edelbrock idle problem - Team Camaro Tech
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post #1 of 8 (permalink) Old Nov 13th, 01, 04:47 PM Thread Starter
 
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Location: Albuquerque, NM USA
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I have a recently rebuilt chev 350 of about 1974 vintage. It was built with an "RV" cam. I don't know the specs of the cam. I recently put an edelbrock 2101 intake and 1405 mech choke performer carb on. I'm satisfied there are no vacuum leaks. Carb and manifold were installed twice very carefully. Intake with Felpro 1256 gasket and carb with an edelbrock 9266 divided heat insulator gasket. Ignition is fresh pertronics ignitor II. Coil is MSD blaster 2 - 8202. I live at 5500 feet and have jetted lean one stage in primary and secondary. Timing is set at 12 BTDC. I had a drip flooding condition that I solved with new inlet jets and float adjustment. The engine still won't idle right, however. I tried #4 step up springs to no avail. Idle adjustment screws make no difference bottomed out or completely removed. Seems to do better with choke partially closed. Plugs foul (wet) on cylinders 1,4,6 and 7. manifold vacuum is 10hg and compression on all cylinders is 125 to 130. Got any ideas?

[This message has been edited by Terry Farmer (edited 11-17-2001).]

[This message has been edited by Terry Farmer (edited 11-17-2001).]
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post #2 of 8 (permalink) Old Nov 13th, 01, 06:57 PM
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Joe
 
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I beleave 1,7,4,6 all run off the same side of the carb (that is if you have a dual plane manifold). I would look at that half real close. Mabey you have the idle screw to rich or a leaking gasket. Im not a carb expert but thats were i would start.



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post #3 of 8 (permalink) Old Nov 13th, 01, 07:19 PM Thread Starter
 
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You're right Joe Kool. I noticed that the plug fouling was all happening on the low side of the dual plane manifold. Should I replace the plugs, lean out the corresponding idle screw a bunch and try again?
Farmer

[This message has been edited by Terry Farmer (edited 11-17-2001).]
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post #4 of 8 (permalink) Old Nov 14th, 01, 10:07 AM
BC
 
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Terry,
I live in Colorado Springs which is about 6,200 ft and I think you are still way too rich. I usually have to step down three jet sizes to get close to what it should be. Also, Edelbrocks don't like much fuel pressure, I used to run mine between 4.5 and 5 psi. Seemed to like that better than the 5.5 or 6 like the book says. If you are not getting any change with the idle mixture screws, then it is getting too much fuel elsewhere. Does closing the choke plate kill the motor? It should. If not, then you probably have a vacuum leak somewhere. The step-up springs have no effect on idle qualities, that is for getting into the power circuit.

If you don't want to change the jets, try installing a rod a couple sizes bigger than what you have now. You will be getting close when you can actually turn the idle mixture screws and make a difference.

Good luck,
Bill C.


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Bill C.
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post #5 of 8 (permalink) Old Nov 14th, 01, 02:32 PM Thread Starter
 
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Thanks Bill. As soon as I can get it adjustable I will try your leaning suggestion to get closer to an optimum A/F ratio. Here's what I think is happening now. I had a drip flooding condition which I was able to cure with a fuel regulator, new needles and seats, and float adjustment. I'm running 5.5 psi now and it seems ok. I can reduce the pressure further per your suggestion if the flooding returns. After the flooding fix I was able to adjust the passenger side idle screw. The drivers side (low side of the dual plane manifold) remained unadjustable. I think the mistake I made was not replacing the fouled plugs after the flooding fix. I thought they would just burn off, but 1,4,6,7 are still missing badly. I'm hoping that replacing the plugs and leaning down the low plane side idle adjustment screw will fix the problem. I'll post the results. Thanks again.
Farmer



[This message has been edited by Terry Farmer (edited 11-17-2001).]
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post #6 of 8 (permalink) Old Nov 14th, 01, 02:47 PM
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You mentioned that the idle mixture screws have no effect; this normally indicates that the throttle plate is being held too far open by the idle speed screw and it's idling from the transfer slots instead of the idle mixture holes, which would explain why it's idling erratically and rich. Back down the idle speed screw to close the throttle plates down more and start with the idle mixture screws out about 1-1/2 turns and go from there. At a normal idle throttle plate position, only about .030" of the transfer slot should be exposed below the throttle plate.

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post #7 of 8 (permalink) Old Nov 14th, 01, 06:58 PM
XK1
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I agree with JohnZ- I've seen an Edelbrock have a normal idle speed running like crap because the idle speed screw was in too far. As I lowered the idle, it smoothed out and the mixture screws worked.

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post #8 of 8 (permalink) Old Nov 17th, 01, 06:15 PM Thread Starter
 
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posted 11-17-2001 04:14 PM
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Joekool came closest to figuring out what was wrong with my carb. He noticed that the problem seemed to be associated with one plane of the intake manifold. I changed plugs and leaned down that idle screw to no avail. It was still missing badly on 1,4,6,and 7 and the idle screw on that side wouldn't adjust. I took the primary venturi boosters out and found some trash in the small brass tube on the bottom of the booster on the side of the carb I was having trouble with. Cleaned it out and she now purrs like a kitten. Joekool spotted an important clue and made me concentrate my efforts on that one side of the carb. One hole, actually, the drivers side primary. Thanks, Joe.
Farmer
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