Tuning an Edelbrock?

88 Fox GT · Mar 4, 2004

I have a 600cfm Edelbrock 4v carburetor and need some help tuning it. I have a sputtering problem at WOT so I am going to try to either lean or richen the secondary circuit. The book I have says that the main jets meter ther fuel on the secondary high speed circuit. There are no metering rods involved. Does anyone know about tuning Edelbrocks? I need some help. Thanks.

jikelly · Mar 4, 2004

Yep I've done a lot of tunning on my carter carb and it is the same design. In order to adjust the amount of fuel going into the secondary circuit you will have to remove the top of the carb and replace the secondary jets located at the rear with a different size. Hopefully you have a strip kit that comes with many different sized jets, and metering rods. If not you should get one.

To check to see whether I had a rich or lean condition I would run the engine at WOT and while holding down the gas just shut the engine off. After that I'd read the spark plugs. Light colored spark plug electrode lean, Dark colored rich. Then I would just try different sizes till I got it right. Actually the best way I found to tune the carb was to make a single adjustment (change either the primary jets, secondary jets or meetering rods) and then time a 0 to 60 run. When I found the best time I would move on to the next circuit. The book you have should tell you how the metering rods and primary jets work toogether to meter the amount of fuel in the primary circuit. (I think it talks about the total opening, orafice size or diameter.) I suggest making a chart with the resulting sizes from the different combinations and then write their coresponding 0 to 60 time next to them.

Another thing that has a massive affect on the fuel mixture is the choke setting. I simply would make adjustments as a drove around town until I got the desired response at part and WOT.

Jonstantine · Mar 5, 2004

is this sputtering just at low end, or all the way through?
is it a bog? or does the sputter come after youve had it floored for a bit?

exactly what do you need help with?
do you know how to pull the airhorn right?
cause the jets are underneath it..
if not, its 8 screws on top and 3 pins; becareful with the pins.. i lost a bunch and had to find a hardware store with some
pins: acclerator pump on the front right
one on the left and the other on the right (sides)

by far the easiest change to make is the metering rods
metering rods actually change what the carb thinks the jet size is

have you messed with the carb before, or is it completely stock?

also to do adjustments, you will need a kit that has extra jets and rods if you dont already have it

answer these questions and it will be much easier to help you

88 Fox GT · Mar 5, 2004

Jonstantine said:
is this sputtering just at low end, or all the way through?
is it a bog? or does the sputter come after youve had it floored for a bit?

exactly what do you need help with?
do you know how to pull the airhorn right?
cause the jets are underneath it..
if not, its 8 screws on top and 3 pins; becareful with the pins.. i lost a bunch and had to find a hardware store with some
pins: acclerator pump on the front right
one on the left and the other on the right (sides)

by far the easiest change to make is the metering rods
metering rods actually change what the carb thinks the jet size is

have you messed with the carb before, or is it completely stock?

also to do adjustments, you will need a kit that has extra jets and rods if you dont already have it

answer these questions and it will be much easier to help you

It doesn't bog, it just sputters at WOT. Right when the secondaries open up it will start to sputter and it doesn't come out of it no matter how long I hold it going down the road.

I have some experience with carburetors and how they work. Yes, I realize that the metering rods restrict the amount of fuel depending on how large they are or how far they are away from the main jets. That's why I am confused as to why the book says the secondary high speed circuit doesn't use the metering rods. But would changing the metering rods fix my problem? Because that's a very simple thing to do.

speedy66 · Mar 5, 2004

change your metering rod and spring.. go one size larger, and go to the silver spring.. try that..

jikelly · Mar 5, 2004

Changing the metering rod might help. The springs under the metering rods adjusts when the rods are allowed to step up the amount of fuel moving through the primary jets. If you have a stumble or bog when you are under light aceleration then you need to change the springs otherwise you will simply be prematurly riching your mixture. I don't think changing the springs will help with your current problem. Please keep in mind that the primary and secondary fuel metering circuits are separate.

