UPDATE: After moving the pri jets to 71, the lean miss on light throttle is much better. Unfortunately it will still occur when hitting 10" vacuum, with the AFR in the high 15's, low 16's. I am going to have to go back to 72s. This is the jet I had previously determined to be the smallest I could use on the primaries, and in some ways it is reassuring that I came back to the same place.

With the HSAB, .027 didn't help much, so I increased some more to .029. It is better now, but the AFR on WOT still goes rich into the low 11's. Next step will be .031, and I suspect I may end back at the factory size of .033 when it is all said and done.

My low speed cruise (45MPH) was in the mid-13s, so I upped the IAB from .065 to .067 which seems to have helped, with numbers now in the high 13 to mid 14 range. I don't have a lot of flat roads around me so it is a little hard to be precise.

On the highway, the AFR was not jumping around like it has in the past which is interesting since I'm not sure why that has changed given that I am slowly working back towards my old settings. The AFR was in the mid-13s which is the best it has been in a long time.

In general, it seems I have finally made some progress. On the negative side, it seems that I have a light throttle miss that does not appear to be AFR related. I don't know if it was always there but I couldn't notice it because of how the motor was running with other issues. It doesn't occur under WOT. I long time ago I suspected a vacuum leak (at the manifold) but I could never find anything. The vacuum advance is not hooked up so I know it is not over-advanced.

I did not realize that you disconnected the secondaries. Now I understand the HSAB changes. Nice job!! Even if you end up back at the original .033's, you would have never known what the lean limit was without trying.

High 13's to mid 14's is excellent in my book. I have been told that I may not find the perfect setup on the primary side only (with seconds disconnected), but I hope to see how close you can get yours. You are definately getting closer with each change. That is what I love about the A/F gauges. You can see where you were and where you are now.

I am going to test a lower float setting on the primary side to see if I can lean out my new 64 jets above 55mph. I have now dipped down to 13.4 at 60mph (.039 HSAB's). My 62 main jets gave me 14.0 at 60mph with the .039 HSAB's, and I want to see if I can get into the upper 13's with the front float change. If not, I might drill out some old bleeds to make (2) .042" HSAB's just for the front to see if that gets me back on track.

I am going to try and richen up my 50-WOT A/F which is now 12.8 (D) and 13.0 (P) down to 12.5/12.6 with just a rear float change. I hope to test this out this coming week.

Please keep us updated on your progress!!

"That is what I love about the A/F gauges. You can see where you were and where you are now."

I agree. I only have one though, and given my light throttle miss, I am now wondering if the other bank is significantly different. At light load and light cruise (perhaps 40-45MPH) I don't notice the miss. Going up a hill under the same conditions will show it though, even though the AFR is generally in the 14s (when I feel the miss I also see the AFR jump lean, as you would expect). First up, I think I will replace the plugs since perhaps the really rich WOT trials have fouled them a little.

"drill out some old bleeds to make (2) .042" HSAB's just for the front to see if that gets me back on track."

You probably know this but be very careful drilling jets. The flow is a function of the hole diameter and the length of the restriction. When you drill a jet, the hole gets bigger, but the length also increases. For a while I was trying to increase my PCVR by drilling some blanks but I always ended up leaner than the biggest QFT jet I had purchased. Finally it dawned on me that I had stumbled into this trap.

Good point on the air bleeds. I will not drill any of my existing pieces.

I have seen members on board say that buying a sensor for each side is stupid, dumb, waste of money, etc.. But I know first hand that "on my motor", there is a difference from side to side.
When I have the car in N and I am balancing out the metering screws, I can move the drivers side main metering screw and watch the P side O/2 gauge move. I have a dual plane intake, so that makes sense. So I have to take my time and go side to side to get the result that I am after for both sides. When I added the second sensor, the cruise was real close side to side and the WOT was off by .5/.6 side to side. Now I have the idle, cruise, and the WOT within .2 side to side.

I would suggest that you move the sensor to the other side to check your thoughts. You may be correct.

I separated my exhaust (straight thru each side) so that I could run the dual sensors without the exhaust contaminating the other sensor. I am glad that I did because I can set here at my keyboard and smile when I see someone say that the second sensor is worthless, especially on a dual plane intake.

