Re: Carburetor tuning with a wideband A/F guage.
[Re: mopfried]
#1564806
01/18/14 02:56 AM
01/18/14 02:56 AM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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I drove the car last week. There was no detonation at all. I'll admit that the weather was in the 50s but at 10.07 to one and a pretty big cam it should do fine. Reading the plugs has been mentioned before but I'm not sure what to do. My understanding is that they have to be removed immediately after a WOT run. I have burned my hands trying this before with the tight clearance this car has. I was hoping that the Air/Fuel guage would be a good way to avoid burn scars! I have a wide assortment of jets and power valves. Currently I believe I have #86 primaries and #94 secondaries. The original jetting was 85/93. My plugs are new. The plug wires have about 100 miles on them. cap and rotor are fresh too. Misfire? I hope not since everything has been replaced.
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Re: Carburetor tuning with a wideband A/F guage.
[Re: Kern Dog]
#1564807
01/18/14 05:18 AM
01/18/14 05:18 AM
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Joined: Aug 2003
Posts: 43,185 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,185
Bend,OR USA
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I ran my duster 518 motor at or above 14.3 to 15.2 AFR at part throttle up here at 3500 Ft above sea level on my Innovate LM1 with the LC1 conversiion to dual wide band I did run a cooler plug than most, Autolites AR3911 and AR3910, I also ran both the Champion RC12YC and the RC9YC, the motor ran well with all of them I had it at between 12.8 to 13.5 AFR at WOT with the six pak and the single 1050 CFM Dominator carbs. I tested, I had issues early on with inadequate fuel supply(10 micron fuel filter between the tank and the pump )the motor would leave the line at 14.2 AFR and cross the finish line at Bakersfeild(in really bad weather conditions) at 15.8 I got lucky and didn't hurt it, don't try that yourself Tune it until you like it, lean it down until it feels bad, richen it up until it feels bad again, find the sweet spot you like Then look closley at the plugs for the part throttle driving and put in several new plugs when you go test the WOT runs IHTHs
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Carburetor tuning with a wideband A/F guage.
[Re: Kern Dog]
#1564808
01/18/14 11:37 AM
01/18/14 11:37 AM
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Joined: Jan 2003
Posts: 5,443 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,443
Indiana
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Tune the carb starting at the idle and then work your way up to WOT. If you jump around on your tuning sequence, it will take you allot longer to make progress. At idle: if the engine makes best vacuum = best a/f for your engine. This may differ than one of ours. Off Idle: Idle Air Bleeds/ Idle Feed Restricters will combine to give you the A/F that you are looking for. IAB's make tuning this rpm range a quicker process. Tune the off idle/low rpm cruising speeds to around 13 and see how it feels. Then lean it out to around 14 and see how it feels. Choose the a/f that is not lean enough to cause deination or heating up issues. Accel to medium acceleration from cruising speed: main jets/power valve/power valve Restricters: tune these to keep your accel richer than your cruise but leaner than your WOT. After the rest has been tuned, then use your rear jets/rear main air bleeds to tweak in your WOT a/f to around 12.5 for starters.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Carburetor tuning with a wideband A/F guage.
[Re: Kern Dog]
#1564809
01/18/14 02:32 PM
01/18/14 02:32 PM
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Joined: Jan 2003
Posts: 12,085 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,085
Benton, IL.
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In order to adjust the different circuits of a carb, you have to understand the different circuits AND how they overlap and transition to each other. Do you have Emanuel's Holley book? Some sort of reference and instruction material is essential to get started. For instance, does your car cruise on the idle circuit or the main circuit? You need to know how to determine that so that you know which circuit to adjust. I will say this; set the idle mix where the engine likes it best, not by a target ratio. I have one engine that likes 13.6 for idle and one that likes 14.1. If you have 100% gasoline, the cruise will like about 14.7 which is stoich. But if you have 10% ethanol, that target will change. My engine's preferred WOT ratio will usually be somewhere between 12.5 and 13.2 depending. You'll also need jets, bleeds, power valves, small drill bits, maybe some wires and a lot of time to experiment. Trial and error is the path to success for you. We can give you some starting points or tell you what worked for us, but only you can find what is best for your particular combo.
