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Discussion Starter #1
I decided to use an A/F Ratio gauge to help tune up the dual quad on my 289. I have set the idle and fuel level on the carbs, but I figure if I'm going to do this, better get it dialed in. I read a few articles online on getting this done, and one of the better ones I read was this one:


I don't have all the issues he had regarding manifold and leaky intake gaskets, but once he starts working on the carburetors, he provides a lot of detail.

I'm running a pair of QuickFuel 425 Slayer carburetors that have been setup at the factory specifically for a dual quad system.

For the AFR gauge, I went with the Glowshift Wideband system. I won't be permanently installing the gauge in my vehicle, but I will have my co-pilot, my daughter, helping me out when it comes to getting the numbers when on the road. The reason I went with the Glowshift AFR system instead of the highly recommended AEM is I have seen on Amazon that out of the last 39 reviews for the AEM since January 2020, 33 of them were negative due to being delivered with bad O2 sensors. Another VMF'r advised me that his AEM came with a Bosch sensor and did my Glowshift, so I may still get stuck with a bad sensor. We'll see.

Anyway, this is what was delivered. The Glowshift AFR gauge, wiring, O2 bung with plug, Bosch sensor, all kinds of wiring, and instructions.

755018
 

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Discussion Starter #2
The next thing to do was to try and figure out where I was going to put the O2 bung and sensor. I know to keep it above horizontal to ensure no moisture collects on it, and far enough downstream in the exhaust system to ensure it gets exhaust gases from all four cylinders from the right bank. Now, I have a pair of $39 headers that have been on this car since 1980, and the collector is just too short. The O2 sensor would be only 4" away from where the pipes from the head meet up in the collector. I'm figuring the O2 sensor will only be getting exhaust gas from one, maybe two cylinders, and that's it. So further downstream I decided to go down the exhaust pipe. I ended up deciding to go right before one of the bends in the exhaust, and drilled a 5/8" hole to fit the sensor. Took the exhaust and bung to my reliable, local machinist, and he'll go ahead and drill the hole a little larger to allow the inner lip of the O2 bung to sit inside the exhaust pipe, and weld it in place. This is where I'm at now...just waiting to go pick it up when I get the call.

755022
 

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I’ll be doing the same thing, but I have shoulder surgery in 3 weeks, so might be this fall or next spring. It’s a handshaker and it’s my right shoulder, so I’m afraid the car will be parked for awhile :confused:
Definitely curious to see what you find out!!
 

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Discussion Starter #4
The O2 bung has been installed, and the exhaust has been partially restored. I'll get the header bolted back onto the head and the exhaust pipe back onto the collector next, and then it will be time to start routing the wiring into the inside of the car and see what we've got going on. Here's the bung welded on - the background is the floor of my garage AKA dirt and rocks.

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I just installed an Innovate Motorsports air fuel guage just about a week ago. I have my O2 sensor installed on the driver's side in about the same place you describe. Innovate says to mount the sensor around 21 inches downstream of the exhaust. I am running heddman shorty headers. Put the bung right after the pipe makes its curve to run towards the back of the car. Seems to work well. Tuning by air fuel ratio is so easy. I was able to tell that I needed to go up a jet size on my primaries. This also improved my idle. Before I was out almost 2.5 turns on the idle. Now I am right around 1.75 . Also allowed me to diagnosis an issue with my pcv. Which also help my idle as well. Think I am going to order one of those tunable pcv valves. I am interested to see how that affects idle and air fuel ratio.
 

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Discussion Starter #6
This project has been put on hold for a few days. I've been working on my daughter's 98 Dodge Dakota, and replacing the lower ball joints. Then I found the sway bar links, the upper ball joints, and then tie rods are also all shot. Of course, the ball joints are riveted on, so that's been a fun challenge getting the old ones off. One side is completely dismantled and waiting on parts to arrive.
 

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I just installed an Innovate Motorsports air fuel guage just about a week ago. I have my O2 sensor installed on the driver's side in about the same place you describe. Innovate says to mount the sensor around 21 inches downstream of the exhaust. I am running heddman shorty headers. Put the bung right after the pipe makes its curve to run towards the back of the car. Seems to work well. Tuning by air fuel ratio is so easy. I was able to tell that I needed to go up a jet size on my primaries. This also improved my idle. Before I was out almost 2.5 turns on the idle. Now I am right around 1.75 . Also allowed me to diagnosis an issue with my pcv. Which also help my idle as well. Think I am going to order one of those tunable pcv valves. I am interested to see how that affects idle and air fuel ratio.
Tell me more about your set up? You went up in primary jet and your idle got better? What kind of carb are you working on?
 

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I was going to install the Auto Meter 4379 AFR gauge as it shows good reviews compared to the AEM and Innovative gauges. But like you, my daughters car decided to not blow cold A/C air. So working on that and it might be expensive. So my car has to wait for new parts since its not a daily driver. :) Let us know how the gauge works when you finally are able to use it.
 

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I just received my Speedhut AFR gauge, it matches the Speedhuts it my dash. I purchased a beat up original ashtray to paint match to my dash and mount it there. I am installing it to help with tuning also.
Rusty
 

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Tell me more about your set up? You went up in primary jet and your idle got better? What kind of carb are you working on?
I am using a summit 600 cfm vacuum secondary carb. The improvement in my idle was definitely unexpected. I was actually just trying to fatten up my cruise AF ratio a little bit. I know that on the Summit carbs the jets are on the bottom of the bowel and the fuel has to go through them before they get to the idle circuit.
 

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Discussion Starter #11
Time to get caught up.