Lowering the front float to the bottom of the sight glass helped lean out the 60mph A/F by .2. Raising the rear float to the middle of the sight glass helped richen the 50-WOT by .2 also.
Last year my 30-70mph A/F readings were 14.0-14.6 and I was not running vacuum advance.
After this last test, I am now:
Idle in D: 13.6-13.8
40mph:14.0
50mph: 13.8
55mph: 13.6
60mph: 13.6
4000rpms (apx 75mph): 13.2
50mph to WOT: 12.8(D) 12.6(P)
You can see by the 4000rpm A/F reading that my .039" HSAB's are not leaning out the main circuit. So this setup should be good.
So this year while running with vacuum advance, my cruising range is apx 13.4-14.0. I feel surging aroung 14.4-14.6 or so with the VA hooked up. So this setup gives me some room before the surging starts. The car feels strong at cruising speeds to any accel. I am no longer leaning out into the 15's and it stays no leaner than 14.0.
I might try raising my rear float to about the 3/4 mark to see if I can richen up my 50-WOT readings to around the 12.5-12.6 range on both sides. 3/4 up is all the higher I want to raise the float to allow fuel expansion during heat soak and not have the fuel expand and want to come out of the boosters when shut off.
I have found that the floats are a real quick external adjustment to get about .3-.4 change in the A/F readings. I would like to find a happy medium with the internal parts of the carb so that all I need to do year around is tweak the float level as the outside temps rise/lower.

EDIT:
I have decided to keep the rear fuel level to the middle or below, so this means rejetting the secondaries. 78/78 rear jets gave me 12.0 (D) and 12.4 (P). 76/74 rear jets are currently giving me 12.8 (D) and 12.6 (P). I am going to stagger the rear jetting slightly more and test 78/74. I am thinking that since I am running a dual plane intake, that the 78's on the drivers side will richen the drivers side 12.8 reading and hopefully help richen the passenger side slightly too. The larger jet will allow me to keep my rear fuel level under the half way mark which allows more room for the fuel to expand during shut down.

EDIT:
The gas stations are allowed to start selling the Winter blend this coming Saturday, September 15. What does this do to our current A/F ratios, if any?

Previous results with 64 p jets and 76 (D) and 74 (P) secondary jets:
""Idle in D: 13.6-13.8
40mph:14.0
50mph: 13.8
55mph: 13.6
60mph: 13.6
4000rpms (apx 75mph): 13.2
50mph to WOT: 12.8(D) 12.6(P)""
--------------------------------------------

I could not stand it that my 50mph+ A/F went as rich as shown. So I decided to drop my primary jetting from 64's to 63's. I knew that this would cause my WOT numbers to go lean so I swapped my rear jetting to 78/76.
My new results in cooler weather (53-59 deg.):

Idle in D: 13.6-14.0
40mph: 14.0
50mph: 14.4
55mph: 14.2
60mph: 14.2
4000rpms (apx 75mph): 13.8/14.0
50mph to WOT: 12.8(D) 12.8(P)

As you can see, the main jet swap from 64's to 63's brought my 50mph+ numbers back up about .6-.8 in the cooler weather. This is where I want to be for cruising.
Now I have a question about the secondary HSAB's and their function.
I would love to just swap out something external when the outside temps go up and down. I am still very close on my 50-WOT A/F numbers (12.8's & aiming for 12.5-12.6). My current stagger jetting on the rear looks good but instead of opening up the rear bowl again to add 2 more jet sizes per side, what about swapping my SECONDARY HSAB's ONLY from the current .039's to .036's?
Would this change mess with my 50mph+ A/F cruising numbers?
I would love to just swap out secondary HSAB's as the temps go up/down since they are so easy to get too.
What do you think about this change and it's affect on my cruising A/F?

Thanks

"Now I have a question about the secondary HSAB's and their function.
I would love to just swap out something external when the outside temps go up and down."

First, I would not expect the secondary HSABs to have any effect on the 50MPH cruise AFR since I can't imagine that the secondaries are operating on the main circuit at that point.

With respect to their function, my understanding is that the HSABs are tightly coupled with the boosters. The booster design will produce a particular "signal" for the main circuit. The booster signal by itself is non-linear though, with a non-proportional increase with air flow. The high speed air bleed acts as a "trim" for that signal. When the booster and air bleed are properly matched, then the AFR curve should be linear with air flow. If the air bleed is too small, then not enough booster signal is trimmed, and the result is more fuel flow, and as seen in my recent experiments, a AFR that gets richer with RPM. If the air bleed is too big, then the opposite happens, with a AFR that gets leaner with RPM. What I don't know is the exact sensitivity to the bleed size, and whether the secondaries operate in a narrow enough region to allow a measure of variation in bleed size around the ideal point. On a race motor that operates in a somewhat narrow region (say 5K-7K) the bleed might be an easy way to make an external adjustment. On a street motor, the situation may be different. Worse case, you will need to experiment. However, some sort of data logging would really be helpful with something like this.

