Tom 400 CFI

You can find out about my engine combo here:

https://www.thirdgen.org/techbb2/sho...hreadid=250000

If you 'll notice in my sig, I live in Park City, UT, which is at 7000' eleavtion.

This is the most un-responsive, stubborn, POS carb I've ever worked on...and I've probably worked on more carbs than most people on here; Holley's, Q-jets, Mikuni's, Kiehin's, Edelcrap's, Zenith's, Stromberg's, Schebler, Motocraft's, Tillotson, Mercury, Weber, Solex, Walbro, Ping... I pretty much think I understand carb theory and I never have had a problem getting one of the above to work, and work WELL... until this focking pile. It's a 1411, and it's almost brand new. It is really about 10 years old, but it has sat (on this car) for the last 2 of those years, un-used. Prior to that, it was run several HUNDRED miles over the previous 8 years. Not much. Hence the "almost brand new". I bought the car in MA (sea level) and it ran fine there. Here though, at high elevation, it has a WICKED annoying stumble on tip in. The focked up thing about it, is that it will do the stumble at the same spot in the throttle, under any and all conditions! I can be starting out from an intersection, and it will stumble...stall if I don't "play" with the throttle and clutch. I can be cruising on the highway, 2k RPM, let of to coast for a moment, and then EASE back on the throttle, and right when I get to that point, ANNOYING HESITATION! I also have a POS Edelbrock A/F ratio meter and when this stumble occurs, all the lights go out (indicating a LEAN mixture). Now, when I am starting from an intersection, it stumbles (jerks the car annoyingly), and then lurches forward with no issues after that. When CRUISING, I can actually hit that "spot" on the throttle where it does it (only while advancing the throttle), hold it right there and it will stumble, and stumble, and stumble, almost indefinitely if I hit JUST the right spot, all the while my A/F ratio indicator is dark.

I have:
* Adjusted tha carb according to the book for this elevation. This made ZERO difference in not only the stumble but in general power, drivability fuel economy, and the A/F ratio readings. How could that be???
* Tried every pump shot setting including DISCONNECTING the pump altogether. This made....ZERO DIFFERENCE!!! Amazing.
* Raised the float level in an attempt to get the Main circuit to "pick up" sooner/quicker. Made...zero difference.
* Changed the metering rod, springs in both directions of "spec" .
Made...zero difference.

When I say "zero difference" Don't read "zero improvement" here. I really mean there has been absolutely ZERO change one way or the other, in the performance of this carburetor since I moved here, dispite a plethora of changes! Hence my opinion that it is the most un-tunable, stubborn and insensetive (to vacuum signal) carb I've have ever witnessed! A total piece of sh:t. Any comments are VERY welcome, but it my mind, a Holley is the fix (w/requisite tuning), and the sh:t-pile Edeljunk is going to end up about 1/2" thick, under the bucket or our Caterpillar loader here at work. Edel should stick to intakes, and stay out of farting around w/40 year old, Chrysler/Carter carb junk.

Edit: At 1000 RPM idle, the engine pulls 10" of vacuum here at 7000'. The stumble doesn't seem to be vacuum related or engine speed related. It just seems to not be able to transfer from the idle circuit onto the main. I guess that's too much to ask of this hunk.

Edit II: The accelerator pump DOES work. It just doesn't make any difference.

Edit III: I will give this carb credit for one thing. It actually DOES respond to idle screw changes! WOW, a circuit that actually RESPONDS to something!! Amazing! The idle screws DO actually do something.

92MaroRS

if it sat for 2 years without being ran on a regular basis something on the inside is prolly gummed up after sitting so long. tear it all the way down and clean everything througly and see what happens.

Tom 400 CFI

Done that.

Was clean as a whistle.

92MaroRS

when you tore it down what did you do exactly?

Tom 400 CFI

Well just to make SURE, I have it apart (again) right now. At the moment, it is taking a very hot shower in our aquious parts cleaner here at work. This seems redundant to me, as I've already blown through every passage possible w/both air and brake/parts cleaner.

I have the carb as disassembled as it can possibly be. The boosters are out...everything. Every passage way seems to be clear and free flowing. It's so clean it looks like it just came out of the machine shop (from when they bored all of the passages into the casting at the Weber factory). It's clean, and it was before I even started. It literally looks brand spanking new.

