Set up:
225cid, 9.5: 1 compression, over size valves, ported, big cam, Clifford intake & shorty headers with duels to bumper, 904, 3.55:1 Suregrip


About a year ago I installed an o2 sensor to aid in dialing in the old Holley which has been a challenge since getting this car in 08. Using the sensor to dictate jet selection has been helpful. For several thousand miles a pair of 54 main jets have been installed causing a slightly rich condition at all speeds, slightly less rich condition under light acceleration where power valve is not activated, and a wildly swinging lean to rich condition under WOT which I have been lead to believe is normal at stoichiometric mixture.

Several days ago I dropped down one jet size to 53, and at first did not see any difference putting around town, and rural highways at sub fifty mph. Today I had a chance to drive in different environments from in town, country roads, to interstate where a constant higher rpm could be maintained.

In town air fuel gage sits at slightly rich as it did with 54 jets, slight no power valve acceleration gage dips in to normal, once back to steady speed settles in at slightly rich. Out on interstate with tachometer rover 2800 the slightly rich reading slides into normal and light acceleration it dips into lean, and as speed increases slightly back to rich normal. At this rpm, 3000 or so, under WOT mixture returns to the rich side of normal.

Dose this leaning of mixture at 2800 to 3000 rpm indicate the secondaries are cracking open? An event I have never been able to determine at what rpm this takes place, and when running up hill with a heavy foot I suspect that they are opening because the engine starts to pull strongly. I do know if I drive at 65 mph, fuel economy drops off, at first I attributed this to the brick aerodynamics, but now wonder if this is where the secondaries are coming in during steady cruse. A sub note once rpm gets to 4600 rpm I do know vacuum increases two inches to 18 under constant throttle, so cam profile is entering into this performance algorithm as well. Perhaps the cam’s excessive overlap is contributing to low rpm rich condition as well.

Lastly since installing 53 jets, after engine has been off for fifteen minutes, I get a rich reading for several minutes. I don’t know if this is because electric choke is closing a bit or something is going on with idle circuit, or if this is a hot fuel bowl condition causing a temporary high bowl level.

So I guess what I hunting around for are some of your Holley 390 antidotes while I ponder dropping jet size an additional notch to 52, and try to figure out why it runs a little rich at low speeds, leans out at higher rpm.

Last fuel mileage check yielded 18.5 mpg at speeds of 3000 rpm (60mph) or less, and no lead footing…

Bill

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

At what RPM is your main circuit starting to flow (fuel from boosters)? Around town you should still be on the transition circuit.

Remember, decreasing a jet size on a Holley reduces the amount of fuel in the main well, which in turn leans out both the main and transition/idle circuits. At low RPM putting around town you are still in the transition circuit, as well as low rpm cruise situations.

What is your AFR at idle, 1000, 1500, and 2000 rpm? If the idle/transition circuit is too rich it will combine with fuel from the boosters to create an overly rich condition.
What is your float level set at?

With the engine running at the highest rpm before main circuit startup slightly adjust the idle mixture screws and watch for rpm changes. If it speeds up when you tweak the screws your transition circuit needs some tweaking (IFR). If it drops off with a turn in either direction you are just right.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

First off, gage is this [url=http://www.bing.com/shopping/style-line-air-fuel-ratio-gauge/p/583B02455A6174525011?q=air+fuel+ratio+gauge&lpq=air%20fuel%20ratio%20gauge&FORM=HURE] SunPro [/url]. A you can see lean and rich has three positions, and ideal four.

[quote]What is your AFR at idle, 1000, 1500, and 2000 rpm? If the idle/transition circuit is too rich it will combine with fuel from the boosters to create an overly rich condition.[/quote]

While running down road constant throttle at 1500, to 2500 rpm middle predominantly, and first light flickers occasional from ideal.

[quote]At what RPM is your main circuit starting to flow (fuel from boosters)? Around town you should still be on the transition circuit.[/quote]


This engine idles in park at 1000 to 1100 rpm, and lopes at 800 in gear idle. I have set the throttle plate so there is only 0.020â€￾ of transition slot in primary showing at idle. Secondary idle circuit is set to make up enough air so that idle mixture screws turned out about 2.5 turns. I think power valve 4.5; my notes are not clear. Enrichment is activated when vacuum drops below 4.5â€￾, not by rpm.