All that said, I thought you were a proponent of using the float level to fine tune the AFR via external means. That sounds like a good idea to me, particularly on the secondaries. Are you concerned that does not give enough adjustability?

""All that said, I thought you were a proponent of using the float level to fine tune the AFR via external means. That sounds like a good idea to me, particularly on the secondaries. Are you concerned that does not give enough adjustability?
""

I do like to use the floats as an external fine tune, but my rear float is already at the halfway mark. At that level, I know that I can get +/- .2 but I am not sure about taking it up higher than that mark. I think that I need a few ticks richer before I can be comfortable with that float height.
I might try the smaller rear HSAB just to see and report back. I know for a fact that making this same HSAB swap on the primary side changes the A/F a bunch. But as you wrote, the seconds are not active at this rpm level but I am not sure that if there is any residual affects on the main circuit.

Thank you for the reply. That explains it very well.

""I would not expect the secondary HSABs to have any effect on the 50MPH cruise AFR since I can't imagine that the secondaries are operating on the main circuit at that point.""

You are EXACLTY correct. I swapped the rear .039" HSAB's for .036" HSAB's and went for a drive. No other changes and the outside temp was 61 degrees vs 59 degrees yesterday.
Yesterday I showed my 50mph to WOT as 12.8 (D) and 12.8 (P)sides. Today I tested this three times and found 12.6/12.6, 12.6/12.4,& another 12.6/12.4. I have hit the 12.5 mark!! The car felt strong and I am happy with this.
My 40mph, 50mph, and my 60mph cruise A/F numbers WERE NOT AFFECTED by the secondary HSAB swap.
I had the exact same numbers as yesterday on cruise!!

Thank you Dave!!!!!

Note: My float levels are right at the mid line on the bowls. This allows me some tweaking to lean it out. Since I drive in 50-95 degree weather, this gives me some room on both the main and the secondary float adjustments for leaning it out in warmer temps. Now that I know that I can gain/lose .2-.4 on the secondary WOT reading with the HSAB swap, this is another external (quick) change that I can make during a normal driving year.
The metering screws handle the idle to off idle A/F changes and the IAB's handle the transition circtuit changes, I need to test to see if my existing internal carb setup is good. I am at 63's for front jets, .039" HSAB's up front, 9.5 HFPV/.071 PVCR's, .065 IAB's (all), .033" IFR's (all), 78 rear drivers and 76 rear passenger jets with the .036" HSAB's in the rear.
Time will tell.

"Today I tested this three times and found 12.6/12.6, 12.6/12.4,& another 12.6/12.4. I have hit the 12.5 mark!! The car felt strong and I am happy with this."

Excellent! Were you able to observe the AFR over a range of RPM? Notice any difference between the low end of the range and the top?

I see you list .071 PCVRs; did you purchase those or make them?

I bumped up my main jets from 71 to 72, and my light throttle stab AFR is now much better, so at least that is one improvement. However, my WOT is still way over rich (low 11s) and I tried .031 and .033 HSABs. Given that .033 HSAB is factory I am thinking I was wrong to assume that my over rich mixture was due to using the very small HSABs. Something else appears to be going on. I plan on going back to my .061 PCVRs and see what happens. Unfortunately rain today so it will need to wait for another day.

""Were you able to observe the AFR over a range of RPM? Notice any difference between the low end of the range and the top?

I watched it from in D idle, all the way to WOT shift point. The ONLY change was the WOT A/F went richer as noted.

""I see you list .071 PCVRs; did you purchase those or make them?""
I bought them from QF. I have four to chose from and those are the richest that I have. Since my cruise is 14.0-14.2, I tested with all four sets and found that these had the best "seat of the pants" feel from cruise to heavy accel.


""I bumped up my main jets from 71 to 72, and my light throttle stab AFR is now much better, so at least that is one improvement.""

I found the biggest improvement in cruise to light throttle accel when I swapped the 62 jets for the 64's. The 62's were showing a lean spike into the 15's from cruise to light accel. Then when the 64's were installed, the light accel stayed right around my cruise A/F (13.8-14.0). That felt good but the 64's were too rich on cruise. So when I moved the mains back down to 63's, my 50mph+ cruise is now 14-14.2 again but the cruise to light accel is now mid to high 14's which I can live with.
I am trying to come up with a way to richen this cruise to light throttle back up (like the 64 mains showed) but without richening my 50mph +. The only guess that I have is with larger PVCR's which I think there is only one more step richer than the .071's from QF (.073's). I tried going with a larger front accel pump cam but that did not seem to help enough (white to orange).
Any guesses? This issue is so small to the rest of the setup, but I don't mind testing to try and clean up this area too. I basically have my carb setup the way that I feel it needs to be, except for this small issue.

