Re: Carb stumble
[Re: scarly10]
#2641163
04/04/19 01:09 PM
04/04/19 01:09 PM
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Joined: Aug 2003
Posts: 43,163 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,163
Bend,OR USA
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Does the exhaust stink when warmed up at idle? If so you need to lean down the idle mixture to help it not bog. If it doesn't stink try enrichening the idle mixture screws a 1/4 turn at a time to see if that helps get rid of the stumble You can make a carb stumble off idle by being to lean or to rich Do your squirters squirt fuel as soon as you move the throttle shafts any at all? If not adjust the screw so it does What brand and size is the carb?
Last edited by Cab_Burge; 04/04/19 01:11 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Carb stumble
[Re: scarly10]
#2641267
04/04/19 06:28 PM
04/04/19 06:28 PM
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Joined: Aug 2003
Posts: 43,163 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,163
Bend,OR USA
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Does it still have the stock undrilled throttle plates in it? Is it a four corner idle unit or the front only type? If four corner adjust all of them, if not do what you can If no extra holes in the throttle plates try the idle mixture screws and make sure the rear throttle shafts are not opened a bunch
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Carb stumble
[Re: parksr5]
#2641326
04/04/19 09:05 PM
04/04/19 09:05 PM
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Joined: Jun 2003
Posts: 9,225 Charleston
sixpackgut
Drag Week Mod Champion
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Drag Week Mod Champion
Joined: Jun 2003
Posts: 9,225
Charleston
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Blue cam on 30cc or put 50cc pump on it.
Gen 3 power 6.22@110, 9.85@135 Follow @g3hemiswap on instagram
performance only racing, CRT, ultimate converter, superior design concepts, ThumperCarbs
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Re: Carb stumble
[Re: crackedback]
#2641423
04/05/19 06:01 AM
04/05/19 06:01 AM
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Joined: Oct 2015
Posts: 570 UK
rb446
mopar
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mopar
Joined: Oct 2015
Posts: 570
UK
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"Blue cam on 30cc or put 50cc pump on it"
^^^^^this
We never had any hesitation issues on either the 750 or later the 850DP carbs we ran on my 340 car. However in an effort to make things even better with what we had we put a 50cc pump on the 850 and noticed a good improvement even on the street when testing, it had the desired effect at the track on the hit f/braking, and that carb was almost 2/10ths quicker in the 1/4 than the 750DP the car came with so a good gain for not a lot of money, just glad I used to think out of the box as everyone else at the time said that was too big of a carb for a small motor.
1969 'Cuda 446ci, best 9.96@133.9 in 1990 1971 340 'Cuda, best 11.01@122.8 in 1987
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Re: Carb stumble
[Re: scarly10]
#2641457
04/05/19 09:04 AM
04/05/19 09:04 AM
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Joined: Jun 2006
Posts: 5,161 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,161
CT
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Check the SECONDARY A/P adjustment
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: Carb stumble
[Re: scarly10]
#2641472
04/05/19 09:45 AM
04/05/19 09:45 AM
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Joined: Oct 2004
Posts: 3,097 back in Georgia
dthemi
master
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master
Joined: Oct 2004
Posts: 3,097
back in Georgia
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Get a spray bottle and put gas in it. Have a buddy (that you trust) stab the throttle On the brake, to the point where it stumbles. be ready and give it a spray from the bottle. If it's better you know what to do, if it's worse you also know what gives. I know it's redneck, but saves hours of playing around trying this that or the other. Done it on the dyno, and in the car, most times with the trans brake.
Also if it's 3 circuit, try tooth picks in the intermediate air bleed to block them off. If that is worse, just remove the intermediate air bleed, and try again.
Obviously goal being just to know whether you need fuel there, or have too much.
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Re: Carb stumble
[Re: scarly10]
#2641703
04/05/19 08:09 PM
04/05/19 08:09 PM
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Joined: May 2005
Posts: 598 NC, USA
davenc
mopar
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mopar
Joined: May 2005
Posts: 598
NC, USA
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same clearance on the secondary AP as the primary AP? I'm at 15 thousandths at WOT Motor off, slowly open throttle to WOT and observe when the secondary shooter discharges relative to secondary throttle plate opening. Poor relationship can lead to a lean or over-rich spot; increasing primary pump discharge can cover up lean spot, or changing secondary cam or cam position to fix timing can fix lean or rich..
Last edited by davenc; 04/05/19 08:11 PM.
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Re: Carb stumble
[Re: calrobb2000]
#2641801
04/06/19 12:16 AM
04/06/19 12:16 AM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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hi
check the vacuum at idle and reinstall the correct the pri power valve .
this will add fuel before main jet and eliminate bog. You do not set power valve opening by idle vacuum. That is incorrect.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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