Edelbrock idle circuit question

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pjc360

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I have a edelbrock performer 600cfm manual choke carburetor on my 360 magnum and i am trying to determine if the metering rods have any effect on the amount of fuel that my engine gets at an idle.
I know the idle circuit is seperate from the primary and secondary circuit, but doesnt the fuel from the idle circuit have to go by the metering rods and down the jet at an idle? I was running a pair of 70x47 mtering rods, and i changed to a smaller pair of metering rods wich are 68x42 metering rods and am hoping going down from a 70 to a 68 on the thicker part of the metering rod will expose a little more fuel to the engine at an idle.
 
They can under certain conditions. If you have a situation where you have a big lopey cam, and not enough initial advance, you'll have to crank the idle screw way up to get the thing to idle. THIS will bring the primary plates out of the idle transfer slots, and it will start to run "somewhat" on the mains.

NOW if you add to that mix, you have too strong springs on the metering rods, the rods may be up or bouncing up/ down because of the cam and low vacuum, then yep.....you'll have a mess on your hands.
 
well i have a steady idle, My vaccum at idle is about 16.5 to 17hg and i have plenty of initial timing and i am not taking the primary plates out of the idle transfer slots. I was just wondering if changing to a 68 from 70 on the fat side of the metering rod would make it a little richer at idle.
 
sireland i already have that book and i have another edelbrock carb book written by dave emunel. I just havent found the answer to my question wich is does the fat side of the metering rod have any effect on the amount of fuel the engine gets at idle, if the fuel from idle doesnt go thru the main jets then where does it go?
 
Once again you have managed to ask a question which has a meaningless answer, and the reason is, that EVEN IF IT DOES, that is not the way you "look" at these carbs.

You tune the main jets for cruise and full power NOT idle!!!. If you get the carb properly tuned for cruise and power, and the damn thing won't idle, then find out what is causing it. You cannot change the jets/ rods to get the thing to idle, and then wonder what to do at cruise and WFO

So the correct answer to the question as written is, "why does it matter?"

So ask the REAL question!!!

WHY do you want to know this? You have an engine that won't idle? There are many many other issues besides carb main jetting that can affect idle
 
no the engine idles fine, the reason i want to know the answer to my question is because i think it could use a tad bit more fuel at idle, my cruise and power are as good as they are going to get.
Sometimes when the engine is cold and idling i can hear a very faint (lean) miss fire out of the passenger side exhaust pipe only, so i think my leanest cylinder must be on the passenger side? Anyways once it warms up all the way its fine and idles great. So thats why i'm asking, I have tuned my mixture screws, i set them to the highest vaccum reading and then have turned them out about 1/4 turn each to make it a tad bit richer, maybe i need to back them out a little bit more.
I was just thinking maybe the diameter on the fat side of the metering rod would affect the fuel it got at an idle. But like i said its only a very slite lean miss fire at idle and its only when its cold at an idle, when it warms up its gone.
 
And its also been very cold where i'm at for the last couple weeks, its 12 below zero right now and its been 5 to 10 below everyday for the last 2 weeks, so maybe the thin cold air has something to do with it too.
 
When it's cold and the engine is warming up it needs a bit more fuel. All carb adjustments should be done when the engine is fully warm at operating temp. Don't mess with the main mixture to make your carb idle better when it's warming up. Then it will be too rich when the engine is warm. If you have a manual choke, run it half open till the engine is closer to being warmed up. You should get a electric choke kit for yours or a carb with a electric choke on it. Then you can tune the choke coil for cold idle. tmm
 
Well i bought an edelbrock choke cable, but i fought with it forever trying to get it to work properly and gave up, it wouldnt pull the choke fully closed from the inside. So ya an electric choke would be nice. thanks for the replies.
 
well i have figured a few things out that are interesting with this carburetor.
Number 1, i decided to take my 4 hole 1 inch phenolic carburetor spacer off, mainly because it made my gas pedal very stiff because of the higher angle and it made my idle a little lean. Anyways, after ditching the spacer i noticed a slight decline in lower throttle power but a huge gain in upper rpm power, and it cruises down the highway so much smoother without that spacer.
But as soon as i took the spacer off i had a huge stumble/hesitation when first poking the gas pedal, if i took off nice and easy it was all good, but any quick stabs of the gas pedal and it would bog like crazy. So i took the carb apart and found out my accelerator pump was very worn out, it was bent and wobbling from side to side very easily. So i bought a new accelerator pump and put it in, just the edelbrock replacement accelerator pump, its got blue on it instead of orange. I also took the squirters off and blew carb cleaner thru them and i noticed a wieght sitting on top of a check ball under the squirters, so i took that wieght out and left the check ball in and put it all back together with the new accelerator pump.
I put the accelerator pump linkage in the middle hole, and it seemed to help alot, i'd say the hesistation when abruptly poking the gas pedal is about 70 percent gone, but it still has a sluggish spot in the throttle when you poke the gas, so do i need to try the top hole of the linkage or the bottom?
My timing is perfect, 14 initial 32 total, no vaccum leaks, i have rock solid vaccum at idle of about 16.5 hg, i'm running the stiffest step up spring the silver springs with 68x42 metering rods. Another question i had, is how was this spacer able to cover up the weak accelerator pump shot? I never had a hesistation or a syumble with the spacer on at all. Then i take the spacer off and i notice it, what was the spacer doing to make the hesistation not noticeable at all?
 
Try putting that weight back on top of the check ball. My guess is, it's now dribbling fuel out the squirter all the time, and the stumble you're getting is a rich bog.

I find it mysterious that you seem to lack a fundamental understanding of how carburetors work, but you can diagnose a "lean misfire" only on the left side.
 
Well without the spacer there is no miss fire at all while at an idle.
And the only reason i removed the weight is because i was talking to a guy i know who is running the same carburetor on a fairly warm 302 ford in a 68 bronco and he said he was fighting the hesitation when abruptly hitting the gas pedal, he tried all the different accelerator pump settings and none of them helped and he eventually took the squirters off and removed the wieght that sits on the checkball and his issue was gone. But i know that just because it worked for him doesnt mean it will work for me, i was just simply giving it a try. I'm going to try the top hole on the accelerator pump and see what happens, if it gets worse then i will put the wieght back on top of the check ball.
what i dont understand is, edelbrock uses a weight on top of the check ball and sometimes they use a spring and the carters used a spring, why do they go back and forth from weight or spring on top of the check ball below the squirters?
 
It just a design difference, that's all.
A weight will work exactly like a spring does.
 
Any time you have a spacer under the carb, whether it's a open type or 4 hole, it changes things. In effect runner length and/or plenum volume is changed depending on the design and ht. of the spacer. That can throw the whole tune you had out the window. Thus the reason it acts so differently without the spacer.

And don't worry about a slight cold mis-fire. IMO it sounds like it was tuned really well if it had that but was fine when warmed up. You can richen it up if you like to get rid of the cold mis-fire but IMO all you'll do is cause it to get worse fuel mileage and possibly gas foul the plugs.
 
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