At idle in gear mixture goes lean, off the gage. I’m not clear if this is because heated sensor is located too far down stream at header collector and crappy combustion due to big cam overlap, or in fact mixture is lean. Once rpm come up to 1000, mixture jumps to middle rich light. When engine is idling in gear vacuum gage shows 6 to 8 inches on a good day. In park idle I get 9 to 10 inches of mercury as engine comes out of lope.

When idling in park, gage will dip to lean occasionally than quickly swing back to mid rich; when dipping to lean, a slight stumble can be detected. I suspect this has something to do with cam overlap, and a temporary poor vacuum signal.

I do know that often idle drops below 800 in gear at which point enrichment circuit activates. This happens when slowing to a stop at a light. When this happens a shift into N, and a throttle blip returns a better air fuel mixture, or just waiting it out without throttle impute the vacuum recovers enough to stop enrichment.

Occasionally when aggressively slowing from highway speeds to turn onto another street, engine will stall once idle rpm gets to 800 or less. In the past I have been able to tune this nasty stalling habit out, and engine will just lope along without stalling long enough to get back on the throttle.

Last time I checked fuel level in bowls, it was at bottom of sight hole.

Later this morning I shall retune idle mixture, and fiddle with idle rpm.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

But at what RPM is fuel starting to flow from the boosters? With the car in park look down the carburetor and slowly increase the idle speed via the idle speed screw. Take note of what RPM fuel starts to flow from the boosters.

As for the idle mixture, with the car in gear and the parking brake set and the wheels FIRMLY chocked, adjust the idle mixture until you get the highest possible reading on your vacuum gauge. Then take it for a drive and see if it does better.

Ideal mixture screw setting on a Holley is 1 1/2 turns out. Sounds like your idle mixture is a little on the lean side. What's your current IFR and IAB size?

Also, I suggest a wideband o2 gauge. I have an AEM UEGO in my truck, and it made dialing in my 2300 a lot easier. I wound up going with a quickfuel metering block so I change the size of my IFR's and PVCR's.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Main jets, or power valve? Holley has no boosters. There is idle circuit, transition as it progresses to run from main jets once throttle plates have opened enough, than enrichment from vacuum activated power valve when needed for acceleration.

Ideal mixture screw setting on a Holley is 1 1/2 turns out. Sounds like your idle mixture is a little on the lean side. What's your current IFR and IAB size?

I may have too much air entering past secondary throttle plates. As you know one has to remove carburetor to adjust this stop. Just another Holley PIA. I have been screwing around with idle mixture, and current setting is 2 ¾ turns out. I’m beginning to think there is just too much slop in throttle shafts contributing to poor vacuum quality at idle. Also I belive this big overlap cam has some contribution to poor idle adjustment.

Also adding to this mess; mechanical timing is now advancing too soon around 1200 rpm, not 1500 as it was when I recurved the distributor three years ago. Because of this, idle sometimes won’t settle back down to correct rpm which upsets the in gear idle rpm setting. I have a 2600 stall converter.
Translate the alphabet soup please.

Once the engine cools off a little I’ll pull the carb, and address the secondary throttle plate stop adjustment. The last time I made this adjustment a few months ago it was with Holley tech support.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Change-out that big cam and tuning will be a lot easier.
DD

Yes a Holley has boosters, it's those little things sticking out in the middle of your venturi with the bar across the top.

PM me your address, I've got a book I'm going to send you.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

[quote]Yes a Holley has boosters, it's those little things sticking out in the middle of your venturi with[/quote]

Got it, I just call that housing a venturi and or a discharge nozzle. So in other words you want to know at what rpm the main jet begins to carry the load.

I took it up to 3000 rpm, no fuel emitted from booster. Perhaps it needs a wider throttle opening with engine under load. At 3000 rpm I’m pulling about 15 inches of vacuum with steady throttle.

What is the title of the book, I may already have it.

