Too rich, where do I start?

[Mean Gene]

Ok, I am tired of the rich condition of my car. Please tell me where to start to fix the condition. I want step by step from the beginning to track down the fix to this problem. The car seems to perform well, but the smell and black smoke when i stomp on 'er is buggin me. Pipes are black and sooty inside.

Thanx, as always.

[superbee1970440]

How about you post up your combo. It would be helpful.

[dwc43]

Originally Posted by Mean Gene

Ok, I am tired of the rich condition of my car. Please tell me where to start to fix the condition. I want step by step from the beginning to track down the fix to this problem. The car seems to perform well, but the smell and black smoke when i stomp on 'er is buggin me. Pipes are black and sooty inside.

Thanx, as always.

Need to know what kind of carb your running. Most likely you just need a jet or rod change depending on the carb if you have no other problems.

[Mean Gene]

440, 750 Holley w/ vacuum secondaries, Comp. cams split .477/.480 x 268/280, Weiand Action Plus dual plane intake w/ space plate (can't remember size off hand, can measure if needed) stock heads with new springs, lifters, etc. from Comp Cams, MSD Digital Distributor and 6 box, headers, flowmasters, approx. 580 ft. above sea level.

[dwc43]

Check the power valves first. If it's every backfired, they are busted and need replacing. Then take it apart and give us your jet sizes. Most likely if it's only smoking black when you get on it hard only the sec. jets will need to be changed to a lower number. If it's rich at idle you'll have to change the front ones as well.

[451Mopar]

Yep, power valve may be blown.
Also check your vacuum level in drive. If your engine has low vacuum from big cam or low compression you may need to install a lower vacuum level power valve, like a 4.5 or 5.5. From you engine description this shouldn't be a problem unless you have a vacuum leak somewhere?

[superbee1970440]

Originally Posted by dwc43

Check the power valves first. If it's every backfired, they are busted and need replacing. Then take it apart and give us your jet sizes. Most likely if it's only smoking black when you get on it hard only the sec. jets will need to be changed to a lower number. If it's rich at idle you'll have to change the front ones as well.

Primary jets have nothing to do with the idle circut.

When does it smoke? It could be something as simple as float bowl level.

[451Mopar]

right, I have also seen needle/seats that don't seat, and floats that have holes in them.

[cageman]

OH, and I spose the idle circuit has nothing to do with the power side either.

[Mean Gene]

Noticable smoke is only upon hard acceleration. Smell is consistant throughout from idle to full on. I have exhaust turndowns infront of the axle, and there are large black spots on the garage floor from starting the car. Interior (white seats) has black soot as well...not noticable unless you wipe them with a rag. As far as I know, the car has only backfired through the exhaust not the carb.

[Crank]

is this problem ben that way since you had the car or just recently .anyway check flote level if ok then check power valve and see if its the write one .check the diafram on the vacume secondary for leakes or torn ,can you feel the secondaries working the spring could be wrong one,if that don't work then go smaller on the jets .the pump shot and squirters would smoke only on hard exceleration not all the way threw the gears just first gear if their to big.get new plugs and a vacume gage before hand and check them every time you make a change.does the the car bog when you nail it?

[Shaun]

A Holley 750 Vacuum secondary-right? 3310? Where's your idle screws at? I like mine at about 3/4 turns out,from all the way in.
What size jets are you running? 80 is a tad too big for a 750,unless you are running a 260* duration at .050 minimum. 74-78 should be fine for your combo.
You shooters shouldn't affect the rich problem,neither should the secondaries,unless...? Are your secondaries open too much at idle? There is an adjustment on the drivers side of the carb,towards the back-just a small screw that adjusts the secondary butterflies-check it out dude!!!
You may have a bad power valve,but it sounds like a vacuum leak to me. You are getting too much fuel and not enough air. What are you doing for an air filter? And,are you running headers with that 4 BBL? You should be.
Shaun
HP 440 10.8-1 CR TCI Comp 727 3.91 Sure Grip - Low 12's

[Mean Gene]

Problem has been present since I bought the car.
Car has new plugs.
It is a Holley 750 vac. secondary, not sure of the model #,can't find it in the books.
Idle screws are 3/4 out.
Not sure of the jet size, havent taken them out.
Fram large air filter.
Car has headers.

