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Discussion Starter #1
Hey guys,
May be a long shot, but our big inch motor has a weird stumble around 4500RPM. Runs like a bat out of hell but in the burnout it stumbles until it clears up, then takes off. Doesnt really effect us on track, but is annoying.
Motor has split dominators on it. Some people have mentioned pulling the air bleeds all the way out, make a run, and see if its better. If so, slowly step down in size on the air bleeds until the stumble comes back, and then go back up a couple sizes.
We're by no means carb experts so thought Id see what peoples opinions were???
We cant really think of anything else that would cause the stumble. Motor is sealed up really well, with no apparent vaccuum leak or anything.
Any and all input is appreciated!
Thanks!
 

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Do you have an A/F meter on the car? The stumble could be a lean stumble which would need more fuel to correct. If its a rich condition causing it, then that could help. Just remember that if your a/f ratio is good up top and you lean the intermediate, you'll have to add jet to compensate for the fuel you took away.
 

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Hey guys,
May be a long shot, but our big inch motor has a weird stumble around 4500RPM. Runs like a bat out of hell but in the burnout it stumbles until it clears up, then takes off. Doesnt really effect us on track, but is annoying.
Motor has split dominators on it. Some people have mentioned pulling the air bleeds all the way out, make a run, and see if its better. If so, slowly step down in size on the air bleeds until the stumble comes back, and then go back up a couple sizes.
We're by no means carb experts so thought Id see what peoples opinions were???
We cant really think of anything else that would cause the stumble. Motor is sealed up really well, with no apparent vaccuum leak or anything.
Any and all input is appreciated!
Thanks!
I did that before and went way lean! put back in and opened up original orifice size a little at a time till it went away.
 

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Discussion Starter #4
Good info guys. Thanks. Maybe we'll just step up a few numbers at a time to see if it helps any. Its weird thats its only one small RPM window, but we cant find anything else that would cause this condition. Any other ideas?
 

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I had a similar problem and removing the intermediate bleeds got rid of my stumble at part throttle, and on the launch, but down track it went way lean and my mph fell off 5-7 mph. I suggest getting a numbered drill bit set and increasing the size of them, rather then completely removing them.
 

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Runner lenghts on the intake can cause reversion issues in some RPM bands. Its not really a miss more like random mixing up cylinders on power but not dead just above and below it will be just fine but always the same window same problem.
 

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Discussion Starter #8
Weird thing is it never did it before going in for a freshen up last time...since then its been there, and we cant figure out why its there. Same intake, and the carbs/intake were taken off the motor, set on a shelf, then re-installed...never messed with. Really not sure what it is, just grabbing for any ideas we come across. Thanks guys.
 

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Maybe Clean them really really good, I had that with my pro systems 1100 dommy, and i went down # wise on the bleeds till it went away, same thing as you, It's a lean spot......fatten the intermediate up alittle, Mine took about 10#'s, went from 74's to 63....... and it was still deadly consistant
even pick up the 330 times alittle..............
 

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I like IceCream
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Maybe Clean them really really good, I had that with my pro systems 1100 dommy, and i went down # wise on the bleeds till it went away, same thing as you, It's a lean spot......fatten the intermediate up alittle, Mine took about 10#'s, went from 74's to 63....... and it was still deadly consistant
even pick up the 330 times alittle..............
I am spoiled........I just call Tom......tell him the weather data, and he tells me bleeds and jets......I plug it in, and it runs great. :p
 

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pig hunter
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how long did they sit? i have had spiders make home in a few carbs or small bugs.. pulled it apart and found all sorts of shit.. if you just had the engine freshed with no changes i wouldn't do shit to the carbs as for changes. if you changed anything then you may need to adjust
 

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Discussion Starter #12
Nothing has been changed. They sat on the shelf for probably 3 months...we had cleaned them out real well once, and thought it helped...but we were just being hopeful...it didnt fix the problem. We cant try to clean them again...just weird that the motor seemed fine before...nothing was really changed when re-building other than bearings.
 

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pig hunter
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pull every bleed and jet out a soak the fuckers good. take a piece of very small wire and make sure there is nothing blocking passes ans blow out good..
 
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