If you have access to a drag strip, I think that jetting to the best MPH is easier for most of us to set the WOT mix.

Just make enough back to back runs to establish a solid MPH base for comparison. Then jet up until the MPH starts to drop off, then step back to the optimum.

If at that point you want to start consulting the plugs, then okay.

It is much quicker to change main jets than to pull a spark plug on a hot BBM. And you do not have to learn the intricacies of reading the spark plugs, unless you want to.

I am not saying that this will result in a perfect A/F ratio. But it will get a good reliable result with a reasonable amount of effort and knowledge.

Greg,
Here's what I've leaned -

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I recently had the heads ported and changed to thicker head gaskets to lower the compression. Previously it was near 11.0 to one with 190+ cranking compression and detonated on the pump premium 91 octane gas we have here in CA.

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It would help if you knew the current compression. With CR we can make a pretty good guess if the engine will be octane limited and less timing will be a neccessary work around. Do know the cc after the heads were cut?

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I have an AEM wideband EUGO air/fuel guage in the car with an O2 sensor in the RH header collector. Currently with the Grant 850 Demon carburetor I am able to get it to idle in the mid 14 ratio in neutral and in gear. Part throttle and full throttle are under 13.0 and even richer.

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Assuming high overlap cam (compared to stock), a little richer at idle will be better. Better becaue it will make more power and therefore little to no drop in rpm when shifted from N to D on an automatic. Target idle AFR 12.7-13.5 Take a little initial timing out to match the richer mixture. This is a good reference for estimating initial timing based on cid, and cam duration.
http://www.demoncarbs.com/Tech/DemonSelectionGuide.asp

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I've stumbled along in life tuning cars by how they feel rather than using any type of guage. Most of my experience has been with stock or mildly modified engines. This car raises the stakes and I want to get it right.

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Feel still has a place. Use it in conjunction with your WBO2 AFR for low speed, light throttle and cruising. If it feels weak or delay at low speed, you now will know what the AFR is, and see which tweak makes a change that helps. Same at highway. If you're driving at 60 mph and get lean surge, drop it to 55 and you'll see roughly how lean was too lean. Then install bigger main jets and see exactly if that helps 60 mph but also what impact it had on 55 mph.

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Is it fair to say that since I am able to get the A/F into range at idle, I should be able to get the part throttle and WOT into range with jets and power valves?

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Yes. Although some BG and more recent Holley carbs need modifications to do this well. Try what have, as it is, first.

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Even though it reads that it is too rich, I smell no fuel and see no black smoke. I recall reading that for WOT the goal is in the 13.0 range but what is a good goal for part throttle?

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WOT is a maximum load situation, especially in upper gears. Anywhere from 12.5-13.2 AFR depending on engine and fuel. With a little Eth mixed in, slightly richer will not surprise anyone. If more combustion cooling is needed, a little richer may be needed. Target range 12 - 13 in your case.
Part throttle depends on load and with a racy cam, rpm. At low rpm, richer mix is needed because of the exhaust diluting the air-fuel mix. Same issue as at idle as mentioned above. As rpm picks up, this problem goea away. Also load increases, lean mixtures can be used. How lean depends on your motor and loads. Drive it at 60 - 70 mph and see what it likes and how lean it will go at light throttle. At light throttle, when it gets too lean it will just try to die and then recover (surging). Don't wail on it! If there is too much timing, and you put load on it, bad things can happen and being lean isn't going to make it better.

At some point, as load increases, the mixture needs to get richer, much richer. This is when the power valve needs to kick in. When possible I like to dial in the WOT before the cruise. Safer in my opinion. Take it to the drag strip or a dyno and get best mph or hp under the curve. You can adjust this with the jets. Later, if there is a difference between the jets for best power and the jets for best cruising at 60 mph, you can look at the fuel curve and/or the power valve restrictions.

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Last week when I drove the car I felt a bit of an off idle stumble and lower idle vacuum. I thought I read here that it is suggested to set the timing to the highest manifold vacuum. Am I remembering that right? Currently it is set to 19 degrees initial and 33 total without vacuum

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Uh. Alot of us thought that, but its not quite right. In neutral, there's no load, so you can keep adding timing and the engine loves it. You can then lean it to match and the engine loves that too. Then you put it gear and it goes. Ugh, the load is killing me.
Try setting the timing around 16 or 17, whatever the chart recommends. Then, using your vacuum gage, adjust the fine idle fuel mix for best vacuum. On an automatic, in theory set fuel mix for best vacuum in gear. In real word, it's often easier to set in neutral, then richen it about 1/8 turn and check it in gear.