After getting my daughter's truck back on the road, I returned to my AFR gauge project. In not thinking ahead, I had the O2 sensor bung welded onto the inside of the exhaust, towards the transmission. I looked around for a place where I could route the wire from the O2 sensor into the cab of the car without having to drill a huge hole. I went online to get some ideas, and found an article where someone hooked up an AFR gauge in a Fairlane and ran the wiring through the floor drain plug! Now that's an excellent idea, but the drain plugs on my 65 are on the otherside of the exhaust where I welded the bung. I HATE when I do that! So I took the wire from the O2 sensor, routed it over the exhaust, around the parking brake spring, to the rear of the frame rail, and up into the floor drain plug.

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One thing I don't like about these O2 sensors - why in the heck is the plastic connector so freakin' huge?

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Anyways, I ran the wiring from the O2 sensor into the separate controller before it goes the AFR gauge. There is also another wiring harness that supplies switched and unswitched power, along with the ground and if you want, a wire to go to the headlight switch so when the dash lights are turned on, the gauge will dim. I moved my fuse panel from its stock location to a homemade panel inside the glovebox. I have one fuse block for switched power, and one fuse panel for unswitched power. I just ran the wiring down inside the kick panel to the front floor. Here's what the tangled mess of wiring looks like on the front floor of my car:

756294


Got it all hooked up and have the gauge sitting inside the cup holder on my aftermarket console.

756295
 

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Discussion Starter #12
After I go everything all hooked up, I fired up the beast. After the O2 sensor warmed up, the needle went off the scale showing that at idle was really lean. As it was warming up, I could hear that my exhaust wasn't sounding quite right. Started checking things out, and found the bolts were loose at the header collector. After a couple of heat/cool cycles, things had backed off a bit, and I'm sure there was a bunch of fresh air entering the exhaust and playing all kinds of goofy games with the O2 sensor. I tightened the bolts back up and ran my hands around the gasket area to make sure I couldn't feel anymore leaks. None! Also checked the header flange at the head just to make sure everything was tight there, and good to go.

Started the engine again and got it warmed up. I was showing around 17:1 at idle, which is really lean. So I started turning out the idle mixture screws to add more fuel to the idle. One thing I noticed....just turning the screws 1/8th of a turn makes a big difference in the A/F ratio. So I would do 1/4 turns at a time until I got close to 14:1, and then did 1/8 of turn each time after that. Once I got to 14:1, I figured I was good to go. After I shut it down, I checked my idle mixture screws and they were out 2 3/4 turns. Wow...never had to turn out mixture screws that far. I also noticed that my idle speed screw was having no effect on the idle. Idle was at 1200/1250 rpm, which is a bit higher than I like, and with the idle speed screw backed all the way out, the RPMs wouldn't drop. Okay...lots of air getting in somewhere.

I checked around all the vacuum ports, PCV, base gasket, etc, and just wasn't finding where all the air was coming from. I sprayed with carb cleaner and no change in the idle. So I did a little bit more research, and narrowed it down the the idle air bleeds inside the carbs. From the factory, the idle air bleeds are a size 70 in the primaries and 39 in the secondaries. I did some switching around of the air bleeds and moved the 39's to the primaries. Big difference! Now the carbs were running too rich. So I adjusted the idle mixture by turning in the screws enough to get back to 14:1, and the idle speed screw now had an effect when turned. After changing the air bleeds, my RPM went from 1200 to 500. My engine seems to like to idle around 900 - 1000 rpm, so once I get the mixture figured out, I set the idle at 1000 rpm.

This is where I'm at now. I've ordered some more air bleeds for these carbs because going from 70 to 39 was a big drop. Just about everything I've read about tuning these carbs recommends not such drastic changes at once, which is what I've done. I'll wait until the new bleeds come in, and I'll start from the beginning and go from there.
 

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I was running really lean as well. Running like 2.5 turns out. I bumped up the primary jet size to fix my lean cruise and my idle got rich. I was able to turn them down to 1.5. I have the transfer slots like little squares adjust idle speed with my secondaries. This is on a summit carburetor. Not sure if the info will help on yours but changing primary jets fixed the problem for me.
 

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Leefred, what kind of carb are you working on??
I don't mean to step on his thread, but, he mentioned this in opening "I'm running a pair of QuickFuel 425 Slayer carburetors that have been setup at the factory specifically for a dual quad system."
 

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850 cfm of carbs on a 289 seems like much, but who knows till we get more engine info.
 

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Discussion Starter #18
850 cfm of carbs on a 289 seems like much, but who knows till we get more engine info.
289 with TW 170 heads, Pertronix II distributor, Cyclone long tube headers, Blue Thunder intake that I port matched to the heads. The cam is a Comp Cams XE262-H. Stock crankshaft with HiPo 289 rods and SpeedPro flat top pistons. Running a close ratio Toploader and 3.55 gears.

My previous setup with the dual quad was 990 cfm of carburetor and had pretty good power and good MPG. That one I tuned by ear and a vacuum gauge, and think I did good with it. Both setups are run progressively with the secondary carb starting to open around 70mph in 4th gear.
 

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Great thread! Learning a lot here. Now that I've pretty much learned to tune the 'old school way' with carbs mixtures and timing I am installing one of these AFRs when I have an exhaust guy redo my entire exhaust. Single to dual. I'll only be connecting to it at tuning time. Not bringing it into the car permanently.

Only question is how do you decide which bank to use? Passenger or driver? Is it just random...as in you pick one or the other?
 

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Discussion Starter #20
Only question is how do you decide which bank to use? Passenger or driver? Is it just random...as in you pick one or the other?
I've noticed that a lot of folks with V8's use the passenger side bank. I don't know if it's because there's less stuff on that side, such as clutch linkage, steering components, etc. Never saw a reason why the passenger side is used more often. From what I understand, either side is good if not using dual O2 sensors.
 
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