Re: 365" 6 pack, 4 rear plugs white.
[Re: ademon]
#2263921
03/05/17 08:37 PM
03/05/17 08:37 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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vac leak possibly? The meter is only gonna show the overall AF ratio. I have a "colortune" which would be good for diagnosing that, a special spark plug that lets you see the color of the flame in the cyl as it is running, you want a nice blue like a bunsen burner in a high school chem class, not red and not yellow. EDIT What I would do is drill into the ex manifolds at the offending cyls & take an AF ratio with an LM-1 & you'd cap the mani holes back shut when done. It'd take some doing but I'd wanna know (& get it right if need be).
Last edited by RapidRobert; 03/05/17 08:41 PM.
live every 24 hour block of time like it's your last day on earth
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Re: 365" 6 pack, 4 rear plugs white.
[Re: ademon]
#2264465
03/06/17 07:17 PM
03/06/17 07:17 PM
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Joined: Jul 2011
Posts: 960 Chicago
PurpleBeeper
super stock
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super stock
Joined: Jul 2011
Posts: 960
Chicago
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Rapid has a good point. A vacuum leak in the back half of the manifold (or rear carb) would do that. You could try the old "carb cleaner everywhere that could leak and listen for an idle change" trick too.
If there aren't any leaks, then maybe you need to fatten up the rear carb's fuel mixture? Just a thought.
70 Roadrunner convt. street car
440+6, NOS, 4-spd, SS springs
'96 Mustang GT convt. street car
'04 4.6 SOHC, NOS, auto, lowered
"Officer, that button is for short on-ramps"
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Re: 365" 6 pack, 4 rear plugs white.
[Re: ademon]
#2264526
03/06/17 09:14 PM
03/06/17 09:14 PM
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Joined: Aug 2003
Posts: 43,257 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,257
Bend,OR USA
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You need to keep in mind that the stock type Eddy SB six pack intake is a dual plane type intake and you may need to stagger jet the carbs. you have to balance the fuel distribution at part throttle and on the transition circuit when cruising at light part throttle cruise settings. Your AFR reading are right what I shoot for on my cars Are any of the spark plugs shiny? If so that makes me think intake manifold leak allowing oil to be sucked up into it You might want to install the next colder heat range spark plugs in those holes if you don't find and fix a intake manifold vacuum leak first Let us know what you find
Last edited by Cab_Burge; 03/06/17 09:15 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 365" 6 pack, 4 rear plugs white.
[Re: ademon]
#2264920
03/07/17 03:02 PM
03/07/17 03:02 PM
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Joined: Jan 2003
Posts: 15,469 Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,469
Omaha Ne
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Something obviously is leaning the rear cylinders out. After reading and thinking about it, 1. My first thought was a power brake booster leaking but being a dual plane intake its not likely to affect all 4 cylinders. One could try removing both secondary carbs, blocking them off and run it just off the center to see if the problem improves. Depending on those results I would proceed to pull the intake, check the sealing on the rear ports and have the intake checked for internal leaks. Keep us posted
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Re: 365" 6 pack, 4 rear plugs white.
[Re: ademon]
#2265202
03/07/17 11:12 PM
03/07/17 11:12 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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What I would do is put the old plugs back in right now (dont start it on the new plugs) & go out on the interstate & pull over & put the new plugs back in and disable the accelerator pump & ease back onto the hiway & go ten miles or so at the speed limit so you are on the main metering system with no corruption from the AP & hopefully not the transition circuit (I ain't a carb guru) & at the right time cut the ign & take you foot off of the gas at the same time & coast to the side of the road & pull some plugs & see what they look like to get a valid read on what the main metering system is doing for AF ratio in the different cylinders. EDIT may need to go 15 miles, todays unleaded gas shows less color.
Last edited by RapidRobert; 03/07/17 11:35 PM.
live every 24 hour block of time like it's your last day on earth
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Re: 365" 6 pack, 4 rear plugs white.
[Re: ademon]
#2265219
03/07/17 11:43 PM
03/07/17 11:43 PM
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Joined: Jan 2003
Posts: 15,469 Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,469
Omaha Ne
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Reading your latest post would indicate that the front carb was most likely contributing excess fuel to the front cylinders thereby en-richening their mixture. If that in fact is true I would also expect to see have seen some difficultly in setting the mixture screws. I have been running the mechanical six packs on various motors for about 40 years and will offer the following: The secondary carbs are just that, secondary. Think of a 4 barrel with an extra set of secondaries. The main idle and low speed operation is mainly controlled by the primary carburetor. A very small amount of fuel is contributed by the secondaries during low speed / idle mainly to keep the fuel from going stale in the bowls. I have always set the the secondaries idle screw about 1/8 to 1/4 turn open on both carbs trying to egt them as equally set as possible. I have then used the center carb for the rest of the low speed /idle operation. With a bumpier cam and an automatic they can be opened a bit more if needed to get the primary blades in the correct relationship to the idle, off idle transition. Once the secondary adjustment if equalized the linkage should "SLIP" into both carbs with no pressure. keep us posted
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Re: 365" 6 pack, 4 rear plugs white.
[Re: TJP]
#2265262
03/08/17 12:27 AM
03/08/17 12:27 AM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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What TJP said sounds right (I missed it), get the carbs straightened out.
live every 24 hour block of time like it's your last day on earth
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