I broke down and bought an Innovate Motorsports LC-1 wideband kit to help me tune in the Duster. It never really seemed right as it would bog a bit when you opened the throttle and I get terrible gas mileage (if i'm breaking 10, i'd be shocked).

Anyway, I have the wideband connected to the passenger side exhaust pipe right behind the header collector (I have TTI headers now). I've got the gauge mounted on the a-pillar.

The car is running a 360 with magnum heads, summit 218/228 .441/.441 cam, tti headers, 600 holley, and the low compression stock shortblock...hooked to a 4-speed with 3.23's.

We unfortunately run E10 fuel here...so 14.1:1 or so is ideal (14.7:1 on E0-all gasoline)

Anyway, the car behaves as follows:

Tip into the gas, the air fuel ratio leans out to about 16-17:1 for a second or two then settles back into the 13-14:1 range on light accel

at steady state low rpm cruise it sits in the 14-16:1 range, but as soon as the throttle is lifted off it richens to 11.4:1-12.8:1

at idle its between 12.9:1 and 14.4:1 depending on the throttle conditions before idling.

at WOT after a second or two it sits at 12.5:1 which seems pretty much ideal.

This is your standard Holley 600cfm 4-barrel carburetor with electric choke...(80457). I already jetted it up two sizes from 64-66.

I'm mostly trying to help the driveablity of the car. I'm really beginning to wonder if this carburetor is not properly suited for this application. I've thought about changing it...but I'm not sure to what...have been looking at Edelbrock AVS carbs as they seem to be the most fine tuneable aftermarket carb out there due to the step metering rods, air door, etc

Any advice would be appreciated!

Make sure the acc pump arm is adjusted properly and once you get that, then you may need a larger nozzle shooter.

The lean off idle is most likely pump shot or power valve related. Most Holleys that I encounter have a 6.5 power valve. Changing to a 9.5 usually helps more than anything else for me. I get my pvs from AutoZone or O'Reillys because they don't charge shipping.

It's a shame the Innovate forum is shut down. A lot of good info was there...

I'm also using Innovate WBO2 (LM1 + Auxbox with rpm, vac, accel). It sounds like you're using the car on the street, so that's the way I'm going to comment.

The off idle tip-in is most likely acclerator pump. I just went through this this weekend. I was getting a lean spike as you add throttle from idle to about 1800 rpm. It also felt very dead in that range. I switched from the red pump cam to the white and problem is almost entirely gone. But if you see a spike up followed by a spike down (rich) then you might want to change the shooter (discharge nozzle).

The rich 'cruise' is most likely because the throttle blade is back down to the transition slot. This is is not easy to adjust on a Holley. If this is the case, the solution is to reduce the idle feed restriction or open the idle air bleeds.

Before going that route, see what is happening at idle (in gear if automatic). Where is the throttle blade in relation to the transition slot? Only about .020" of slot should show beneath the blade. How far open are the idle mix screws? Also make sure the fuel level is about right.

But yes its possible that the carb is set up for a more aggressive cam. If your engine produces better manifold vacuum at idle than the carb was intended for, then its going to be rich.

Have you used logworks chart function? Its good for steady state analysis (not acceleration) if you have rpm and vacuum and/or throttle position data. I'll try to attach a jpg of an example.

Good. The attachment worked. I agree the Eddy's are more easily tunable than the 4150/60 series Holleys. No drilling and tapping, blah, blah, blah. But you may be giving up too early. You've probably heard it before, but don't tune to an AFR or Lambda number. Use the data as reference points as you seek most power and economy.

Tune the main jets for max power on the dragstrip (best mph) or a dyno. If you use a dyno, you may have to richen a little on the drag strip. Note the temperature and humidity (and altitude).

Sometime the jets for the best power are also the best (leanest) for highway use. However, you can experiment going leaner if you want to get into resizing the power valve channel restriction.

Accelerator pump shot we've already mentioned in the previous post. Setting the initial throttle position so the transition slot opening below the blade looks like a square (yes you have to remove the carb) helps obtain good control with the idle mix screws. The idle mix screws should be set for best manifold vac when the engine is warm, or about 1/4 turn richer from when its too lean. Idle and transition circuits come into play every time the throttle blade is nearly closed, not just at idle.

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Nearly closed results in the highest vacuum readings for a given rpm. As a result, on the chart of afr for vacuum and rpm, the diagonal represents throttle position. In turn, throttle position mostly determines the circuits doing most of the work. In the example chart posted, the power valve did not get activated.
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IMHO the best explanations on how Holley carbs work is in the book by Urich & Fisher and published by HP Books. Good illustrations and some pretty good tuning advice. Even after reading Vizzards 'How to build Horsepower' books, various magazine and web articles, some of which are really sophisticated, I still find the HP book is still a great reference.

I can't datalog anything but A/F ratio vs time...as I only have the LC-1...no aux box or anything like that. I have a manual vacuum gauge I plan on hooking up so I can take it for a drive with it installed. Unfortunately, its raining today so that's not happening today.

The car idles with 14 in Hg vacuum at idle in neutral (its 4-speed). the cruise is fairly lean at a low throttle opening but richens when the throttle is closed...acts fairly strangely.

I started reading about it a bit...is there an effect on the mixture depending on the air cleaner I am using? I have the 1972 340 trap door one on the car at the moment.

Not tuning to A/F seems different especially since that is one of the major feedback loops in a fuel injected vehicle...other than throttle position, MAP, and sometimes MAF.

""The car idles with 14 in Hg vacuum at idle in neutral (its 4-speed).""