Illustrations and explanations:
IMO the best book to start with is Urich & Fisher's Holley Carburators and Manifolds published by HP books. No BS. Urich was VP of Engineering at Holley, and the diagrams and explanations are top notch for a basic understanding of how any fixed venturi carb works. Many finer points are touched on or illustrated as well even though not discussed in detail. I come back to this book and notice things I didn't pick up on before.
You can find a g**gle book version, or go buy the real thing, used or new. Older editions just as good.

There's a great explanation and diagram in a sidebar on throttle relation to transfer slot. If you continue to have issues with off-idle, this is the section to look at. The throttle blade relationship to the slot is very important for idle and off idle AFR. Your Demon may have 'idle-eze' which means that if you can't get the proper throttle-slot relationship, it is not neccessary to drill the throttle plate. Instead you slightly open the idle-eze.

Todays report:

* Idle in Neutral 1100-1200 rpms 13.1 to 13.5
* Idle in Gear 750-800 rpms 17.8 to 18.0 +

* Slow acceleration from 2000-3500 rpms 10,9 to 11.6
* Slow acceleration from 3000-5000 rpms 11.9 to 12.4

* Steady cruise @ 40 mph in OD 12.9 to 13.3
* Steady cruise @ 50 mph in OD 12.0 to 12.5
* Steady cruise @ 60 mph in OD 11.9 to 12.3

* Faster acceleration from 2000-3500 rpms 11.5 to 12.0
* Faster acceleration from 3000-5000 rpms 12.6 to 13.1

* WOT in 2nd gear, 2000-3500 rpms 12.9 to 13.1
* WOT in 2nd gear, 3500-6000 rpms 11.8 to 12.5
* Repeat run 11.6 to 12.1

*********************************************************************

With this info, I see that I need to richen it up a bunch at idle in gear. It stumbled and stalled twice while leaving 2 different stop signs. I suppose that since this occurs at idle and not on the primary circuit, this is a matter of tweaking the idle mixture screws?
I wouldn't think it would need more accelerator pump volume would it?

The "Slow acceleration" between 2000-3500 and 3000 to 5000 showed it to be really rich. This was done at light throttle , I assume entirely on the primary circuit? This makes me think I need to use smaller primary jets.

Steady cruise at 40, 50 and 60 were done in overdrive resulting in a final drive of 3.05 to one. The numbers there are more like what I'm supposed to have at WOT.

The faster acceleration testing showed leaner numbers than the slow acceleration. This was still done without hearing the secondaries open. I'm not sure what to make of that. Maybe I need a power valve that opens sooner there? I have a 3.5 in the carb now.

At WOT it shows that the higher RPMs it goes fatter. I guess that is safer than leaning out.

I welcome any suggestions or comments on my findings.
My gut tells me to adjust the idle mixture screws to obtain a richer in gear reading. It tells me to lean out the jetting front and rear. I'm not sure what to do regarding the Power valve. I'm not sure if I should use a lower rated one than the 3.5 I have.
Please tell me what you think!

Try inserting a skinny wire in the idle air bleeds in gear to see if that helps on the idle AFR If it does that means it wants smaller idle air bleeds which enrichen the mixture from idle to WOT On the fat when cruising you might be able to lean down the transition fuel feed channel, take the carb. apart and look at the slot in the middle of the throttle body that the throttle plates straddle, I drill and tap them for a allen head #6 brass set screw and then drill the set screw to make the channel smaller, make sure and figure out what size the stock hole is before drilling and tapping I bought two numbered drill bit sets, 1-60 and 61 to 70 with a pin vise to work on carb. circuit slike those You can make the babys (carbs.) purr like a satified kitty As already said work on one circuit at a time, remember the idle circuit, the transition circuits, the primary and secandary as well as the power enrichment circuots all work at WOT The idle and high speed bleeds should be used for the final fine tuning BTW, check your ignition timing from idle in nuetral to idleing in gear to see if that rascal is dropping the lead out of the mechanical advance at the lower RPMs Keep at it, you know your having fun and learning, correct

Uhhh...^^^^^^ Cab, your post has my head spinning!
I just knew that there was MUCH more to tuning that just a few jets and a Power Valve.