PS, I love the "counter weight" vacuum secondary flapper things. Reminds me of one of those draw bridges with the big counter weight. What a goory design. I wonder if those stupid things bounce open and closed when you hit bumps in the road.

-Tom

92MaroRS

nope. it would take one hell of a bounce atleast.


just out of curiosity what is your idel set at?

Tom 400 CFI

750 RPM.

Idle mixture screws are 1.5 turns out.

Just got it back together. I'll drive it home right now and report back.

-Tom

Tom 400 CFI

Well I just got home from working on the car at my work/the shop. It's about 5 miles of secondary roads w/stoplights, and then about 5 miles in I-80. So I got to run it in all modes. As far as the hesitation/stunble is concerned...ZERO DIFFERENCE! Why am I not surprized? lol.

One thing I will say that is better though, is this: While re-assembling the carb, I left out the REtarded "draw-bridge" flapper junk for the secondaries, and I'm happy to say that the car does have much better punch and power when going to and at WOT, above 2500 RPM. Way better. I would say that this is a mod that every Edelcrap owner shoudl try. It's so quick and easy, if it doesn't work for their combo, slap the old draw bridge back on there.

KrisW

iTrader: (5)

Just my 2 cents.........
I've had a lot of Afb's on old buick engines. When I was in the service, I was in Socal. I would drive back to Colorado with a buddy and if we stayed longer than 3 days I would have to re-jet the carb down (lean) in order to live with it.
Just thought I'd throw that out there.
Good Luck!

92MaroRS

when you say you adj. it to the specs in the edelbrock book did you just take it to what it said for elevation? or did you go further than that. if not id say trying going a jet or two larger as it sounds like the problem i had with mine and i was a wee bit lean. two jet sizes up and it made a world of difference.

Tom 400 CFI

When I got the car to UT, I figured I would have to most defitely re-jet the carb. When you go from low elevation to high, your engine runs progressively richer, the higher you go. So when I got here it should have been WAY RICH.

According to my A/F meter, AND my gas milage through Wyoming and into UT, it was rich.

It didn't hesitate/stumble at sea level (MA), so the problem, at least when I first arrived here, was NOT that it's too lean. Follow me?

When I did make the changes for elevation, I did follow the specs in the book to a "T". This should have leaned out the mixture. This was to be a starting point. The problem here is that those changes made ZERO DIFFERENCE. If the stumble was because it was too rich when I first got here, rejetting should have cured it...or atleast made some noticable improvement. If the stumble is due to a lean condition now, then it should have been non-existent when I first got here, yet should have stumbled when back in MA, which it didn't.

Usually, you make a change like that, then make little changes in both directions to see what the engine likes and move int eh best direction, until you see and "peak" and go back to that point. Just for yuk-yuks, I have tried going up and down in jet sizes and changing the metering rod springs in both directions just to see if the engine liked one side or the other of spec. But with all these changes there is ZERO DIFFERENCE, so I have no idea what the engine wants from this carb.

In two strokes, when you get and engine that has a driveability issue that seems carb related, and you just can't tune the problem out of it, (or maybe you do but then it comes back, and you tune it out and it comes back again, etc.), it is a sure sign of an air leak or critically low compression. Every time. You fix the air leak (crank seal, etc), or get the compression back up above ~80 PSI cranking, and you get stability, consistency, and tunability back. This engine has no vacuum leaks. I have checked thoroughly. It also has sufficient compression. Other than the idle circuits, the carb just plain doesn't respond to squat.

I think the problem is that there just isn't enough draw at the discharge nozzle to pull the fuel out of the main circuit. I think this is due to my engine combo, and the sh:tty design of the carb. I think my stumble occurs EXACTLY at the point where fuel delivery from the idle circuit falls off (as the throttle plate is getting to far open) but there is still no flow through the Main. The carb needs an "off idle circuit" like a Q-jet has, IMO. I don't think this problem is fixable with this carb.

Edit I: I said above that there are no vacuum leaks. I have to be completely honest and admit that there is a small vacuum leak. it is where the throttle plate shaft passes through the cheap-o carb casting and has some slop (secondary side only). Even thought the carb has almost NO USE, this shaft does have some slop, and there is a little leak there, as verified during idle w/a little brake/parts cleaner. Cheap-cheap!

