Edelbrock Carb help

[Andrew Loehr]

Hi all , i have a 86 gt that i rebuilt back in march , its a mild 306 , and i did away with the efi and put on a carb . I had an odd holley given to me and i used it for a while but could never get it to run right , so i bought a used eddy 1405 and cannot get it to idle , when it drops bellow 1300 rpms it will die or idle will surge up and down and then die like it has a air leak , but i have checked and cannot find one , and the holley idled just fine , just didnt perform like i wanted , and seemed like it blew a power valve everytime i started it . I put a rebuild kit into the edelbrock , adjusted the floats , adjusted the idle mixture screws , checked for leaks , used a vacuum gauge it reads 15hg and and will jump back and forth up to 17 , wont hold steady , but the rpms arent holding steady either . I dont think the metering rods are bent , but i tried pulling them up while running and it seemed like it picked up im also going to put some different step up springs in it and maybe jets but i wouldnt think that it would cause that , and it seems to be ok being choked but when you open the choke it falls flat , above idle its great , has great throttle response and runs good so im kinda baffled , any help would be great , thanks . Andrew
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[gearheadboy]

Hi all , i have a 86 gt that i rebuilt back in march , its a mild 306 , and i did away with the efi and put on a carb . I had an odd holley given to me and i used it for a while but could never get it to run right , so i bought a used eddy 1405 and cannot get it to idle , when it drops bellow 1300 rpms it will die or idle will surge up and down and then die like it has a air leak , but i have checked and cannot find one , and the holley idled just fine , just didnt perform like i wanted , and seemed like it blew a power valve everytime i started it . I put a rebuild kit into the edelbrock , adjusted the floats , adjusted the idle mixture screws , checked for leaks , used a vacuum gauge it reads 15hg and and will jump back and forth up to 17 , wont hold steady , but the rpms arent holding steady either . I dont think the metering rods are bent , but i tried pulling them up while running and it seemed like it picked up im also going to put some different step up springs in it and maybe jets but i wouldnt think that it would cause that , and it seems to be ok being choked but when you open the choke it falls flat , above idle its great , has great throttle response and runs good so im kinda baffled , any help would be great , thanks . Andrew
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I've only owned one of these carbs before and it was a long time ago. It was easy to adjust but I never cared for it. I will tell you a trick I do sometimes to fix idle circuit clogs. Carefully run the engine with the air cleaner off. With it running rev it up a little with your right hand and with your left place a clean old tshirt over the carb like you are smothering it. With your right hand rev the thing, open the throttle way up. If there is a piece of dirt in an idle air passage this sucks it out. It sounds as though you need to troubleshoot the idle circuit. Look at the Edlebrock website.

 

[Andrew Loehr]

Thanks for the tip , i tried it but no dice , is a good idea tho ! , It seems like the floats are sticking , like its emptying out and trying to fill up causing it surge. It also seems like an air leak that was my first thought and have went over it several times with carb spray but with it idling like that its so hard to tell plus the other carb didnt do this , and the mixture screws i started at 2 turns out and they dont make much difference at all even turning them almost all the way out , it is deffinatle running to lean and pops out of the exhaust , also on the metering rods i popped them up while it was running and it seemed to idle a little better like it was starving for gas , guess ill try adjusting the floats again for the 3rd time , also i put a regulator on and set it to 5psi (was running at 7/12 ) when i put this carb on so i know its not the fuel pressure . The motor only has about 900 miles on it since i rebuilt it dont know if that would matter tho it should be broke in by now . When i rebuilt it the 2 things i didnt replace were the lifters and push rods , i probably should have but spent way more than i intended . Thanks for your reply .

 

[gearheadboy]

Your fuel pressure should be about 7 psi in my opinion. To adjust your idle mixture (when the carb is working right) you need to connect a vacuum gauge to a manifold vacuum source. It can be on the carb but it has to be manifold vacuum, not ported. Adjust one side at a time. Tighten the screw until the engine starts to get rough, then count the turns as you back it out until the vacuum is at its highest. Lets say it takes 2 turns. Split that in half. Turn it back in until the engine starts to get rough again and back it out the 1 turn (half) and you are done. The metering needles don't control idle. The idle circuit does. When I think surge with a carb I think above idle. Rough or unstable idle is usually an air leak. Since everything else is the same its carb or carb related. Correct base plate gasket causing an internal or external leak? Being the Edelbrock and most Holleys are a different base bore design, do you have an adapter that may be warped or did you change intakes? How bout a pic?

 

[Andrew Loehr]

There are the best pics i could find of it . It is a square bore intake , there was an adapter/spacer on it in that pic but i have since taken it off i only had it on there for clearance reasons with that hei dist which i wish i hadnt of got now , and i have new gaskets under it , the intake is a weiand 180 , im starting to wonder if the base plate on the carb is warped i sure hope not . The fuel pressure i was just going off of edelbrocks book, says no more than 6.5 psi and ideal is 5- 5.5pdi, and iv heard people say that eddys cant stand the pressure as well as holleys . Yes it does sound like an idle circuit problem i blew compressed air through it when i rebuilt it . I also put an vacuum gauge on it and it read15 and would slowly go up to 17 and then back but that was at kind of a fast idle , at about 1k it was down to 11hg and jumping up to 13 .

