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Re: idle drops on stops (6 pack)
[Re: ademon]
#1630522
06/17/14 12:48 AM
06/17/14 12:48 AM
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Joined: Jan 2003
Posts: 15,569
Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,569
Omaha Ne
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Quote:
Will try the slosh tubes, and timing, funny thing is the MSD dis cap hits the intake at about 26 initial so I'll see what I can do. Funny thing is if I come to a very slow stop Idle drops only slightly, very fast stop drops a lot! Tried it without the aircleaner and it acts the same. I know the aircleaner size is not ideal but this thing lites it up and hits the rev limiter within 2 /3 seconds of nailing it with drag radials.
You're problem appears to be in the above post.
Quote:
Funny thing is if I come to a very slow stop Idle drops only slightly, very fast stop drops a lot!
Your answer is in the above quote. Hmm Slosh tubes??? Maybe, but doubtful
Float levels ??? Maybe, but only if they're to high,
Timing??? Doubtful unless the advance is loose and on the ragged edge.
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Re: idle drops on stops (6 pack)
[Re: ademon]
#1630524
06/17/14 01:45 PM
06/17/14 01:45 PM
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Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
Sxrxrnr
pro stock
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pro stock
Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
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Was all ok before installation of six pack system, or did issue occur after upgrade? Knowing would help eliminate other possibilities like timing, fuel slosh etc.
Idle mixture screws out 2 full turns sounds quite excessive,,,,possible vacuum leak somewhere?? Where are end carbs set. Have you checked butterfly location in carbs to ensure that you are not in transition circuit at idle? If so, all bets on proper idle performance could be off.
What is engine vacuum at idle?
Are you certain that power valve gasket is properly positioned,,easy to miss this,,however 2 turns out on mixture screws, I would tend to dismiss this idea, but should be checked if all else fails.
Have you tried throwing transmission into neutral before slowing down and stopping? If not try that. What happens to idle then? Could rule out fuel slosh.
Is it possible with torque flight that transmission not shifting down properly or that torque convertor is placing some temporary drag on engine. Again placing in neutral before slowing could provide troubleshooting info.
My 300b with torque flight can be a bit flaky at times when stopping car,,,also multi-carb(4 barrels) engine.
Last edited by Sxrxrnr; 06/17/14 02:03 PM.
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Re: idle drops on stops (6 pack)
[Re: ademon]
#1630525
06/18/14 12:06 AM
06/18/14 12:06 AM
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Joined: Jan 2003
Posts: 15,569
Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,569
Omaha Ne
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Quote:
That's what has me puzzled a bit. When you stop the fuel sloshes to the front of the carb away from the metering block and vent,, are the carbs going lean? Or is fuel running over the float pushing it down for a second or two overfilling the bowls? Remember these are side hung floats. I think I'm going to order the vent tubes, they will have to be trimmed to clear the float but should be better than the small brass jobs. I'm going to remove the center carb and blow everything out and maybe change the PV from 5.5 to 6.5 has a very slight hesitation once and a while at cruise when you tip in the throttle more. Thanks for the input guys.
I am not sure what the root cause is but I have set up and RUN several of the 4782 and 83 series sixpack setups without ANY ISSUE like you're describing, I currently have one on my 340 that has not been touched adjustment wise in over 15 years.
UHH More advance??? SURE CRANK IT UP TO 60 or 90 degrees initial, NOT,
Fuel sloshing??? OK Maybe if you're running a road course, NOT likely,
Flaots may be too high as they should be set to dribble, not halfway up a sight glass which was never part of this carb set up.
Your converter seems loose enough so that should not be an issue.
My guess at this point is it is between the Distributor Advance ( IE: Mechanical too loose, or the vacuum hooked up wrong.
OR
The secondary idle stops are not adjusted correctly,
OR
the secondary linkage is binding and not adjusted properly.
OR
The primary throttle cable is set too tight.
