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post #1 of 22 (permalink) Old Aug 15th, 08, 01:44 PM Thread Starter
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engine idle

ive got a 350 with a quadrajet. it idles at about 1000 rpms which seems to be on the high side. i adjusted the idle screw all the way down as to not contact thte stop anymore. first, what should i be ildeing at? the cam is a very mild cam. how can i adjust to bring the idle down? i dont have an exact timing. if i retard the timing anymore, it startes to backfire out of the carb.

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post #2 of 22 (permalink) Old Aug 15th, 08, 01:47 PM
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Re: engine idle

Check for vacuum leaks.
Also it does not take much movement at all to retard the timing a few degrees and drop the idle speed.

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post #3 of 22 (permalink) Old Aug 15th, 08, 02:07 PM
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Re: engine idle

make sure the secondaries are closed all the way. had a carb where the secondaries were a bit sticky and wouldn't close all the way, couldn't idle below 1200 with the idle adjustment backed all the way out. a good dose of carb cleaner and worked the secondaries back and forth, problem solved.
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post #4 of 22 (permalink) Old Aug 15th, 08, 02:58 PM
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Re: engine idle

Make sure she's not on the fast idle cam, it's on the pass side of the carb.





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post #5 of 22 (permalink) Old Aug 15th, 08, 04:34 PM
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Re: engine idle

Did you make sure the engine was warmed up completely before making the adjustments? The choke needs to be in the verticle position. That way it's not idling on the fast idle(choke setting).

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post #6 of 22 (permalink) Old Aug 15th, 08, 06:04 PM
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Re: engine idle

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Originally Posted by angelglo View Post
i dont have an exact timing. if i retard the timing anymore, it startes to backfire out of the carb.
You probably need to advance the timing, then back off the idle adjustment screw ... Assuming you have a vacuum advance, you will need to pull and plug the vacuum line to initially set your timing. Afterwards, particularly if you are using full time vacuum, you will need to back off the idle speed after reconnecting time vac adv.
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post #7 of 22 (permalink) Old Aug 17th, 08, 07:07 PM Thread Starter
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Re: engine idle

john, i tried to retard the timing. when i do that just even a smidge, it starts to get bad response and back fires out of carb. i cant find any vac. leaks.

arron, the secondaries are closed all the way. its a freshly rebuilt carb.

charlie, i have it completely warmed up. i tried to do the adjustments affter i would go on a test drive.

i havent really tried to apply to much advance. i will try to do that on my next tuning session.

thanks guys.

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post #8 of 22 (permalink) Old Aug 17th, 08, 07:11 PM
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Re: engine idle

Did you pull the dizz (180* off). Also have you check the dizz to make sure its not off a tooth. Finally is the vacuum advance working.

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post #9 of 22 (permalink) Old Aug 17th, 08, 08:17 PM Thread Starter
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Re: engine idle

skip, are you talking about the distributor? its not 180 as it starts and runs fine. just idles a bit high at about 1000 rpms.

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post #10 of 22 (permalink) Old Aug 17th, 08, 08:23 PM
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Re: engine idle

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Originally Posted by angelglo View Post
skip, are you talking about the distributor? its not 180 as it starts and runs fine. just idles a bit high at about 1000 rpms.
Ok then have you hooked up a vacuum gauge up to it, maybe the advance plate is stuck. If you unplug the vacuum advance hose will th idle drop.

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post #11 of 22 (permalink) Old Aug 18th, 08, 04:29 AM
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Re: engine idle

You have a vacuum leak somewhere or the throttle plates are sticking open, push linkage with finger?

A stock SBC w/Q-jet should be able to idle down to 450 rpm, barely turn over, and pull 18"-20" of vacuum. Lots of good suggestions here. Tighten intake bolts, check hoses or disconnect them and plug the nipple(s), check fast idle cam has fallen out of the way, trans linkage, if automatic, is not binding?

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post #12 of 22 (permalink) Old Aug 18th, 08, 05:42 AM
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Re: engine idle

Also if you have power brakes make sure the diaphram in the booster isn't leaking vacuum. Either vacuum test it or plug the carb port to see if it makes a difference.
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post #13 of 22 (permalink) Old Aug 18th, 08, 06:09 AM
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Re: engine idle

I wonder if the linkage from the pedal is holding it up?
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post #14 of 22 (permalink) Old Aug 18th, 08, 03:36 PM Thread Starter
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Re: engine idle

blue, linkage is not being held up.

skip, everett, and jeff, those are things that i havent done yet. i will pull the vac. advance hose and see if there is a drop. i will also try t pull the brake booster line and check that also. i also push the linkage all the way closed with finger and no change.

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post #15 of 22 (permalink) Old Aug 19th, 08, 06:17 AM
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Re: engine idle

Maybe throttle shaft bushings worn and leaking? If you have a rich idle and now a vacume leak that could do it. Warped base plate? Mabe a lean idle and post nassel drip through main nozzle you can see it hit the base plate with a flsh light.. Just some thoughts
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