I cannot get the idle down. I've got it bolted to a 283. When I try to back off the idle screw the motor dies. I'm guessing the lowest rpm I can get it down to is somewhere between 1500 and 2000 before it dies. Air/fuel mixing screws do nothing when turned to any position. When I am able to get the idle down just before stalling...it cycles with a surge. for ex. 5 seconds at a lower idle(1500rps's approx.) to 5 seconds at a higher idle(2000 rpm's approx.) and this repeats. Also covering the carb with my hand or adding some choke keeps the engine from dying. Timing is pretty close but I can't dial it in with the idle so high. The idle is flat(no surging/cycling) when the idle is 2000(approx.) or above. Things I have tried..... -tried replacing metering rod springs. (with all 5 sets available in kit) -rebuilt carb. -checked fuel pressure(at about 4.5 lbs.) -checked for vacuum leaks(tubing,intake and carb) I have had the truck for a couple months now and has been this way since I have owned it. am I missing anything? Chuck
From your description, I'd have to guess there is still a vacuum leak there somewhere. Did you have the intake off or just the carb? Are the secondaries fully seated?
Try checking for an intake manifold leak. I chased a similar problem for a while until I retightened the manifold.
Yeah I took the intake base off, cleaned it and resealed it. Sprayed carb cleaner all over the place and found no leaks. Put a mighty vac. on all my hoses and they come up clean. Manifold pulling 21" of vacuum by the way. "Secondaries fully seated" Not sure what you are referring to here so I'll have to say I don't know. How do I check for that?
if you cover the top of the carb with your hand while it's running, does it stay running or die after a few seconds? if it stays running,you are getting air from somewhere other than the venturis.
It continues to run after the idle bumps up a bit. I have blocked off every vacuum port on the carb and I still get the same results....Just sprayed carb cleaner all around again and didn't notice a change in the idle.
You should have 3 ports on the front and one on the back. If it's still running after you put your hand over the top to block out the air it's still getting air from somewhere.
Look around the intake for open ports, if you have a vacuum advanced distributor it may be ****ing air from the advance also.
i had the same trouble with mine as well. i had two on my small block they were 650's what i did was buy a new gasket kit from edelbrock and rebuild them ..when i cracked them in two there was alot of old dirt and **** sitting in the bowls ( i dont know if yours are new mine were used and than sat .. after i clean everything out i put it all back together set the air idle screws as edelbrock suggest 1 and 1/2 turns out on both side screws ..ran great idled down perfectley good luck
i agree with lorodz bout 1 1/2 turns out on air fuel screws. did u happen to check the floats when u rebuilt it. i believe edelbrock calls for 5 or 6psi fuel pressure. get a manual it will show u how to set everything.
6 psi .... and there tech said 1 and 1/2 turns out on both screws evenly yes floats were stuck up so i took the pins out rmoved the floats and then the needles dropped out i cleaned both of them with a br*** wire brush only..that re installed everything ..only thing i recomend is to stretch the springs when you take them out a small amount evenly helps alot
Spray carb cleaner into the breather on a valve cover on both sides if possible, if the idles speeds up, the vacuum leak is from the intake into the valley. Everything you are describing sounds like vacuum leak.
At idle the secondary thottle plates should be fully closed. Make sure nothing is interfering with the carb linkage that may be holding the throttle blades slightly open. You may be able to open the secondary air valve and see if the throttle blades are not fully seated. If this is a used carb, did a previous owner drill any idle air bleed holes in the throttle plates. This kind of a modification isn't usually needed on a stock or even mildly warmed over engine. Good suggestion to check brake booster, vacuum advance, vacuum modulator or any other vacuum accessories also to make sure they're holding vacuum.
The baseplate for the offy manifold on my 292 was warped, and gave me similar trouble. that. Might wanna check that, if there is one.
Great!....keep the suggestions coming. The two new ideas suggested are inspecting the secondary plates and spraying carb cleaning into the valve covers. I'll do that tonight when I get home from work and let you guys know. Also.....the truck is running pig rich....don't know if that changes anything.
Check for Vacuum leaks like everyone above suggested, and pull the top off and check for **** in the needles and seats and sunk or sticking floats - you said it runs pig rich, that's where I would start.
Did you try spraying around the front or back of the intake where it meets the block? I can also stop over for a little while this weekend and we can try that extra holley I have to rule out if it's the carb or not. -Rich
Not the response I was expecting from you Richie...... "just bleed the brakes and she'll be good to go." Yeah. I think we're ready to try that other carb. I'll be working on it tonight and Sunday.
Secondaries are indeed sealed while idling....no holes drilled into them either. Spraying carb leaner into the valve covers very slightly raised the idle on the p***enger side only. For those who think I still have a vacuum leak somewhere. Wouldn't the idle be constantly high and not cycle low to high like what I am getting? Even when I run the motor with the carb mostly choked, in a effort to get the idle down, the idle still wants to cycle. Although less noticeably.
Here's the latest. We swapped out the Edelbrock for a Holley and succsessfully got the idle down. So what ever it is is in the carb. We then put the Edlebrock back on to double check and we indeed could not get the idle down without the motor stalling. we also sprayed all the entire carb and found no external leak that shouldn't be there. We did again notice that covering the Edlebrock carb with our hands caused the idle to jump up. We had the oposite effect when we did that with the Holley on. Any thoughts at this point. Chuck
Loose tubes into the carb body for the front two vacuum tubes. Crack in the thread in large hole in the back of the base plate. Warped base. Stuck metering rods (not sure if these would cause this).
I would contact Edelbrock, They have been very helpful on any problem that I have had. DON'T use the e mail. call and talk to some one.
I would check for bent or missing metering rods or stuck piston things that the metering rods hook to. Also, drop the fuel pressure - 5.5 max on an edelbrock.
thats why i suggested to take the cab apart i just went threw the same thing with 2 650 on my tunnel ram the metering rods needles and spring needed to be cleaned your not gonna find out the problem till you crack the carb open ...goodl luck
they are very picky about to much pressure, they need to have a regulator and I have best luck with setting it at 5psi, if you have more than 6 the carb does not like it. Since the springs are an important part of how the Edelbrock meters fuel I recommend against this, if you want to change the springs get the spring kit and actually tune the carb. What's the fuel pressure? Is there a regulator? To much pressure and it'll push right past, just checking the pressure doesn't always help, it'll climb and fall, I highly suggest a regulator. Are the floats set correctly?
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