[mhenesian]

Hi Mean Green,

When you have the Holley 3310 apart to change the power valve, check the flatness of the main body where the metering block mates up. You can use any quality machinists straight edge. I bet it's badly warped causing an internal fuel leak. You can "clean" it up somewhat with a medium fine flat file. Also use new metering block (and power valve) gaskets. Jetting for a 750 vac secondary holley should be 72's in front. Standard is the white pump cam and as I recall 0.031" pump shooters. The secondary metering block has been replaced with a metering plate, so there's not much to check there except the snugness of the metering plate screws. Also, check the float clearance with the bowls inverted. The primary bowl should be around 3/16~1/4", the secondary around 1/4~5/16". Since you're having so much trouble, it's probably also a good idea to replace both fuel needles/seats.

I'm not fond of vacuum secondary Holleys, having flogged them for over 35 years (since 1972), and have never ever been satisfied with the performance. (Do I use the yellow spring ? Big bog. How about the brown or black spring ? Where's the power ? Secondaries not opening enough ? Maybe try the orange pump cam and bigger shooters ? Bigger jets ? Lean jets with a 10.5" power valve ? etc., etc..). A 650 double pumper is always better on a street driver mopar. 750 to 850 Holley for race. Today go with Quick Fuel or Proform. Best bang for the buck,

Mark H.

[Jim13]

Sorry it's long, and for an elelbrock, but it's worth it.

Thank Cuda66273 for posting this back in 2001.


"running rich at idle but lean when I am cruising
down the highway"

Yes, lets look at a metering rod and the Edelbrock idle curcuits and
how they work together..bear with me it's late I'm free typing this post
so I may have to repost some other time but I'll try to give an better
understanding of how it all works.

Idle srews: control only the fuel mixture at Idle and have little or
nothing directly related to the cruising or WOT position of your foot.

Metering rods: there is two diameters on the rods and if you look at
them close you'll be able to see the two steps on the rod.
Jets: for simple tuning the jet is just a variable to give you a more
finite adjustment of the metering rods.

Lesson 2.....

"You need Bigger Metering Rods to get more fuel" if someone says this
to you, RUN! as far away and as quickley as possible, never let this
person near your carb with anything other than a polishing cloth for the
air cleaner lid.

"Wire those wieghts open"...just pull out your gun and shoot this
stupid SOB, he's too stupid to own a car.

"Try putting that vacuum hose for the distributor on the bottom
nipple"...send him somwhere to a farm to look at real nipples he has
no Idea what he's talking about...if he picks up a screwdriver get the
sawzall out and cut his hand off.
Lesson 3....

Never let anyone touch your carb, learn how it works and what to
adjust and when, to get the result your looking for...unless... this big,
fat, bald headed guy with a dirty old Dodge hat on walks up and
asks..."Need some help..." don't even answer just hand him the tool
box, listen and watch....and he likes that green Poweraid stuff during
the day...at night it's ET (Early Times) and Pepsi..no Coke, Pepsi
Pepsi....

Ok so here we go, get out your note pads and there will be homework
err ahh trackwork for ya'll this weekend.

You'll need a vacuum gauge, not a good one, I got mine at Baxter's
here in town for $9.95.

Plug the gauge on the lower port on the front of the carb, this should
NOT have your vacuum advance unit hooked to it.....right? Ok
Now lets get the idle down as low as it'll go without stalling, now start
turning one of the idle screws in until it starts to loose vacuum or the
engine starts to sputter, .....now count the
turns as you turn the screw out until the same thing happens. lets say
your number is 2 so now go in 1/2 of that or 1 right....OK now same
with the other side.

Remember to keep bring that idle down to compensate for your tuning, you want it as low as possible so you can get a true reading on the idle mixture.

Now start all over again..Idle, in, out, count and set.

By now you should have a pretty good smooth idle easy huh....

Now lets watch the vacuum gauge 1/2 turn in 1/2 turn out slowly turn
the screw back and forth no more than a 1/2 turn in either direction
until you get the highest reading on your gauge, thats it your
done.....runs good now doesn't it.....set the idle up to your desired
RPM for most of you using a Edelbrock your probably running a pretty
mild engine so 750-950 is probably about right.
Now crack the throttle off idle...sounds pretty good huh :-))

OK now check your timing and set it where you want it.

Start over and do the whole process again...Idle down..the old in and
out...vacuum gauge and now your done.

Secondary circuit...

This is where you need the karma of the Skuza's monkey.

Grab a couple of new spark plugs and a wrench, we're going on a road
test. Find a nice lonely road somewhere, install a new plug in any hole
that's easy. Now stand on that throttle run it all the way through first
and about 1000 RPM below your shift point in second, turn off the key
and release the throttle at the same time. Coast to a stop and remove
the new plug, is the porcelin black brown or white?
Brown is good and probably good to go on the other hand if the plug is
white it's lean and if it's black it's rich. We just tested the WOT
mixture and we now have a baseline on that end of it.

OK put in that other new plug, this time drive the car hard but do not
let the secondary's open, you may want to leave the air cleaner off so
you can hear the carb working and keep it off that deep howl that the
secondary's make when they open. This time run it all the way up to
your max RPM and shut down the same way. Pull the plug and install
one of your old ones and head for the shop.

Remember the two different diameters on the metering rods. The rods
are pulled up out of the jets as you accelerate, the first stage or
primary circuit is the larger diameter of the metering rod, the smaller
diametyer or the tip size is your secondary or WOT circuit.
So let's think about this...the SMALLER the diameter of rod the more
fuel right....remember the rod is lifted out of the jet and because it's
thinner at the end as it's pulled up and out of the jet seat, more fuel
is allowed to flow into the engine....make sense?

For this example we'll use a metering rod numbered 40/60, 40 being
the tip of course.

So let's say for example the #1 plug in our plug test was a little dark
brown almost black and the # 2 test plug is almost white. By our test
we know that #1 plug was wide open throttle so our engine needs less
fuel at WOT so the smaller number of 40 needs to increased to say a
45.

But, the primary throttle circuit is showing a lean condition so it needs
more fuel..so...yup, you guy's are smart, we would drop it to say a 55
so now we need to go looking for a set of metering rods 45/55. and
start all over with a couple of new plugs and back to the road.
This is how I do it and to super tune one of these carbs you really
need a spark plug reader and look way down at the bottom of the
porcelin but for most simple applications this will get you so close
you'll never feel any improvement in the seat of your pants.

I used this method 2 weeks ago on my neighbors 80 El Camino (sorry
but someone has to keep them running or they'd be cluttering up all
the roads)

It's a basic stock 305 last winter we put a Edelbrock RPM manifold, 600
Edelbrock, curved the distributor, headers and he tuned it up to the
best of his ability...it ran 16.40's pretty consistantly but always had a
stumble and was hard starting. I got tired of hearing him crank and
crank the thing and convinced him to let me tune the carb...it didn't
take much convincing....last week the car ran 15.87, 15.91, 15.88 and
broke out in the 1st round with a 15.87 on a 15.88 dial :-((
He checked the milage and it picked up from 14.4 to 18.2! Not
important to me but he liked it.

There's alot more fine points to these carbs but my fingers are tired
and I need to get my ugly sleep. Besides you have lots to work on for
now...

Next lesson we'll discuss:
What those springs that the metering rods sit on do and .....what are
those weights and how do they work?

How about Secondary circuit timing, accelerator pumps and more.....

Goodnight boys and girls....this IS cuda66 for "Mopar Mystery's"
bringing Mo-Power to ya.

See ya'll at Mission Raceways August 8-9-10...I might even take a
pass in that blown 440 Cuda we're bringing.....good thing I got some
"Depends" for my 50th Birthday.....

Oh ya almost forgot...

Depends, Edelbrock and any other products mentioned here are for
comparitive puposes only and their mention is no way to be constude
as an endorsement of their products...unless of course they send me
money which I always need

Eddy Carb Tuning Chapter 2

Edelbrock Carb Tuning Chapter 2:

Well I guess it's time to start getting everyone dialed in on their Eddy carbs, so here we
go. In previous postings I've gone over fuel delivery and basic set up so I'll presume at this
point everything has worked out and the carb your working on is in top condition.

In this chapter of the infamous book we'll look at the baseline of the carb and fine tuning
the transition from idle to WOT.

I continually see Guy's buying a new Eddy and immediately going inside and putting in
bigger jets and smaller rods thinking that this will get them more fuel for their motor, when
in actual fact it gives you more fuel but your not changing the air volume so you just end
up with a rich condition and a "Bog on acceleration"

Let's look at one of the most common complaints that I run into on Eddy carbs.

1. Stumble off Idle

Cause 1: Usually caused by a lean condition for a fraction of a second while the plungers
and springs lift the metering rods and dump the required fuel demanded by the engine.

Cause 2: Not enough initial timing in the motor.

Cause #1 Cure: As the vacuum drops in the manifold it allows the spring under the
metering rod to lift the rod out of the seat and dump fuel. So if you having a little stumble
or hesitation it's usually the spring rate. If you go to the next stronger spring it will allow
the metering rod to open quicker and dump fuel sooner in the transition between Idle and
WOT, of course this is assuming that everything else is in good working order such as
accelerator pumps and timing curve.

By changing jets or richening the metering rods (smaller) you will increase the fuel to air
ratio but not change the timing on the metering rods so you may end up with a stumble
and then a bog until the engine picks up enough RPM to burn all the fuel…sound familiar?

Cause2 Cure:
To fully explain the theory behind this I want to revert back to the basics of camshaft
overlap and the science of the 4-stroke performance engine.

For those engine Guru's out there you can skip this part….

Overlap definition: The position of the valves on the exhaust stroke where both the intake
and exhaust valves are open. This is what creates that lumpy idle and reduces the cylinder
pressure on a race cam at idle and virtually destroys the power band at low RPM.

So what happens?…..When the piston reaches almost TDC on the exhaust stroke and the
spent fuel is being forced out of the combustion chamber the intake starts to open allowing
fresh fuel to rush into the cylinder across the piston and be scavenged by pure velocity out
the exhaust valve basically flushing the combustion chamber clear of exhaust gases.

So now based on the ramp speed of the cam lobe and the exhaust valve slams closed so
the intake can refill the swept volume of the cylinder on the down stroke. Now if everything
is right and the valve size and carb can create enough velocity (or air speed) as the piston
heads toward BDC the fuel charge will continue to fill the cylinder when the piston stops
and hesitates for that split second at BDC basically overfilling it or actually building a slight
amount of pressure in the cylinder. The intake valve slams shut and captures the
pressurized fuel charge. Now we have more cylinder pressure than a static or ambient
measurement of volume and we make more HP. A blower or turbo charger just exaggerates
this phenomena.

So how does this affect the carb tuning?

In an overview we can say that we've increased the amount of fuel in the cylinder through
volumetric efficiency and we've decreased cylinder pressure at idle or as they say, before
the cam comes in, so we need to burn all that fuel we've stuffed in there with relatively low
compression or cylinder pressure.

The only way to do this is to give the flame in the chamber a longer shot at it, so we do
this by increasing the idle timing therefore allowing the combustion chamber a longer
duration in the cycle to burn the fuel, this is why at idle if you start to turn advance into
your motor it will pick up RPM, you not adding any fuel or air your just giving the engine
more time to burn what's available.