I agree with above post. I would have guessed higher on the idle vacuum, maybe in the 15"-16" range. How much initial timing are you using at what idle rpm?

You've gotten some great info so far. I'd just like to expand on one thing Mattax touched on - the condition where you get rich as the throttle opening is decreased - presumably while decelerating.

Mattax mentioned that you should have no more than .020" or so of transition slot exposed at curb idle. Atached is a photo that illustrates the point. The exposed t-slot should look like a square - no more. Is this something you've checked yet?

During deceleration, the manifold vacuum is much higher than at idle. Any exposed t-slot allows additional fuel to be sucked in through exposed t-slots. Remember to check the secondaries too, as some people crank open the secondaries to get the primary blade/slot relationship right. Exposed t-slot is wasted fuel. If necessary, there are other ways to get bypass air so you can get the blade/slot set correctly.

The easiest way to minimize this problem is to get the idle vacuum as high as possible, or more correctly, to reduce the difference in manifold vacuum between deceleration and idle. Remember, orfices that sized perfectly for 14" hg are too big at 22" hg. The greater the difference between idle and deceleration vacuum, the worse this problem becomes.

This is just for future reference (you've got more basics to cover before you even consider this) but in some cases, it it necessary to install transition slot restrictors to improve on the problem you're describing.

Again, you've gotten nothing but good advice above, IMO. I just wanted to expand on the solution to one of the many challenges you face when you attempt to get your carb calibration right side up.

Jim

I have no doubt that the transfer slots may be exposed more than 0.020"...the car does not seem to idle at a speed that is fast enough for it to stay running when coasting down to a stop light without having that cranked open more than I'd like although I will still have to remove the carb and find out. This is the primaries. The secondary curb stop does not seem to be adjustable on this 2003 vintage 80457 carb (its an 1850 600cfm with electric choke). I'm idling the car at 800-850rpm.

I'm running 14 degrees initial and 35 total for timing on this car. The engine has 8:1 Federal Mougal pistons and magnum heads so the compression ratio is still low...likely 8.4-8.6:1. The car seems to like 16-18 degrees of initial timing, but the denso mini starter has a hard time with a hot restart at these levels.

That being said, I may need to add a fuel pressure regulator. I have a holley fuel pump that is putting out about 7 1/2 psi. I noticed that fuel dribbles out of the boosters when you shut the engine off.

For the most part the car runs really good. I'll have to work on it a bit and get back to you guys. The weather hasn't been cooperating the last few days.

"I have a holley fuel pump that is putting out about 7 1/2 psi."

Definately add the regulator then see how it reacts to the pressure change.

One more thing...I don't see where you've told us where the idle mixture screws produce the best idle (how many turns out from lightly seated). That's also important when trying to figure out what's up.

Shout back when the weather gets better.

Jim

I agree. So to recap
1. Get the fuel level correct by adjusting the floats and changing pumps or installing a regulator. 7.5 psi is pushing the limit for Holley 4150 needles and floats to keep under control.
2. Check the primary and secondary idle throttle positions, and after correcting (1) reset the mix screws.
3. Make sure there is no slop between the accel pump cam and the lever arm at idle. No preload either .

When you are checking the transfer slot, write down the relationship between turning the idle speed screw and the throttle-transfer slot opening. That way, you'll know how much is exposed without removing the carb each time you adjust it.

Just took it for a quick in town ride and ran cruise vacuums at a variety of engine speeds. It never went below 13 in Hg on cruise and spent most of its time at at least 17. when backed off the gas its about 25.

Apparently the air cleaner changes things because its idling with 17" hg vacuum with the air cleaner on.

Its very difficult to get down to the power valve opening of 6.5" hg. almost never happens unless you open the throttle a good bit (more than half i'd say). Any standard type acceleration happens in the range above its opening. Going to get a 9.5 PV and probably jet it back to 64 from 66 for the next time out.

I will also order a regulator...sounds like I need one. Will check the transfer slot opening when i am messing with the fuel lines.

Good discovery!

Can I talk you out of making a jet change and a power valve change at once? I'd advise you to change just one thing at a time. I know it sounds like a pain, but it's really the right way to go about it.

Jim's right.
Maybe I wasn't clear when I posted that little 'recap'. What I meant was that each of the points made were valid, but also that they should be done in sequence.
First, the fuel level has to be correct and stable. A regulator will help get you there, as could possibly a different pump. But you have to adjust the fuel level or the results from any other change is questionable at best. If the needle and seat isn't too large, you may be able to get it it pretty good even at 7.5 psi. But yes, a regulator or lower psi pump will insure there is no creep in fuel level.
Second, get the idle readjusted. Idle settings effect more than just idle.
Third, make sure the acclerator pump is actuating immediately on throttle movement. Then once it is, change pump cam and shooters if needed.

These are the basics that need to be addressed first. The sequence will make more sense once you start reading that book. You can read the first 20 pages or so on-line via google books.

Well guys...I did the following:

Pulled off the carb and confirmed the throttle blade position...pretty much a square...no trouble.

I added a regulator and set it for 5.5 psi. The car immediately began to idle cleaner and it no longer drips fuel out of the boosters on shutoff.

I did swap in a 9.5 PV and some #65 jets. Other than a low speed surge on cruise (i richened the idle slightly), the A/F ratios are really good. It even idles at 14:1 now. With the new PV, as soon as I go to take off from a light, i'm in the PV and there isn't any hesitation.

Its close enough that I'll have to look at it in a lot of different scenarios. Its good enough that I should get OK mileage and the driveablity is better.