NICE TUNING REPORT!

* Idle in Neutral 1100-1200 rpms 13.1 to 13.5
- You need to be careful with this high of an idle. You may or may not be on the idle circuit and may lead to your metering screws no longer giving you the adjustment that you need. Your Neutral idle readings should be second in importance since you have an auto tranny. After tuning your carb in D (see below), the Neutral A/F readings may just be what they turn out to be.

* Idle in Gear 750-800 rpms 17.8 to 18.0 +
- I always suggest to tune an auto car in D with the emergency brake applied or someone holding the brake. I would suggest that the next time you have the engine warmed up after a short drive, put the car in D and apply the E brake. Then readjust your idle mixture screws for the best vacuum in D at the rpm of your choosing. You may need to keep readjusting your rpms as you go around the carb readjusting your metering screws.
-How many turns out are each of your metering screws?

I would work on the above first before moving forward to the cruising changes. These changes may affect the next tuning process.

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* Slow acceleration from 2000-3500 rpms 10,9 to 11.6
- This could be a rich "transition" into the mains or it could be rich "main" jetting. If you could tell us what size Idle Feed Restricters you have, we might be able to give you a guess. Or, If you wish to lower your main jetting 2-4 sizes and retest your 2000-3500rpm A/F readings again, this might tell us too. If the large change in main jetting does little/nothing in the A/F readings in this rpm range, then this might point to the IFR's being to large which would be causing the rich readings. If the leaner main jetting changes the A/F readings by a point or more, then you know that your main jetting is where you are getting your fuel in the 2000-3500rpm range. A little testing in this cruising area will give you allot of info for your tuning in the near future!!!

* Slow acceleration from 3000-5000 rpms 11.9 to 12.4
- See above. Start with the lower rpm tuning first because the 3000rpm+ numbers may change due to the above idle/transition tuning changes.

* Steady cruise @ 40 mph in OD 12.9 to 13.3
* Steady cruise @ 50 mph in OD 12.0 to 12.5
* Steady cruise @ 60 mph in OD 11.9 to 12.3
- See above
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* Faster acceleration from 2000-3500 rpms 11.5 to 12.0
* Faster acceleration from 3000-5000 rpms 12.6 to 13.1
- See above
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Test WOT last.

Note: As already mentioned by another member, the idle/transition/main circuits TRANSITION into each other. There is no switch that turns one on and the other one off. When you change the idle circuit (IFR's, Metering Screws/Idle Air Bleeds), these changes will also affect the "transitioning" (you might be cruising on the transition circuit at lower rpms: "IFR's & Idle Air Bleeds will help tune this area) affect into the main circuit. This is why you start at the idle circuit with your changes and then move your tuning efforts up the rpm range. (All of these changes at the lower rpms will affect your higher cruising rpms and your WOT results). This is why you test WOT after all of the other circuits are tuned ON A STREET CAR.

Your notes that you have taken are invaluable in your efforts of tuning. Keep these notes to show yourself how far you have come in the weeks to come.

Note: Your main jets may or may not affect your cruising A/F numbers under 3000rpms or so. It just depends on the carb. Some carbs use the transition circuit for cruising and some use the main circuit for cruising.

Greg. Which circuit is doing what and why will make a lot more sense if you get that book. Used copy will be $10 including shipping through 'zon. It's also avaliable online through g**gle books, at least sample sections for free.

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With this info, I see that I need to richen it up a bunch at idle in gear. It stumbled and stalled twice while leaving 2 different stop signs. I suppose that since this occurs at idle and not on the primary circuit, this is a matter of tweaking the idle mixture screws?

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Yes and maybe. Yes it is a matter of adjusting the idle mix. Maybe it can be done with the mixture screws alone, but that is where you should start. See paragraph above where I wrote what the engine would do if too lean at idle. " Then you put it gear and it goes. Ugh, the load is killing me."

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I wouldn't think it would need more accelerator pump volume would it?

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Get the idle and transition half decent before playing with pump shot.