"So when I moved the mains back down to 63's, my 50mph+ cruise is now 14-14.2 again but the cruise to light accel is now mid to high 14's which I can live with.
I am trying to come up with a way to richen this cruise to light throttle back up (like the 64 mains showed) but without richening my 50mph +. The only guess that I have is with larger PVCR's which I think there is only one more step richer than the .071's from QF (.073's). I tried going with a larger front accel pump cam but that did not seem to help enough (white to orange).
Any guesses?"

In my opinion, light accel in the mid- to high-14s isn't going to hurt anything. My suggestion is to check with a vacuum gauge under your light throttle conditions to see how close to the PVC opening point you are. If vacuum is hitting that point, a bigger PCVR may help, but then it will also richen the WOT which will require another round of other optimizations. You're lucky to be worrying about such small nuances!

""My suggestion is to check with a vacuum gauge under your light throttle conditions to see how close to the PVC opening point you are. If vacuum is hitting that point, a bigger PCVR may help, but then it will also richen the WOT which will require another round of other optimizations.""

My vacuum at cruise is in the upper teens, so my thought of the larger PVCR will not work. The cruise to light throttle is minimal and it is time to start worrying about how to slow this car down a little quicker now. Front brake upgrade is next.

I hate to sound stupid here but I have been following along with your post and when you guys use all these acronyms and abbreviations I get lost so could you spell out some of them for me like I know PVR (power valve restriction) but what is PCVR and, where are these things located in the carb. Sorry just trying to learn.
Thanks
Pat Faley

From one lurker to another

These pictures are great references. Studying them can pay dividends!

You may still need to work a bit to figure out some of the acronyms because of minor variation in name or order of words in the acronym. Here is a cheat sheet:

IFR: idle feed restrictions, sometimes called the idle jet. #4 on the second picture, although some metering blocks have them at the top and others at the bottom of the idle down well.
PVCR: power valve channel restriction. #17 on the second picture.
PV/HFPV: power valve/high flow power valve which is a different style PV. I used PVC but that was a typo. #16 on second picture.
MS: mixture screws. #13 in third picture.
IAB: Idle air bleed. This is in the top of the barrels, and controls the amount of air admitted to the idle well which is fed with fuel by the IFR. This circuit controls the fuel/air mix sent to the idle circuit (controlled by the MS) and the transfer circuit.
HSAB: High speed air bleed. This is in the top of the barrels, and controls the amount of air admitted to the main well which is fed with fuel by the main jets and the PV via the PVCR. The HS part is to distinguish it from the idle system, and because it has the most effect at high air flows. The HSAB are closest to the squirter on Holley-like carbs.

QF/QFT is for QuickFuelTechnologies which is a carb vendor.

So what did we ultimately find as the ideal numbers?

I am running my Charger tomorrow for the first time in about a year on a 100 miles round trip. I was gonna jot down the numbers as I went through my stages. It's gonna be fun playing with the numbers because this time around, there are two Carb's instead of one.

I should aim for 14.7 and work my way from there but my current setup is:

~440 Dual Edelbrocks (500cfm each) set up in progressive formation, 10:1 compression.
~727 with GVO, 28" tall tire, 3.55s. At 80mph I am cruising at 2200rpm.
~480/280 Isky megaCam
~Recently installed Edelbrock RPM Heads
~HP manifolds (swapping out to shorty Hedman's in a few weeks
~26" Radiator, 4 core. 7-Blade fan with clutch
~I run 95 octane (Thats the standard here)


I have an Autometer O2 Wideband that I just rigged into a Pelican case and an cigarette lighter plug so it can move from car to car.

I think that the ideal number will be different due to octane, ethynol content, compression, and another factor that I found this year is vacuum advance.
Due to my car running on E10, vacuum advance and 9.7 compression, my current A/F is 13.8 to 14.2 cruise and WOT is 12.5-12.7. Last year w/o vacuum advance, I was able to run 14.8-15.2.

My dizzy is an MSD mechanical. IIRC I have 16º initial with a black bushing (18º) so its 34º total and with the spring combination I am all in at 2600.

There is no ethanol in the fuel here.

Stoich with gasoline is 14.7. Since you have a mild ignition curve and gasoline, you might be fine in the upper 14's to low 15's as a guess.