92MaroRS

id try going even farther rich. as it sounds like a lean condition. with carbs as you should know as yousaid you have worked on alot, that they dont always act like they should. i have a 1406 on my truck and i love the carb. easy to work on andrun like a champ. every one i know with an edelbrock just loves em.

ljnowell

I wouldnt be blaming it on the carb, that much is for sure. That style carb has worked just fine for a long time.

92MaroRS

thats what i was thinking. maybe check the dist.

Tom 400 CFI

Well then lets hear some suggestions! Good Gaud. O.K. so that style carb has been around for a long time. So has that style block, heads, dist., intake, radiator, and hubcaps too. But dispite that fact, that fact alone isn't helpng me get this CARBURETOR to deliver the proper A/F ratio to the engine, at about 1/8 throttle.

'92Maro, You DID offer a real suggestion, and I appreciate that, but I'll ask you this; how much should I richen it? Back to stock sea level? (about 10% richer than now) Or even richer than the sea level jetting, even though it didn't do it at sea level, where should have been leaner.

Tell me how rich you think I should go, and I'll do it tonight after work. I have a PILE of jets, so just offer up a suggested "range" for me to try, and I WILL try it. I put money on that it doesn't make a change, but I'll try it for sure. What do you think?

P.S. The Dist is fine. It's as new as the carb, and it functions well, IMO.

-Tom

92MaroRS

well when i had this problem when i finally got my truck together i had to go 3 stages richer. if you have a pile just go like 3 or 4 and if the problem goes away lean it back to where it is present and then go one step richer. if after 4 stages richer it doesnt go away try going even more if after say 7 stages it isnt gone then i would say try something else. any poping back through the carb? does it do it out of gear? out of curiosity what jets and rods do you have in it?

Tom 400 CFI

Alright then. I'll start off 4 sizes richer and go from there, and report back both the changes I made, and what the results were.

Right now, there is no, I mean zero, popping through the carb. I kknow what your after here, lean backfire. But it doesn't do it. That's why I had thoguht maybe it was getting too much pump shot and flooding for a second, and I tried fiddling with the accelerator linkage, all the way to disconnecting it (as I mentioned above) which resulted in no chage at all.

When you rev it in neutral, there is a stumble, though it gets through it pretty quick.

If it's in 6th gear, and i'm at 2000 RPM on flat ground, I can step on the throttle SO, SO slowly from coasting until I get to that point at about 1/8 throttle and it will stumble, and stumble, and stumble, and (A/F/ratio lights completely off) stumble, on and on and on, until I press the throttle just an RCH more, and then bam! all the LED's on the A/F/ ratio meter light up and the car goes. This pretty much eliminates the Accelerator pump as the cause.

I'll adjust and report back.

92MaroRS

if going richer does not do anything for it try doing the same going leaner. also maybe try a weaker spring. could be that its too strong and dumping in too much fuel to early. i assume it does this cold and warm right? also have you put a vac. gauge on it to see what it does pull for vacume?

Tom 400 CFI

I've already tried the spring for sea level (was in it when I got here) the recomended spring for here, the spring stiffer than that, and I'm currently running the softest (3") spring. None of the springs made any difference what-so-ever.

I have had a vacuum gauge on it plenty. When fully warmed up it pulls about 10" vacuum at 1000 RPM.

It does it exactly the same, warm, hot, and cold. See? The darn thing doesn't even respond to temp changes!

Good point about the springs, but as I just described, I've pretty much covered that one.

Am I answering your questions clearly?

-Tom

ljnowell

You know, if you're that biased why dont you just get a different carb? Personally, If the thing ran fine before you got there, needed to be adjusted due to elevation, and you made the changes, I see only one link inbetween. You. Maybe you didnt quite get everything right. But, honestly, I have never seen anyone bitch so much and have such a bad attitude to other people over a carb. Go buy a holley and tune it for a while. Maybe you will have better luck.

Tom 400 CFI

Der. Like I can't read a book, change 4 jets, two springs and two rods. Give me a phucking break dude.






I'm working on it. You can rest, assured that there WILL be a Holley on there, but I keep missing/getting out bid on ebay. Just give me a little time. IN THE MEAN TIME this is so unbelieveably aggrivating to drive, I'm trying to fix/patch it.