 

[gearheadboy]

Makes some sense now. Your Edelbrock is a spread bore. Meaning the primary butterflies and the secondary ones are different sizes. MOST Holleys are square bore. Meaning the primary and secondaries are the same size. The Holley you have pictured is one of the only non factory Holleys to be a spread bore. It also is a different configuration as the bowls don't come off. It has a removable top. It is not a very good piece. I'd like to see the intake opening. If it is square bore you need an adapter. That "spacer" you have appears to be an adapter. It has a tapered opening from spread bore to square bore. If your intake is a spread bore opening, you can leave it out. Go with the recommended fuel pressure. I always use 7 psi as a guide. 5 seems low but they built the thing and know what it takes to overpower the needle and seat.

 

[Andrew Loehr]

Yes your right that is an adapter , i just used it as a spacer when i needed it , and that holley is junk , theres a reason they only made them a few years lol , as far as the intake it is a square bore (ported) it has the divider running in the middle of it but from what i understand edelbrocks are considered square bore carbs even tho the sec. are slighty lager than the primaries , like a QJ is a spread bore because the sec. butterflies are a good deal farther from the primaries than a square bore and also arent in a square pattern (more like a triangle ) like a holley , i also thought that eddys were spreadbore carbs and maybe i heard wrong and they are , ill give that adapter a shot tomorrow anyways .

 

[Andrew Loehr]

no luck with the adapter, should there be fuel dripping out of the primaries at idle ?

 

[Andrew Loehr]

Also noticed when i adjusted the floats the other day that they were sitting cockeyed , would that cuase them to get stuck on the baffles in the fuel bowl ?

 

[gearheadboy]

There should not be fuel dripping in. No the floats should hang level like side to side from the pivot point, but will sit low on the unhinged side.

 

[Andrew Loehr]

Well there is fuel dripping out of both venturis at idle, I wonder what's causing it though?

 

[CarMichael Angelo]

Sigh,.....can I chime in? The Holley carb you have is Not junk. it works well enough that Summit bought the rights to the design, and now markets that carb under their name. It is the same carb that was on my motor and worked flawlessly. It does have a bunch of innovations that conventional holleys dont have, starting w/a top that can be removed w/ fuel in the bowls, allowing access to the jets (front and rear at the same time) making jets changes much easier. The jets are the same as regular Holleys use. It has removable (and therefore tunable air bleeds as well as tunable idle air bleeds) it uses center hung floats additionally.
The reason it was discontinued is for reasons already mentioned in this thread,.......nobody understood it.
As for the Edlebrock,...there is clearly a problem that was present when the previous owner had it (hence it was sold). You can bang your head on a carb for several days/ weeks and it still may not ever be right. If it has some piece of junk in the idle circuit, it may never come out,...and adjusting float levels will not cause the condition( or solve it) you are describing.
If the Holley works, why not tune on a carb that will at least do what it's supposed to, as opposed to the non working Edelbrock?

 

[CarMichael Angelo]

Well there is fuel dripping out of both venturis at idle, I wonder what's causing it though?

Of course there should be fuel dripping in out of the venturies at idle,......what do you suppose is keeping the engine running? The reason it's happening is how a carb works,....engine vacuum is drawing in fuel through the venturis,....and it is being dripped in through the idle circuit.
The only time there should not be fuel dripping into the engine is when its NOT running.

 

[Andrew Loehr]

Thanks for the input , yes i know that thats were the fuel comes from drawn by vacuum , just hadnt paid attention to it i guess before . I would rather fiddle with this edelbrock than mess with that holley , i have had a bunch of holleys and have liked them but i really prefer eddys , and have not had much trouble out of them before , and that holley is a simple design for sure , just dont care for it . Ill try going through that idle circuit again with some fluid and air and maybe something will come out ,thanks for your info .

 

[gearheadboy]

Maybe I am using incorrect terminology or something. Not trying to dispute your knowledge at all, but in my experience the fuel dripping in is not normal. I found this on the Edelbrock troubleshooting page as well.I would assume that an incorrectly positioned float would do the same. He did have it apart and said they looked out of position.

Q: I see fuel dripping from the carburetor boosters at idle, what causes this?
A: Too much fuel pressure usually causes this and often times dirt in the float bowls can do the same. Make sure your fuel pressure does not exceed 6.0 psi, optimum pressure is 5.5 psi.

http://www.edelbrock.com/automotive_new/misc/tech_center/install/carb_faq.shtml

 

[Andrew Loehr]

Yea thats what i was saying , i know thats were it comes from just dont remember it being like this, a constant drip like a leaky faucet , i suppose an air leak could cause it to do that im not sure , but i am sure its been running to rich , took a plug out and it was black as could be , going to have to take those floats off again .