the plugs up. i'd still look at the driver side secondary system. with a normal fuel distribution issue #5 shouldn't have a real problem, UNLESS something big was going on at that back corner and fuel was bleeding across the manifold divider.

I drive with the regular one until 100 miles ago so this avs2 is really new for me. The regular one i leaned out one step and after that it runs really good, a little on the rich side but much more even on all cylinders and no idle miss. I switch to the avs2 carb same size and have drive it for about 400 miles and tuning up and down but not get the distribution even, i have not think about it until now, i just think the carb need to be tuned right but it must be something with this annular bosters atomizing the fuel and the combo with the dual air gap. I have asked Edelbrock about it but they not want to answer my question they only want to sell Fi tech to me. From what i have reading in many forums, people have get distribution more even with a 1" open spacer or a single plane and that leads me again to street dominator if i should continue with this carb and on a big stroker i not think i give up so much low end, this combo has more power in the bottom than i ever use anyway.

Read the two quotes

No one want to blame the intake

A different style carb didn't show this issue on this intake.

New carb shows the issue.

Maybe your problem is the new carb, tune/fix it or put the old carb back on.

Or you can spend more money on another intake, your choice.

What am I missing here

In your initial post your running a Edelbrock RPM INTAKE

Not a Air Gap Intake

How did we even start talking about Air Gap Intake which is for a small block ???

The RPM has a divider but is cut out for fuel distribution ,that’s why I mentioned if you where running any type of spacer under the carb


Anyways


Also this is the first time we are hearing of you running a Regular Edelbrock 800 and it sounds like you honestly had zero issues with that carb , THEN you installed the AVS2 800 correct and all your issues started ??

That’s why I kept asking if you opened up the carb and checked everything

Well it sounds pretty simple to me

X10

I send Edelbrock a question earlier and describe the whole situation and in the first they only suggest a fi tech but i push the question further and i get one more answer just a few minutes ago and they answer that the fuel distribution is more even in a single plame manifold and that the avs2 because of the fuel atomize and a single plane might be a better choise for my combo and that a bigger volyme engine is much more forgiving with a single plane in street use. That answer and my exprience with the regular avs and everything i have read about it makes me believe that a street dominator maybe not are a step in the wrong direction, like i said before im not the only one with the same issue. I have a good steet dominator intake in my garage from another 440 so i give it a try. Also i have going through this carb more than once and its nothing wrong with it.

I run that same AVS2 800 on my little 432 with a dual plane intake and I can light the tires off idle from Green Bay to Chicago


However I had to reset the floats brand new out of the box like I mentioned

generally annular boosters seem to work better on engines with lower vacuum, or engines that may be a little over carbed. 18"hg at idle is better than the stock engines were. I still think i'd take the carb apart for inspection. the avs2 probably has no practical advantage with your engine combo. edelbrocks FI suggestion is something to get you to spend more money. run the regular 800avs and just enjoy the car.

Its nothing wrong like that, the engine runs great, from still standing i put in second gear in the727 automatic, 2400 stall converter, 3:55 in the rear and a heavy Chrysler 300 1964 it throws the car away like a bullit with no hesitation what so ever anywhere, the power is huge. It is just the uneven distribution that disturbs me and if another intake can fix that its maybe good. I have a friend that a have driven the dominator intake on his 440hp for years and it runs like s charm on the street, i just thought that the air gap intake should be even better when i building my engine, but thats maybe wrong, i dont know until i try it.

Years ago when we used the 4 gas analyzer at the dealer for emission readings it made it easy to see a lean misfire. The HC will shoot high since its like raw fuel and of course with the misfire you get raw fuel that don't burn since it was to lean to burn when the plug fired. To try and pick out the cyl we would short the plug wire out per cyl to see which one did not make much change in the high HC reading. Today the temp gun on the exh manifold or header is nice also. Also a lean misfire wont usually leave the plug black and fluffy like some rich conditions do as it will usually leave the plug wet since what fuel was in there did not ignite and raw fuel gets on the plug that has not burned any. Ron