At least '92maro is thinking and helping out. I've yet to see you offer any form of constructive advise. Can you offer ANY explaination as to why this carb is so un-responsive to changes? OR any direction I might try? (that I haven't already)

ljnowell

To tell you the truth, the biggest problem that I have seen with an edelbrock (and yes, I own one now, many in the past) is that they like to gum up. Sometimes an edelbrock will run like crap, and all that is needed is a good cleaning. Yours seems to be another problem. If you have done everything that you have, and it has had no response, not even a negative one, there is some overruling factor involved. There is in fact something wrong with it, but not being able to see it, and play with it makes it hard to diagnose, especially when you seem to have covered your bases. Also, the reason I get pissed is that people make posts about this ancient POS, that shouldnt be made, that edelbrock shouldnt make carbs, that it is useless. They are great carbs, especially in the hands of someone that really knows them. The point is, yours is junk, not all of them.

92MaroRS

what are your current jets and rods? what are you running for timing? how do your spark plugs look? i know it might seem like a stupid question but how did you adjust your idle?

Tom 400 CFI

ljnowell, thank you for a well thought out post. I agree. Mine in particular does have some issue, and I should not have generalized so broadly. Sorry for that. I CAN assure you that my carb is as clean as any used carb has ever been. I'll tak pics and pist them if need be. I hear you about gumming up, but this thing is clean.

'92Maro, I don't know the needle and jet sizes at the moment. I'll check and post back when I do the jet changes.

For the idle, I adjusted the screws to obtain max RPM. First one, then the other, then the first, then the second again and so on, until I'm sure I have obtained the best Idle possible. Then I back off the idle stop to obtian desired Idle RPM and then hit the mixture screws again to obtain MAX RPM again, then made a final idle stop adjustment (very minor). The Edelbrock manual states to do this, but then they go on to say that you should turn the idle screws IN (leaner) some amount I can't remember how much but I didn't do that. When I find the best setting, and try to lean it out at all, the idle gets SO ragged, so fast, it just doesn't agree w/me. The "sweet spot" on the idle screws is very obvious.

The plugs are black.

I'm going to leave work now, and go Mtn Biking for a couple hours. I'll change jets, read the needles, and type back later. Thanks for responding.

-Tom

92MaroRS

migh be worth it to stop and get a NEW plug for a good read. only need one and put it in and then that would giv eyou a good idea as to what its doing. dont be surprised when you take it apart that you cant read the jets or rods. i would still go rich and see what it does.

Tom 400 CFI

Just got home from work. Here are the specs as the sit right now:
Mains: .101 #1429
2ndaries: .098 #1427
Rod's: .075 x .047
Springs: Blue (3")
Float Ht: 3/8"

Idle Screws; 1.5 turns out
Idle vacuum: 10 "
Idle speed: 750 RPM

That's about it I think.

-Tom

Edit: '92Maro, you're right, the numbers on the rods and jet's are wicked hard to read. You need a magnifying glass.

92MaroRS

how warm does teh motor run?


this seems like a lean condition.


here is what i would do.

Try the 8" spring.

if that doesnt fix it stick with it.

keep with the rod you have.

go to a .110 jet in the primaries if you have it.

leave the secondaries alone for now. if this doesnt do anything for the problem or makes it worse we know we are going int he wrong direction which at that point try a .098 jet. if problem gets better but doesnt go away try going another step richer until it goes away.

F-BIRD'88

"The plugs are black" Why?

you'll never get good throttle response with fouled plugs. Sounds like some other roblem like plugs or ignition. Because the carb never changes reguardless of your tuning changes. Survey says: its not the carb.
Can yu borrow another carb and try it?

Got another distributor?

As a note: the carb seems to improve when you take out the secondary velocity valve because at high elevation the air is thiner. ( it weights less) therefore the air valve seems heavier ( it is , relative to the thin(er) air acting against it). Causing the valve to open too slow or late(er) than it did at sea level.
The solution is to lighten the counter weights on the air valve. Carter used to sell various air valves of different weights for the AFB.

This won't cure your off idle tip in problem but.....

92MaroRS

from reading ive done it depends on what part of the plug is black. if the porcilin is black that doesnt mean much but if the fueling ring is all black then you are rich. honestly depending on how long the plugs have been in there you cant get a good read unless you get a new plug.

F-BIRD'88

Sorry, but if the porcilin is black, the plug is carbon fouled. Time for new ones.

Carbon conducts electricity and short circuits the plug causing missfires. Especially while accelerating.

KrisW

iTrader: (5)

especially in 6th gear overdrive -- that's the biggest load lag you'll get.

92MaroRS

cant hurt to replace them.

KrisW

iTrader: (5)

Sounds like an ignition problem anyway--MISFIRE UNDER LOAD--common enough. I love my carter AFBs and Edelbrocks, the only time they go away is when fuel injection replaces them!!

Tom 400 CFI

Guys, thanks for all the replies, but let's take it easy on the ignition system. That isn't the problem. Most of the time when an ignition system fails it is during the highest cylinder presure. This would be at WOT. Also high RPM is a good time for ignition to break down. This does neither. I can run from 1500 RPM to 7000 RPM at WOT and the thing won't miss a beat. Pulls nice and hard too. At no time during this type exercise, does it missfire. Ignition system is fine.

I will replace the plugs just to eliminate that.

This propblem occurs AT THE SAME SPOT in the throttle range every time.

And I gave the 6th gear example to show that it isn't the accelerator pump. It also does it in first (the most annoying because you're trying to start out from and interesection), it does it in second, third, fourth, fifth, and sixth. Any gear. It is totally dependant on throttle position.

I'll say it again. I thin there is a spot between the idle circuit and the Main that this carb won't deliver fuel. I think as I ope the throttle, the velocity dies off near teh idle port, and the idle system shuts down, but at this point, ther eis not yet any fuel flow out of the main nozzle. That's my opinion, and I want to figure out how "patch" up this spot. I think '92Maro is onto something w the going richer idea. Even though it make no sense relative to my elevation, it does make sense seeing as (IMO) the carb is unable to ddraw off the main system early enough.

-Tom

P.S. I didn't change any jets tonight. My Mtn bike ride took much longer than anticipated, as I got a flat, and my spare tube had a hole in it. Grrr. That made for a long walk back the the truck in the dark

KrisW

iTrader: (5)

Just another 2 cents, I Know you covered this but I was reading through my Edelbrock carb book and it says that Idle to off idle to part throttle is more affected by the idle screws than anything else. Did you take out the screws to make sure some little gremlin dirt plug isn't hiding? Not being redundant on purpose. Also the 2nd idle air bleed passage which goes into the top casting piece of the carb.

forums_suck

i hope i didnt miss this point but did you phone edebrock techs at all?

CaysE

Wow, what a read... here's a thought:

Have you tried accelerating the throttle on the carb itself instead of from the gas pedal? I'm thinking if the carb adjustments don't affect the problem, and the ignition is fine, it must be something mechanical, like a throttle linkage slipping or catching on something.

ljnowell

Did you ever figure this demon out?

AnotherfastIROC

I heard a few other people say ignition and although you disagree I think It may be as well I know with my Oldsmobiles the ignition timing is very touchy if it off by 1-2 degrees base it will flat spot in the same way 1/8 throttle I tore the carb apart about 700 times trying to fix it and nothing. I eventually found the timing was off, and to bot the timing advance was mis adjusted. Now I'm not gonna say 100% that thats your problem but hey, why not check before the next carb teardown?? Just a thought. I hope you get it running good luck

Tom 400 CFI

Been really busy this week, and I've done a couple things, but didn't really "get into it" until tonight.
SO, here's where I'm at.

The plug reading I had from before was not good, because it was a mix of driving, then idling, the "just pulling a plug". I thought it had some validity, because the useless A/F ratio indicator always says rich. I bought new plugs, ran up Parley's canyon, (3 miles of 6%) in 6th gear, 2000 RPM, cut it of clean at the top and pulled plugs. Even thought the worthless Edelbrock A/F ratio meter was reading 10:1 all the way up the hill, the plugs were chalk white! So '92Maro was on the right track.

First I put in the stiffest springs available, the silver (8"). That made no difference whatsoever.

Tonight I changed the main jets. That seems to have reduced the problem when "rolling back onto" the throttle while cruising, but it still stubbles embarrassingly and annoyingly leaving any and all interesections.