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The "Slow acceleration" between 2000-3500 and 3000 to 5000 showed it to be really rich. This was done at light throttle , I assume entirely on the primary circuit? This makes me think I need to use smaller primary jets.

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No. Definately not on the primaries in the lower rpms, maybe or maybe not the high rpms for reasons that Y0 already explained.
In my experience, primary circuit starts to dominates the fuel delivery somewhere around 60-65mph (about 3000 rpm) with factory tire size and street gearing. That is, about 25-6" tire diameter and 3.23:1 gearing. This will vary with booster type, venturi size, and air bleeds along with engine load and gearing all factor in.

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The faster acceleration testing showed leaner numbers than the slow acceleration. This was still done without hearing the secondaries open. I'm not sure what to make of that.

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This is exactly how it should be. I was not clear in my explanation above. Once the vehicle is moving, as the throttle opens with increased load, the AFR should get leaner.

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Maybe I need a power valve that opens sooner there? I have a 3.5 in the carb now.

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Not just based on some AFR number, and certainly not based on what you observed. See previous comment. Power valve needs to open when the load gets very high. This can be anywhere from 60-90% full load. Once you get the rest figured out, you can experiment opening the power valve under less loads. It shoud not kick in hard, nor should it make the 3/4 thottle acceleration lazy. Not easy to nail down without lots of trials or very sophisticated equipment which few of us have.

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At WOT it shows that the higher RPMs it goes fatter. I guess that is safer than leaning out.

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Yes and could be one or more reasons for this. Also 2nd gear isnt always the same as 3rd gear. Another reason to reserve that for later.

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My gut tells me to adjust the idle mixture screws to obtain a richer in gear reading.

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Yes.

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It tells me to lean out the jetting front and rear.

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No. One change at time. Even making just one change at a time within the idle circuit is very hard to do. Urich and Fisher will show you why far better than I, and they have diagrams.
My guess is that besides the mixture screws, you will have to try a little more and little less timing, and you will also end up adjusting the throttle position with the idle speed screw. IF that's what you end up doing, here's a time saver.
Take the carb off and measure the transistion slot visible under the throttles. Use a feeler gage or some wire of known diameter. About 0.020" - .035" should show. Write down how much slot shows for every quarter turn of the idle speed screw starting from the screw just touching to .040" Put the carb back on with the idle speed screw opening the throttle so just around .020-.025" of the slot shows.
As you tune the idle, once the engine is warm, you should be able to get it to idle nice without opening up the throttles more the .035" or shutting them more than .020" You see even at idle, the transition slot is contributing both fuel and air. Every time the throttle's idle position is moved, that contribution is effected.
So, first set the throttle so so it runs, but no more than .040". Then adjust timing and mix screws so it doesn't die when put in D. Then adjust for best vacuum in D. You'll have to experiment with a degree or two each way on the timing. As it runs better the rpm will go up, and you may have to adjust again. It's that type pf process. If you can't get the results needed without opening the throttle around over .035", then its time to let some air in through a hole. Your carb may have the 'idle-eze'. Instructions for that feature should be available from Grant, if that feature is on the carb. Urich and Fishe explain this under 'wild cams' and why getting this right is important for the off-idle performance.

No vacuum leaks. I sprayed carb cleaner around all points of potential entry, then repeated it with Ether. No leaks were found.
I just adjusted the idle mixture screws to 2 full turns out. The idle vacuum didn't change much but now it runs much better idling in gear. The prior setting was just shy of 1 turn out from the seats. Not sure why I had them set so far in. I think that I was trying to achieve the best vacuum # while idling in neutral. This time I aimed for a richer reading in gear. Before it would idle rougher and sometimes stall when accelerating. Now the rpm drop when going into gear is only 200-250 rpms. The A/F readings in gear went from the high 17s to under 13.0. It feels much more responsive off idle with the richer mixture. This carb has idle mixture screws in both metering blocks. I was surprised to see tha A/F readings changed by turning the screws in the rear metering blocks. I wouldn't have expected that. I thought the idle circuit was only related to the primary side.
Hopefully I'll have more time to tune over the weekend.

The Holley and other Holley type carbs. that have four corner idle circuits idle on all four corners Continue on , kind sir, your making progress

Nice job!
Try to keep all four metering screws outward about the same amount during your tuning. Then once you have it dialed in and you just need to compensate for outside temp change, you could then just turn the front metering screws for minor adjustments. You will have to keep tweaking the A/F when the temps change through out the year, but it will now be a quick adjustment.
You not only richened your in D idle A/F, you have also richened your off idle and low speed A/F too.