Master, again and still
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Re: Carburetor tuning with a wideband A/F guage.
[Re: DaveRS23]
#1564810
01/18/14 04:13 PM
01/18/14 04:13 PM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Thanks for the suggestions so far! I forgot to mention that here in CA the gas pumps have a sticker that reads "Up to 10% Ethanol" yet testing has found an average of 6% is common across the state. It makes sense that each car may respond differently. The compression, intake port design, exhaust system, camshaft, carburetor and ignition of each car combine to be unique to any car screwed together 40 years after Ma Mopar had her hands on it! I have a Holley book to peruse. I'll take a gander once I get out to the shop. Thanks again.
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Re: Carburetor tuning with a wideband A/F guage.
[Re: Kern Dog]
#1564811
01/18/14 04:31 PM
01/18/14 04:31 PM
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Joined: Jan 2003
Posts: 5,443 Indiana
YO7_A66
master
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master
Joined: Jan 2003
Posts: 5,443
Indiana
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One of the toughest parts is figuring out which circuit you are on while cruising (let's say 30_70mph or so). As mentioned, once you know which circuit you are on, then you take allot of the guess work out of the tuning. When you are out cruising, take notes of the a/f reading at different steady cruising speeds (ref: 30/40/50/60/70mph) then when you make a tuning change, write down the new a/f reading at these same speeds. This will show you exactly where your change made a difference good or bad.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
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Re: Carburetor tuning with a wideband A/F guage.
[Re: Supercuda]
#1564815
01/18/14 10:42 PM
01/18/14 10:42 PM
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Joined: Jan 2003
Posts: 12,085 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,085
Benton, IL.
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14.7 is the one number the OP can target and be fine, not necessarily perfect, but fine. We can get into a lot more intricacies of this, but it would simply be over the OPs head. I readily admit that the 14.7 target is not likely optimum, but the OP doesn't really have the abilities to set the cruise any finer. The idle and WOT, he can. Rather than limiting yourself to criticism, why don't you suggest the best process for a carb noob to set his cruise ratio. He has no tools, parts, or recording ability. At this point, anything more than I suggested will bury him. I was only trying to help a noob get to an acceptable point, not give him an engineering lecture.
Master, again and still
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Re: Carburetor tuning with a wideband A/F guage.
[Re: Cab_Burge]
#1564819
01/19/14 03:30 AM
01/19/14 03:30 AM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Reading the plugs is often mentioned. I have never done this. I hate to sound like a newbie but in a 440 B body with 2" headers and power steering, how is this done without burning a persons hands? Every time I have changed the plugs I wait until the headers cool down. I'm a Carpenter by trade and obviously need my hands for work. Isn't the procedure to run the car hard at WOT then shut down and pull the plugs immediately?
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Re: Carburetor tuning with a wideband A/F guage.
[Re: Kern Dog]
#1564820
01/19/14 04:07 AM
01/19/14 04:07 AM
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Joined: Nov 2003
Posts: 1,881 Pittsburgh,PA
RTSrunner
top fuel
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top fuel
Joined: Nov 2003
Posts: 1,881
Pittsburgh,PA
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Quote:
Reading the plugs is often mentioned. I have never done this. I hate to sound like a newbie but in a 440 B body with 2" headers and power steering, how is this done without burning a persons hands? Every time I have changed the plugs I wait until the headers cool down. I'm a Carpenter by trade and obviously need my hands for work. Isn't the procedure to run the car hard at WOT then shut down and pull the plugs immediately?
After your WOT run you can let the engine/headers cool before removing the plugs. The plug coloring will not change while the engine is off.
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