When I'm crusing at 80 mph, 2000 RPM, I am betwee 6" and 9" of vacuum, so I think I need to go back to the Orange (5") spring.
Starting out from an intersection at a"normal rate" with "normal RPM", the vacuum drops to about 3".

Here's where I'm at now:

Main-------------.110
Recomended--.104
Needle----------#1450
Spring-----------Silver(8")
Recomended---Orange (5")
Float Height----3/8"
Recomended---7/16" (so the fuel level in the bowl is 1/16" higher.)


I guess I'll just keep going richer on the primary. (?) The .110 main, that's what Edelbrock recomends for sea level operation.

Other beef's I have with this thing;
*Difference between fuel height and nozzle height...Too much, IMO
*When I took the lid off tonight, there were air bubbles coming out of the primary and secondary jets. Boiling. The car runs at 160*. (?)
*Flapper door "vacuum secondary" design. No good.
*Massive fuel slosh (loose half the engine) during hard cornering. Isn't this a "performance" carb?
*Hard starting when warm. From the boiling?

So I guess I'm making progresss. I'll keep goign richer, and let you all know what the results were. Anyone want a free/useless Edelbrock A/F ratio meter? It has cool lights that light up (all the time )

Tom 400 CFI

Well, I went to my first auto X of the season today.

How in the WORLD do you get this carb so stop drowning cylinders on corners???

Not only is this extremely EMBARRASSING, that my gorgeous Camaro gets out on course and runs like garbage, but it's KILLING MY TIMES!!

When I exit the corners I don't know if I should be expecting the power of a TFS headed 350....or the bog of an Iron Duke!

I seriously hate this carb w/a passion.

Low C1500

Do you have any way to tell your exhaust air to fuel reading. I mean do you use an O2 sensor to tune with?

Me I use a stock one wire O2 sensor, and a digital voltmeter. This tells me really fast what I've got to change on my edelbrock 750.

Apeiron

Maybe try the #1465 spring-loaded "off-road" needles and seats, and get your float level as low as you possibly can.

Tom 400 CFI

No I don't. The car came w/the Edelbrock A/F ratio meter installed where the ALDL used to be. It appears to be about as effective as the carb it's supposed to be monitoring. So I read plugs.

The issue isn't the A/F ratio (anymore), it's the A/F ratio when I'm negotiating aggressive corners. BOOOOOOOOOOOGGGGG!

Apeiron, I can try the off road needles, but how is that going to help bowl slosh?

On another note, I have a 4150 I'd like to put on to finally eliminate this major hassle. There are two problems however.
1. there is no port on the Holley for the vacuum brake fitting.
2. the only place on the RPM intake I have seen that is drilled and pipe threaded is immediately behind the carb. W/anything other than a allen/hex piple plug in there, the rear float bowl on the Holley hits what ever is there. So, no room for vacuum port there. How do guys running a Holley/RPM combo get vacuum for brakes and HVAC?

Thanks.

Apeiron

I don't know, I'm reaching here.

There's a low-profile 90 degree hose barb you can get to put in there that might work, you might need a thick gasket or a spacer for enough clearance though. If you were going to run a spacer though, you could just drill and tap a 1/4" NPT hole in the back and stick some sort of fitting into it.

Tom 400 CFI

O.K. Thanks. i'll check on the 90* barb, and then go from there. Drilling and tapping is what I figured I'd have to do next.

-Tom

contact

I know this is an old thread, but,

Tom,
are you sure that all the small air bleeds on the
topside of the carb are open?,

are you sure that the {primary side} 'transfer' slots
are, open and working?, these slots are above the idle holes.

You seem to be throwing fuel at the problem, which
does not help, causes problems elsewhere.

You might try some thing like...
wire the secondaries closed, either with the
air valve, or any other means.
then, put in lighter springs,

and try to isolate the problem by, think 'lean',
which will make the problem obvious.

There is no reason for this.
are both primaries delivering fuel?

consider taking the spings out, with the secondaries
wired shut, what happens?
sometimes, makng the problem worse, is helpful
for understanding
I assume the EGR is disconnected.

saoco383

If you need more fuel after trying almost every adjustment there- is it seems to me that a JET EXTENSION is what you need to keep them jets submerged in fuel at all times no matter which way you go, because you said something about a hill and 1/8 throtle from a stop, yeap jet extension.