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Re: idle drops on stops (6 pack)
[Re: ademon]
#1630528
06/18/14 06:58 AM
06/18/14 06:58 AM
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Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
Sxrxrnr
pro stock
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pro stock
Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
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You say no idle mixture screws in end carbs yet your photo shows that front carb appears to have them,,,,though not factory carbs, they too have them as is stock from mopar,,,just located differently and factory plugged.
2 full turns out on mixture screws on center carb still sound suspiciously excessive, perhaps masking a vacuum leak or transition butterfly positioning issue. If you do have mixture screws in end carbs, how far out are they set?
Try throwing the car in neutral say at 50 mph. While coasting note where tach is registering. Should be your normal idle speed. Hit the brakes about as heavily as when you would when coming to a normal stop.
What does tach do then? If remains constant, would suggest that fuel slosh is not the issue. But could suggest again that transmission or convertor is causing a temporary drag on engine when coming to a normal somewhat abrupt stop.
Last edited by Sxrxrnr; 06/18/14 07:00 AM.
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Re: idle drops on stops (6 pack)
[Re: 62maxwgn]
#1630531
06/18/14 05:46 PM
06/18/14 05:46 PM
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Joined: Mar 2007
Posts: 3,291
West Coast, USA
jbc426
master
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master
Joined: Mar 2007
Posts: 3,291
West Coast, USA
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Quote:
There is no cut in stone setting for the mixture screws,back them out a couple of turns,adjust idle speed then run the screws in until engine starts to stumble,stop and back them out 1/4 turn.If turning the screws in doesn't change idle characteristics,you have problems elsewhere.
I always back them out 1/2 to 3/4 turn out after it starts to lean misfire while turning them in.
Check that your air bleeds are clear too. Remove the A/F needle and blast some carb cleaner through there.
Check your fuel pressure and try a fresh needle and seat. They can cause all kinds of strange problems. Believe it or not, my fuel system designer warned me about Holley needle and seats. He said they are batchy these days, and I had to go through 3 or 4 of them to find one that really works well for each of these side hung carbs!
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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Re: idle drops on stops (6 pack)
[Re: ademon]
#1630532
06/18/14 06:41 PM
06/18/14 06:41 PM
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Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
Sxrxrnr
pro stock
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pro stock
Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
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Quote:
Outboards have no mixture tuning provisions. I'm going to try to check it over in the next few days. Is just short of two turns out that much? Most say to start with the screws 1.5 turns out anyway.
Sorry,,,,looking at photo on side of front carb metering block appeared to be mixture screw as on certain carbs. When I blew up photo, did not appear to be so.
John's comments on needle/seats sounds quite reasonable,,,,still however would try throwing in neutral at cruising speed and see what tach does while coasting down to a stop,,,as a backup to John's theory.
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Re: idle drops on stops (6 pack)
[Re: ademon]
#1630535
07/05/14 07:23 PM
07/05/14 07:23 PM
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Joined: Sep 2004
Posts: 6,906
IL, Aurora
ademon
OP
master
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OP
master
Joined: Sep 2004
Posts: 6,906
IL, Aurora
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Haven't had time to drive it much since i turned out the screws to about 2 3/4", so today i drove it a bit and wanted it to idle about 900 instead of the 1,000 and it started to drop coming to stops again. So figured maybe the outer throttle plates need to be opened that made it worse so went back the other way and closed them a little more than before and opened the center carb more. That made it idle the best. I did drop the fuel level back to the bottom of the site plugs just dribbling out when lightly rocking the fender.
Bottom line is this setup on my SB looks like it has to idle at 1,000rpm, I'll try to play a little with the idle mixture screws in the future a see what happens but it drives nice now! has a little hesitation on tip in when at a steady cruise and squeezing the throttle sometimes, may need a bigger squirter in the center than the 31.
Last edited by ademon; 07/05/14 07:27 PM.
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and used one that was harder to get air to move through but that did nothing. Still a bit to do.. when i pulled into the drive and opened the hood there was some fuel dribbling out of one end carbs squirter so hopefully that will go away when i drop the floats back to the bottom of the sight holes!