600cfm Edelbrock Performer Series Carb Problem

[sixtyfive]

This is a continuation of mustangman357's thread about his 750 edelbrock performer problem. http://forums.stangnet.com/showthread.php?t=718876

My situation is I notice a large amount of engine bog for the first few seconds when when I am at say 50% throttle and on up. This is of course apparent when shifting between 1-2 2-3 3-4. After the couple seconds of bog the car runs darn near perfect.

Not really "the cover"itself. the cover is there to cover it up. The problem exists because when butterflies slam open, it needs gas NOW. Or need to slowly oped (vacuum secondaries). Edelbrock is not really either.Jets and metering rods will not fix. Maybe overdoing the primary pump shot, but then milage and plug life will severly suffer. If you have anymore Q's, I would be happy to answer in one of your own threads though.

How is the primary pump shot adjusted?

I would likely see better gas mileage out of my 650 holley DP with a manual choke

I got to check my timing this weekend and I might as well put new gaskets and clean out the ol holley and give it a try to see what happens

 

[Z06killinSBF]

My Edelbrock does the same. Just waiting for my dad to build me up a Holley.

 

[sixtyfive]

Lucky me! the girlfriend works at 8 tommorow so I get all day to work with this problem. Ill check my timing and then throw the 650 on if I get it rebuilt before I work (i think all it needs is the bowl gaskets changed.

Is there anything I should look for when checking my timing specific to this problem?

 

[C0V3R]

Pump shot is adjusted using the little lever at the front drivers side of the carb. It has 3 small holes through it. Closer in will give you more shot, further out will give you less.

You might also want to look at your metering rods or step up springs.

 

[sixtyfive]

Pump shot is adjusted using the little lever at the front drivers side of the carb. It has 3 small holes through it. Closer in will give you more shot, further out will give you less.

You might also want to look at your metering rods or step up springs.

Oh ok!! yeah im in the middle hole right now, so i could adjust it a little.

It was mentioned already that the metering rods and spring would not help, maybe it is worth a shot however, are you running this carburetor?

 

[Fast63]

the metering rods and springs could help a great deal, but it is easiest to do the pump shot first, although the middle hole should be enough. I have run these carbs several times and I think they are highly misunderstood by some users and they revert back to holley :-\ I find that they are MUCH easier to tune and often run a lot better, but it seems some people have better luck with holleys. One of the critical things to keep in mind is that you cannot have over 6psi of fuel pressure with an edelbrock carb, cause it will blow fuel right past the needle and seat and into your engine.

 

[C0V3R]

Go a bit richer on the metering rods. Sounds like youve got a part throttle lean spot. Also try the other positions on the pump shot to see if either one helps you.

I've had similar problems to you with this carb and tuned them out with a combination of the above.

 

[10secgoal]

I will try to make this understandable without making it a thesis.
When carb throttle blades are opened, it creates an instant lean spot until gas start flowing from the main jet. Jetting has nothing to do with idle. You can put 99 up front, and it will idle the same. To "cover" the lean spot, a pump shot is used.Holley has over 100 different possibilities for pump shot variations, Edelbrock has only about 12.

Once the mains are "on," the jets handle all the fuel delivery. One way to get the mains to come one sooner is to raise the float level. Holleys are adjustable front to rear, Edelbrocks are not. There are even more ways for a holley that won't be touched here.

The mentioned above is the reason most around here call the shiny carbs Edelbogs. They lack the ability to tune out their flaws. Holleys have two versions of carbs. Double pumpers and vacuum secondaries. DP's are mechanical secondaires than when the pedal is floored, the front and rear butterflies slam open. That creates a huge lean condition. Lucky for us, holleys have a squirter in the rear and the front. Problem solved. The vacuum secondary style rears open at a specific rate depending on the size spring used. It is equiped with a squirter up front, but not the rear,like an edelbrock. Here's the difference. If a Holley bogs from a lean spot because the rears open too fast, you put a different spring to slow the opening until the bog is gone. It opens slow enough that the carb can start the rear jets flowing before a lean spot occurs. An E carb you cannot. It has mechanical secondaries. Yet it has no rear squirter, and no ability to adjust the timing of rear opening. It does have a plate above the rear secondaires that is weighted to try to mimick vacuum secondaries. So if it's not perfect for your app, your SOL. There is one way to attempt to fix. You throw in a squirter upfront way too big and drill another hole in the arm for the pump shot for more volume. This may be enough to cover the rear lean spot, but will certainly richen the front as well. And be entirely too rich when driving around.

Edelbrocks aren't horrible carbs if you aren't into performance, or want to ever floor the pedal. I hear they now have adjustable rears, but if you don't have it....Edelbrocks are usar friendly because there are less things to screw up if you don't know what you are doing, just like there EFI systems. Less timing tables and fuel maps make it easier to program. But you can't fine tune it like FAST or DFI.

Holley being more adjustable usually scares people away because they don't understand carbs. That included me years ago. Just because it has the ability to finer tune, does not make it harder to tune. It's a metered fuel leak. You just have to understand when,where and why, and you will understand why Holleys are better. Have you ever seen an edelbrock on a motor of a serious race car, or in a winners circle ? I'm not bashing anyone that runs them. I just feel if everyone had the knowledge some do about carbs, edelbrock would never sell another carb.

 

[Fast63]

It opens slow enough that the carb can start the rear jets flowing before a lean spot occurs. An E carb you cannot. It has mechanical secondaries. Yet it has no rear squirter, and no ability to adjust the timing of rear opening. It does have a plate above the rear secondaires that is weighted to try to mimick vacuum secondaries. So if it's not perfect for your app, your SOL.

You just said my favorite words! I've been trying to tell people for years that edelbrocks are mechanical secondary carbs.

The adjustable secondary you are talking about is their Thunder Series of carbs, I have never dealt with one of those personally, but it seems like it would be a good upgrade. My neighbor is an old school kind of guy and he told me that they used to do things like file material off the weighted flap above the secondaries or add material to it in order to make it come in faster or slower, so there are ways to change it, but that is really hokey

I think you are right that holleys have more potential for adjustability and pretty much everything you have said, but as far as comparing the carb for professional racing, that is kind of out of our league. The carb was not designed to go 7-8 seconds, it was designed for street machines like mine. I do like the edelbrock carbs for the street over a holley any day of the week, but yeah if I had to do all out competition, I would grab a holley/demon style carb.

 

[sixtyfive]

Edelbrocks aren't horrible carbs if you aren't into performance, or want to ever floor the pedal. I hear they now have adjustable rears, but if you don't have it....Edelbrocks are usar friendly because there are less things to screw up if you don't know what you are doing, just like there EFI systems. Less timing tables and fuel maps make it easier to program. But you can't fine tune it like FAST or DFI.

I agree with you here, the edelbrock gets amazing gas milage, actually its getting better then my quadrajet on a stock 305 But I do not really care what this car gets for gas mileage to begin with, if i were worried about that I would not own a v8.

My first step is going to be testing out the 650 DP in place of the 600 Edel. I know that I need to replace the gaskets on both bowls(they leaked when I last used it 2 years ago) Im guessing the holley is 15+ years old, is there anything I should do to it other then soakin it in some carb cleaner, blowin it out, and putting new gaskets on the bowls?

One other question is does any one know what the timing should be set at on a 347 with 430 hp at the flyweel? I can post up my specs if needed
My timing at idle is 12.5* and the MSD advances it to 25* at 3000 rpm

 

[10secgoal]

Gas mileage is mostly a function of what a motor requires. A holley can be made to get great mileage as well. That is one thing I do like about an E carb though. It is easier to do than a holley, and is not as permanent. But you can be more precise about it with a holley.
Blow out all the holes in the carb with compressed air.
I like to set the initial high at 18-22, or more if the car can start. And keep the total around 32-38. Checj it about 3k. It could have spring int it that don't fully advance until 5k. the same motor with 12 deg will wake up alot if it will take 20 deg initial.

 

[sixtyfive]

Gas mileage is mostly a function of what a motor requires. A holley can be made to get great mileage as well. That is one thing I do like about an E carb though. It is easier to do than a holley, and is not as permanent. But you can be more precise about it with a holley.
Blow out all the holes in the carb with compressed air.
I like to set the initial high at 18-22, or more if the car can start. And keep the total around 32-38. Checj it about 3k. It could have spring int it that don't fully advance until 5k. the same motor with 12 deg will wake up alot if it will take 20 deg initial.

Do you know much about the holley 650DP jet sizes? right now ive got 78 jets in the front bowl and 68's in the rear. Think this is too big for a 347? I want to run the car tommorow with the air breather off and see if the bog is still there, but my damn oil pan gasket is shot as well And the holley is just about ready to go on

 

[10secgoal]

Unless somwthing was severly changed in that carb, the jetting is way off. The front should be lower than the front, and by about 10 jets. I would try 75/85 first. This is not set in stone, just somewhere safe to try. When you make a jet change, always do the same to the back as you do the front. Taking jet from the front and adding it to the rear for gas mileage is worng.

 

[sixtyfive]

85??? isnt that insanely huge? I thought 78 was too big for my setup even, the other guy I know runs larger in the front then in the rear too but I think for testing purposes ill run it as it is now.

Someone else mentioned that I should try it with the air breather off to see if that is restricting my air flow at all

Ive been waiting to try and figure out which oil pan gasket I should use (4pc, 1pc) is the 4 peice the best one to use? on a 302 block?

 

[10secgoal]

If the power valve is blocked, then the number in front to rear should be the same. If it has one and hasn't been modified it shouldn't be but a 10 jet size difference. Mustangs and Holley's are alot alike. Everybody and their mother has messed with them before you got it. And most of them don't kow what they are doing.

 

[sixtyfive]

good news, tried it with the pump shot set to the top hole and the bog was almoast all the way gone

I belive part of my problem was with too low of rpm shifts when I am on it, when I run it to atleast 5400 rpm before I shift the problem is nonexistent.

I diddnt get to drive very far due to the oil pan still leaking, I gotta figure out whether I need the 1 pc or 4 pc gasket.

Thanks for your assistance, I think ill stay with the edel for now and mess with the jets in the spring if i ever feel the need to, I cant belive it was such an easy fix and I did not think to adjust this earlier!

 

[C0V3R]

Great to hear it helped out. As much as people bitch about them edels aint too bad for a daily.