Your engine may be running at the proper air fuel ratio on the primaries but may be leaning out when the secondaries open due to too a small secondary jet size. If this is the case and you up the size on the metering rods (actually a smaller size rod lets more fuel through) you may solve your lean problem when the secondaries open but you will create a richer primary circuit and probably reduce drivability at part throttle.

It took me a very long time to optimize the metering rod and jet sizes on my carb. I suggest focusing on one circuit (primary or secondary) at a time. I constructed an air fuel meter to help me see exactly how changes I make are affecting my air/fuel ratio. It was not difficult although it wasn't as easy as the instructions made it out to be.

88 Fox GT · Mar 5, 2004

It revs up and takes off nice and smooth at any throttle position. But if I floor it at ANY speed and open the secondaries it sputters like hell. So you think changing the metering rods will help? How much does a kit usually cost? Thanks.

speedy66 · Mar 6, 2004

60 something

Jonstantine · Mar 6, 2004

my kit was about 50ish - summit has em

Your engine may be running at the proper air fuel ratio on the primaries but may be leaning out when the secondaries open due to too a small secondary jet size. If this is the case and you up the size on the metering rods (actually a smaller size rod lets more fuel through) you may solve your lean problem when the secondaries open but you will create a richer primary circuit and probably reduce drivability at part throttle

i agree with this by jikelly

well, the secondary circuit doent have metering rods..
the metering rods in the primary circuit will have a small affect on the WOT and a larger affect at cruise.. so if your cruise is fine, i would leave the rods alone and go straight to the secondary jets

you can probably go to the local autozone or orielleys and get an adjustment kit
which you MUST have to change jets.. because thats where you get the extra jets

how long have you had the carb on the car? when did the problem start?
because another thing i would check, is to make sure your getting enough fuel pressure
make sure your you dont have a clogged fuel filter; make sure your fuel pump is working correctly and then if neither of those things help; as your about to put larger secondary jets in, check for dirt and make sure everything is somewhat clean

goodluck, hope this helps

RaSMG · Mar 6, 2004

tuning an edelbrock ? i didn't know there was such thing, maybe changing parts in them .. those carbs have a mind of their own, no matter what you do or change they will do what they want. if you want tuning get a holley, if you want something you don't have to tune then that's what your edelbrock is for. in my experiences at least, i gave up on carter/edelbrock carbs the first time i realizes how easy it was to build/rebuild/tune a holley.

Jonstantine · Mar 6, 2004

and they started putting AI in carbs when?

because i know my carb does what it wants and not what i want it to..
but maybe thats because of the extent of my tooling skills
--------------------------------------------------------------------

how long have you had that tunnel ram intake? ive heard of some of those can cause problems

also, i really like your car, well everything but the taillights

88 Fox GT · Mar 6, 2004

RaSMG said:
tuning an edelbrock ? i didn't know there was such thing, maybe changing parts in them .. those carbs have a mind of their own, no matter what you do or change they will do what they want. if you want tuning get a holley, if you want something you don't have to tune then that's what your edelbrock is for. in my experiences at least, i gave up on carter/edelbrock carbs the first time i realizes how easy it was to build/rebuild/tune a holley.

Tried a Holley on it. The throttle response compared to an Edelbrock sucks.

Jonstantine, the carburetor has been on there since we put the engine in the car. My fuel filter is fine and there is no blockage. It has done this sputtering at WOT ever since we got it in. I just had other things to take care of before doing this.

RaSMG · Mar 6, 2004

I'm not sure if you get what I'm saying .. sure the Holley didn't 'bolt on' and go like hell, that's the whole idea. Holleys require tuning, they require you to know about carbs, to know what you're doing, to know what will work better, and to know how to change it. Accelerator pumps, cams, jets, floats, power valves, it's all one complicated formula but once you get it right it will run how you want it to, definitely better than an edelbrock, and you can work on any carb from then on. As you said, you bolted on the Edelbrock and it ran fine, good throttle response but top end sputters, do you see where I'm going with this? The edelbrocks/carters are not a 'performance' carburetor. They are a 'street' carburetor for people who want to bolt it on and cruise down the street or wind it up to an ungodly 4500RPM and not have to do any tuning. No matter how much 'tuning' ie changing those horribly labeled and arranged parts you do it won't be as 'right' as a Holley that's tuned in .. go to a race track and see what 99% of the carbed cars are running, holleys or variations of holleys like demon, bigs, etc. The other 1% either have webber stacks or edelbrock sponsors.