Weekends are my time to spend on the car, so tomorrow I'll get back to it. I'm going to map the readings from just the mixture screw adjustments. I agree that it looks like I'll be running even richer than before and need to swap in smaller jets.

You needed to richen your idle since it was in the 17 range. You fixed that problem and now it is time to work your way up the rpm range.
After you make the next test run and if you see a rich condition off idle and lower cruise rpms, you will next need to check the IFR sizes and let us know.
Nice job!

Yesterday I changed the Primary jets from the # 86s to #84s. I figured that since it was running so fat at all points, I'd lean it out and see what numbers I'd get.

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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.

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Every number at every point showed improvement:
Idle neutral:...... 13.6 to 14.6 Up from 13.1 to 13.5
Idle in gear:...... 13.6 to 14.3 Down from 17.5 +
Slow acceleration 2000-3000....... 11.6 to 12.0 UP from 10.9 to 11.6
Slow acceleration 3000-4500....... 13.1 to 13.6 UP from 11.9 to 12.4
Steady cruise @ 40 mph...... 13.3 to 13.6 UP from 12.9 to 13.3
Steady cruise @ 50 mph...... 12.7 to 13.1 UP from 12.0 to 12.5
Steady cruise @ 60 mph...... 13.5 to 14.0 UP from 11.9 to 12.3
Faster accel 2000-3000...... 12.8 to 13.3 UP from 11.5 to 12.0
Faster accel 3000-4500...... 12.9 to 13.1 UP from 12.6 to 13.1
WOT in 2nd gear 2000-3000...... 11.9 to 12.5 Down from 12.9 to 13.1 ?
WOT in 2nd gear 3000-4500...... 11.6 to 12.1 Even from last test.

The only changes were the jets and adjustment of the the idle mixture screws.
The 850 came with # 85 primary jets and #92 secondaries. Right now I have 84/94. Power feels good. Zero detonation but it obviously needs to lean out a bit more. Car feels more responsive when driven below the 3000 stall of the converter but still not as tight as I'd like. Someone mentioned that running rich may make it sluggish at low speeds. The tests of slow accel & faster accel from 2000-3000 rpms are a bit dicey since the slippage of the converter doesn't really load the engine like it does over 3000 rpms.
I haven't pulled the plugs for a look-see yet. I don't have an "in-car" vacuum guage to know what I'm making at any rpm points under a load. ZERO smoke is visible and I smell no over-rich mixture.
At this point I wonder if I should try one size smaller primary jets to see if I can get these numbers closer to the goal. I suppose that what I am after is a balance of what results in the most power without going too lean? I obviously have no dyno for testing HP, only the tradional Seat of the pants dyno.

Lean the front down only one jet size and take it for a drive BTW, what spark plug do you have in it now, heat range or number and brand? Lots of fun maxing a tune up on a motor huh The perfect results are worth it

I have the spark plug part # somewhere. They are the NGK equivalent of the Champion RC9YC gapped at .035.
I know it seems silly, but I am curious as to what mpg I might get! last year I got 12.8 on a tankful coming back from Van Nuys. That was with the 509 cam, a point more compression but running too rich.

Nice Job!
Creep up on it one jet at a time since this change is affecting most of your cruising readings.

Idle in D: Low 14's (If you have your strongest vacuum reading, then this is good)
Light Accel: 11.6-13.6 (Rich 2000-3000rpms= Leaner main jet)
40-60mph Cruise: 13.1-14.0 (Try leaning it out a little more to find your lean limit = Leaner main jet)

Leaning out the main jet will lean out your light accel and every reading the rest of the way up the rpm range. Your carb appears to be setup to cruise using the main circuit. Some do and some cruise on the transition into the main circuit. Now that you know, it will make your cruising tuning easier.

Once you know what your strongest vacuum reading is in D, then as the outside temps changes, then tweak the front two metering screws to keep you in that range through out the year.

Thanks for the feedback. I appreciate any and all help that comes my way.

I'm curious as to what effect adding Vacuum Advance might have on the A/F readings. I meant to work on the car after work but didn't get the time.