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Old 01-08-2017, 07:40 PM   #1
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Default Lean tip in

I dont have an ls, but a carbed first gen 383 in my 96 z28. I hope im not bashed for posting in the wrong section, but my question should be universal as far as carbs go. I have a holley 650 dp on top of an airgap. Front jets are 67, rears are 73. Squirters are 31 front, 35 rear. I finally have the car running great. I recently installed a wideband o2 gauge. I am idling at 14.3 - 14.8. Cruising at about the same. My issue is on tip in to medium or wide open throttle, I get a lean spike that jumps in the 18s. It only lasts a second, then recovers. Is this normal, the air moving faster than the fuel is catching up? The car doesn't feel like it stmbles at all. If it wasnt for the wideband, I'd never know it was happening. But..... I DO know, so if i can fix it, i would like to. I tried increasing front squirter and i was fouling plugs within hours. Any suggestions would be greatly appreciated. Maybe Its a sacrifice to be running so good everywhere else? Thanks in advance.
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Old 01-08-2017, 08:42 PM   #2
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idling at 14.3 is lean, I'll bet it is leaner than lean best.

Don't shoot for an AFR # at idle, you want lean best.
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Old 01-08-2017, 09:20 PM   #3
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The afr at idle seems fine to me. Us ls guys shoot for around 14s depending on fuel. I wanna say some serious carb guys pull and plug the power valves. I wanna say it helps with this situation. Also try bringing secondaries in sooner.
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Old 01-08-2017, 10:02 PM   #4
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Maybe try a more aggressive pump cam to bring a stronger shot in sooner?
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Old 01-09-2017, 07:45 AM   #5
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Classic case of needing to adjust the idle feed restrictor. Try going a size larger on the IFR and maybe one smaller on the idle air bleeds. If your carb doesn't have adjustable restrictors you can drill them out and replace them with brass set screws you drill yourself. Lots of info on line how to do that. The IFR works just like the main jets for the transition RPM's (idle to ~2-3K)

One thing, make absolutely certain your accel pump linkage is adjusted so even a slight throttle movement causes a strong shot. Should be zero gap in the linkage.
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Old 01-09-2017, 05:51 PM   #6
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Thanks everyone. I have heard about drilling out your own ifr's before. Maybe i will try that. Buy the concensus is that it can be fixed, right? Wasnt sure if it was normal or not. Everything is mechanical unlike efi so i wasnt sure if it was a byproduct of being slower than a computer to correct. Like i said, it only lasts for a second. I appreciate the responses. Thank u.
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Old 01-09-2017, 07:07 PM   #7
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You need to have lean best Idle, I dont give 2 craps what the AFR number is.
Tune it with as little dependance on accelerator pump as possible.

Plugging the power valve will make it worse.

A carb does not care if it is on an LS motor or not.

Depending on the accelerator pump for more than is necessary is a band aid and will lead you away from the path of enlightenment.

Last edited by RixTrix; 01-09-2017 at 07:16 PM.
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Old 01-10-2017, 04:42 PM   #8
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Quote:
Originally Posted by RixTrix View Post
Depending on the accelerator pump for more than is necessary is a band aid and will lead you away from the path of enlightenment.
My brother!
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