Jonstantine · Mar 6, 2004

Speed_Demon1965 said:
Tried a Holley on it. The throttle response compared to an Edelbrock sucks.

Jonstantine, the carburetor has been on there since we put the engine in the car. My fuel filter is fine and there is no blockage. It has done this sputtering at WOT ever since we got it in. I just had other things to take care of before doing this.

well, you wanna try changing to a larger secondary jet
so look into finding a kit that has different "edelbrock" jets and rods and stuff

i went to orielly's once and they pointed me to holley jets.. and i was like, this is not gonna work... i would expect someone who works at such shop to know... alas

also, do some research on that tunnel ram, cause those are definitely not meant for the street... that could be your problem too
and your throttle responce will be better without it too

Rasmg - i have no problem winding over 4.5k rpms with my edelbrock
holley's do make a bit more power, but thats WHEN they're tuned right
and if your a novice, that can be hard to do/learn
and especially for a daily driven classic, all i need is something else to mess with
having said that, when i get another car and run out of other areas to improve on my stang - more than likely i will put a demon (not a holley) on the stang (yes i know a demon is an upgraded holley)

jikelly · Mar 6, 2004

I will tell you that while there are some drawbacks to the carter/edelbrock carbs (fuel level control when cornering) I would say that it is a performance carb and, I think, extremly easy to tune. Being able to change the jets without draning the fuel bowls is a big plus and the metering rods make life real easy. Once you get your primary and secondary jets in the ballpark minor, adjustments are made with the rods.

I have used a carter on a few different engines and was allways very satisfied with how it managed air/fuel flow through my engine. I would say that there is a learning curve to getting them tuned and running the way you want but I bet the same thing goes for the holley style carbs also.

I had a guy try to convince me to swap mine for a holley once, but after a ride he changed his mind.

A strip kit which includes jets and rods should be around 50 bucks. I got a carter brand strip kit from jegs for 47. They tend to run a little more at the parts stores since they have the edelbrock name on them. You should be able to find jets at an advance, Auto zone, or Napa auto parts store.

jikelly · Mar 8, 2006

1967coupe · Mar 8, 2006

I had the same starting problem myself when I first got my Elelbrock yet the engine ran great otherwise. I ended putting in a size smaller primary jets and different springs and it went away...and wow what a difference. My pony really likes to get up and go now. No flat spots or sputtering that I've encountered up to 6K. You can't just put in a new carb and expect to get optimum performance out of it. Read the manual and get the jet/spring/rod kit and try different combos. BTW this car originally came with a brand new Holley and it was the most frustrating thing I ever had to put up with. One day it would run like a champ and the next it would be boggin out then run great again the next. I like the set it and forget it approach...unless you have the knowledge/patience to work with a Holley. I certainly don't have anything against Holley's and I would try one again but I don't think they're for everybody.

KK6695GT · Mar 8, 2006

An Edelbrock is basically just a re-badged Carter. Metering rods and jets just have a different numbering/sizing system.

A Carter is not a performance carb? I suspect you might have some ### kicking record setting Mopar drivers from the 60's argue that one!

I've used Holleys and Carters (and a couple Edelbrocks) myself over the years and personally I've always considered the Edelbrocks and Carters much easier to tune. Guess it all comes down to personal preferences.........

D.Hearne · Mar 9, 2006

I can't believe y'all Edelbrock/Carter guys started this thread. I thought these carbs didn't NEED tuning ? ONLY Holleys needed this stuff ?

jikelly · Mar 9, 2006

All fuel delivery systems need tunning.

Tuning an Edelbrock?

88 Fox GT

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