This afternoon I screwed around with the carburetor settings. Removed the cab, reset the secondary throttle plate adjustment stop by closing them up a little more so now there is no transition slot showing, but not closed fully. This adjustment allowed turning idle mixture screws 3/4th turn. Now they are just shy of two full turns out, the least amount of turns since owning this chunk of iron… Also now have 10 to 11 inches of vacuum at 1100 rpm in park idle, also a better reading than all others.

Ingear idle is another story, the engine won’t sit in gear and idle without tickling the throttle. Problem is the power valve is activating as rpm drops below 800 which in turn causes still lower rpm. I may have to drop back down to a 3.5 PV. The drop off is not immediate, so it is not an instant stall condition, and easy to deal with by sliding into natural, something I have had to do all along.

The problem with 3.5 power valve one has to onto it hard before enrichment kicks in. the 4.5 or 5.5 that is currently installed made for quicker throttle response out on the road without flooring it.


Reading in Urich’s book, he states “as jetting gets closer to ideal, vacuum will increaseâ€￾; I’m beginning to see this trend.

Doc:
[quote]Change-out that big cam and tuning will be a lot easier.
DD[/quote]

I know, I know…. Easy for you to say, I don’t have an engine puller handy, or a way to install new cam barrings here at the “Needmore Garageâ€￾

If I do get a way to pull the engine, I may as well pull the pistons for a ring inspection. I suspect #5 may have developed a problem recently, that could be causing some of the lope effect.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Where’s the fun in that Rick? LOL

Just to refresh my memory, I think new carburetors have been discussed previously several years ago, but I don’t recall which carb was recommended; help out the old guy’s atrophied brain here. I’m thinking Edelbrock performer… 400 -500 cfm perhaps… At any rate it was a carb that utilizes rods, not jets and stinking power valves.

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Yep, the Edelbrock 500 / 600 are much more user friendly and usually run well out of the box. (Not that they don't need tuning) But they seem much more forgiving than the Holley.

Just one man's opinion.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I 2nd the Edelbrock 500. They are very easy to tune and hold a tune.

_________________
82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Bill,

I agree, get and Edelbrock 500 especially with a wild cam. They are not as persnickety as the Holley 390 and work amazingly well. You can quit scratching your head and pulling out your hair and just have fun driving......even with a wicked cam. Adjusting the springs, jets and rods are very easy to do and no leaking fuel every where while you do it......
I would save your pennies and get a 500 with the electric choke.

My wife loves the Edelbrock carbs over the Holley especially on her car. She didn't like me always working on the Holley....Edelbrock's are easy to set up and then forget it. The AVS is even better....

I would change the carb first......then get one of Docs RV295 RDP cams. It's quicker.....you will always be fiddling with the Holley 390.

By the way, re-lube your distributor to keep those weights moving.....oil the wick too under the rotor....

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I do that every year or about every 3-4000 miles. I had the distributor all apart a month ago to clean and lube the governor mechanism as I thought it was sticking; it wasn’t. I may try the other black light duty spring that came with the distributor curving spring kit to see if it keeps the weights pulled in better.

I keep hearing good things about the Edelbrock carburetor, and maybe it's time to set this tired twenty year old Holley aside.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

This evening I swapped out a 4.5 power valve to a 3.5 PV, still using 53 jets. Idling in park 1050 rpm, and running steady throttle down the road, A/F gage illuminates middle rich light, under slight acceleration lights of ideal illuminate, harder acceleration before power valve opens, she dips to lean, and swings back to rich so all lights in between illuminate at the same time. I take this to indicate that the mixture is real close to what it should be. Once PV opens, gage reads first light to mid rich. Where I have stepped down to 3.5 PV to improve in gear idle at low vacuum levels, the cussed and inconsistent dreaded engine spin-back when ignition is killed seems to have left the room…

Nothing more embarrassing than pulling in somewhere, folks gawking at the car, and the engine has an epileptic fit spinning backward ending with a pfffft death rattle… This does not happen every time, sometime just half turn of the crank is all she can muster, or occasionally a perfect shutdown with no spin.

I must be getting closer. I’m going to give it one more shot with a 52 jet in a few weeks after seeing how well the 53 jets behave.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC