Replace Edelbrock 1406 1557 or re-build? How do I get idle down? - Page 2 - Chevelle Tech
Troubleshooting Diagnosing problems done here.

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post #16 of 27 (permalink) Old Nov 14th, 19, 1:39 PM
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

Jim
On the NSCC post I was thinking that the engine would kill if you put it in gear with idle at 750, sounds like I have misunderstood the problem. So I think what you are saying is the engine "will" idle after putting the trans in gear with the engine at 750 but you cannot accelerate away, is that correct? If so sound ls like accelerator pump shot is week, and or float level low. The vacuum advance can contribute to a stumble/flat spot if timing is retarded enough at tip in, but with 14* you should be okay.
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post #17 of 27 (permalink) Old Nov 14th, 19, 5:07 PM Thread Starter
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

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Originally Posted by Bob's_Place View Post
Jim
On the NSCC post I was thinking that the engine would kill if you put it in gear with idle at 750, sounds like I have misunderstood the problem. So I think what you are saying is the engine "will" idle after putting the trans in gear with the engine at 750 but you cannot accelerate away, is that correct? If so sound ls like accelerator pump shot is week, and or float level low. The vacuum advance can contribute to a stumble/flat spot if timing is retarded enough at tip in, but with 14* you should be okay.
I guess I continue not to explain the problem correctly. You interpreted the NSCC thread correctly . With idle at 750 and foot on brake, if I shift into drive and either continue to keep my foot on the brake or release the brake the car stops.

If I have the rpms at 1100 then car runs with foot on the brake, or moves ahead if I take my foot off the brake.


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post #18 of 27 (permalink) Old Nov 14th, 19, 9:56 PM
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

Another words the engine will not carry the extra load caused by the trans going in gear,or will kill if idle is at 750, correct?
If there is good response to the mixture screw, they are somewhat even, and the engine will almost or will kill when ether mixture screw is turn in, than I think the idle circuit is working as it should. There may be other reasons to go into the carb but to through a kit at the carb I don't think will fix the idle problem.
So next check for vacuum leaks, carb base should be good, but did you recheck after reinstalling the carb?
Remove the booster vac line and plug. BE CAREFUL TESTING as you have no assist for the brakes when putting the trans in gear!
Next check for intake manifold to cyl head vac leak by pulling the PCV, put a piece of tap over the valve cover hole and plug the vent on the other valve cover, if the tape wants to draw in, the intake is leaking internally.
The timing should not change going in or out of gear. Watch the timing while turning the idle screw in or out, the timing should not move... Go back and read post #3 in Advance Limiting HEI vacuum advance... the easy way | NastyZ28.com

Good luck
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post #19 of 27 (permalink) Old Nov 15th, 19, 4:21 PM
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

Quote:
Originally Posted by nashville beth View Post
For a stock-type 350 with a spreadbore intake you can't do better than a Street Demon 625 IMHO

https://www.summitracing.com/parts/dem-1901/overview/
he would have to run an adapter to run this carb on his currant intake
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post #20 of 27 (permalink) Old Nov 15th, 19, 5:37 PM Thread Starter
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

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Originally Posted by p40 View Post
he would have to run an adapter to run this carb on his currant intake
Edelbrock adapter is installed.


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post #21 of 27 (permalink) Old Nov 16th, 19, 7:43 PM
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

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Originally Posted by p40 View Post
he would have to run an adapter to run this carb on his currant intake
The Street Demon and Eddy 1406 are both spreadbore carbs.

Summit says : Features black aerospace composite fuel bowl with ball burnished aluminum top and throttle plate.
Fits squarebore or spreadbore intake manifolds.

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post #22 of 27 (permalink) Old Nov 16th, 19, 8:41 PM Thread Starter
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

I donít know about the street deacon; but the 1406 I have is definitely a square bore. It fits speadbore intakes with either an adaptor or a special plate Edelbrock sells.


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post #23 of 27 (permalink) Old Nov 18th, 19, 12:29 AM
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

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Originally Posted by Jim_66SS View Post
...the 1406 I have is definitely a square bore. It fits speadbore intakes with either an adaptor or a special plate Edelbrock sells.
That's right, ALL 1406 carbs are square bore...

Once you go RAT, you never go back...
TC #1366

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post #24 of 27 (permalink) Old Nov 18th, 19, 4:52 PM
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

"Why chase timing specs when the problem can be carb related only?"

WWWWEEEEELLLLLL, idle quality and overall performance, engine heating and other factors will e adversely affected if the timing is not correct, especially carb settings.

If I read correctly, you have INITIAL of 14 degrees, and idle of 28? TOO MANY IDLE DEGREES.

Engnes do not like more than 22 to 24 IDLE degrees of timing. So, how to get there with full manifold vacuum sourcng? Well, not so hard, stop down the vacuum advance degrees.

HOW? With an adjustable degrees stop scroll plate attached the right way, to the vacuum advance (works on both stock type and adjustable vacuum advances). Crane/FAST p/n 99619-1 (Summit, Jeg's) When mounted properly, this stop will give 2 crankshaft degrees per serration of the stop, or, can be set wide open, to locked out. Mountng is easy, drill.tap 8/32 screw hole, mount plate and screw/washer, cut off excessive threads on the bottom of the advance, install, set, go. done. Low cost, Crane plate, and the screw, washer from the hardware store is less than a five dollar bill.

That way, the initial of 14 would allow easy starting, and once the vacuum came up in the engine, the idle timing would go to 22, 24, whatever degrees you select setting the degrees stop to.

OK, wise guy, how do I do that? Well, sir, ask for the complete stop plate packet here: [email protected]

They are absolutely FREE, with NO STRINGS, and, YOU can do the mods all by yourself. Works on either GM points, or large HEI distributors.


There is one picture that shows a fixed steel srtap to the vacuum advance, and it is also OK, but not adjustable. Home made, low cost (two 6/32 hardware store screws).



To set the degrees stop with the home made stop, use these degrees specs:


8 degrees: .086 inch
10 degrees: .112 inch
12 degrees: .135 inch


As far as getting the mechanical curve right, you might try one of two things.

First, look at the weights and center plate under the rotor, you want weights marked 41, center marked 375. This will give you 22 crankshaft degrees of timing to add to the 4 initial, for a 36 degree total timing, just where you want it. These parts are from the Chevrolet ZZ crate engine series.

Second, most of the aftermarket HEI builders use these parts as their default parts, might ask one of them for a set, if you can't find reasonably priced OEM parts.

Do not use one of the large HEI "recurve kits" available, they are NOT for street applications. They are designed to delete the vacuum advance use, and jack the initial way up for DRAG RACE USE ONLY. However, the mechanical advance springs in those kits do work for street use.
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post #25 of 27 (permalink) Old Nov 18th, 19, 6:21 PM Thread Starter
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

Will do Dave, soon after I recover my my hernia surgery. First I have to take the car into for a little paint/repair to the hood. Then its on the the distributor. Thanks,


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post #26 of 27 (permalink) Old Nov 18th, 19, 7:09 PM
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?

Quote:
Originally Posted by Jim_66SS View Post
I donít know about the street deacon; but the 1406 I have is definitely a square bore. It fits speadbore intakes with either an adaptor or a special plate Edelbrock sells.
Edelbrock says :

Primary Bore 1.44; Secondary Bore 1.69

I've never seen a square bore 1406. Maybe they exist ?
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post #27 of 27 (permalink) Old Nov 18th, 19, 8:41 PM Thread Starter
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Re: Replace Edelbrock 1406 1557 or re-build? How do I get idle down?



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