In conclusion what we've done by advancing the idle timing is burn all the fuel in the
combustion chamber, eliminated the rich idle condition and removed the stumble off idle.
Depending on how radical the cam and the volumetric efficiency you've created with your
combination, this will determine the amount of advance at idle is required for the best
response off idle for your engine.

Stock: 10-12* or maybe even less
Mid range cam combo maybe around 18-22
Stout runner, try around 25
Full blown racecar…you may have to go up to 30*

Just one more note here…. before you can get your distributor curved correctly you need to
go through this tuning process to determine where to set the idle advance and it's
relationship to the max timing and the RPM you want all this to happen at.

Let's use this quick scenario…. you set your engine up incorrectly and you've got the idle at
1200 to make it run smooth, the idle timing is at 12* and max advance of 38* comes in at
2500 RPM and you send you distributor out to have it curved to this spec.

Then I come along and retune it correctly and advance the timing to 22* and idle it down to
1000 RPM, when I moved the idle timing up it also moved the timing up on the other end
so now at 2500 RPM your max timing is now 48*...look out a melt down is about to occur.
This also reinforces the need for a timing light that you can dial in to determine the MAX
advance, setting a performance motors timing from the idle mark is Russian Roulette.

Well that's it for today, I need to go out and try and pay some bills…

[Jim13]

Here is another one I had saved.

One of the first things to determine is what size carburetor do you need? A number of factors come into play. What cubic inch size is your motor? What do you do with it? Race, street use, towing, street use with occasional trips to the track? What type of intake manifold do you have, split plenum, open plenum, tunnel ram, individual runner? How fast do you spin the motor? What is the volumetric efficiency of the motor? Do you have a manual or auto transmission? What is the rear gear ratio? Do you want to get the best gas mileage possible or do you want to develop the most power possible? Keep in mind that a carburetor is just one part of the engine combination. All of the parts need to work together. Putting a larger carburetor on is NOT going to immediately put 100 more horsepower at your disposal. The carb needs to work with the other parts you have chosen and your intentions concerning how the vehicle is going to be used.
One general rule of thumb uses a formula to determine the CFM requirements of your engine. It goes like this: You need to know the CUBIC INCHES of the motor. You also need the maximum RPMs the motor will be spun to. Finally you also need the VOLUMETRIC EFFICIENCY PERCENTAGE (VE%) of the engine. The first two items (CUBIC INCHES and RPMs), are relatively easy to determine. The engine VE% is another matter. If an engine could use all of the air it ingested, it would have a VE% of 100%. Many performance engines reach this level. Certain race engines can actually exceed this and reach a VE% of over 100% at certain points in their RPM range. Most production engines and most street performance engines have VE levels below 100%. In fact, stock, production, low performance motors will fall around 75%-85% volumetric efficiency.
The math formula is:
CARB CFM =
So if you had a stock, low performance production motor of 350 cubic inches and you wanted to spin it to 5000 rpms max and it had a VE% of 80%, the formula would determine a required carb CFM of 405 CFM. If you had a warmed over street performance motor of the same size, but it was capable of 7000 max rpms and it had better heads, camshaft, headers and a performance intake that raised the VE% to 95%, the formula would give you a minimum required carb CFM size of 673 CFM.
In a controlled situation on an engine dyno, the amount of air actually ingested by the motor can be measured. Since most folks don't regularly have access to a dyno, the above formula will get you in the ballpark. There are some exceptions of course. Using a split plenum type street manifold allows the use of a larger than "normal" carb CFM. This is because the plenum volume is cut in half by the divider, so each cylinder only has half of the total plenum volume and carb CFM to draw thru. Likewise a carburetor with vacuum secondaries will only open the secondaries enough to feed the engine what it needs. Consequently, on a street driven vehicle a split plenum intake with a vacuum secondary carb is the way to go. The vacuum signal stays high for good throttle response at low and mid range rpms. Fuel mileage is good. An "open" plenum intake, generally speaking, has opposite effects. Low rpm throttle response is decreased, but high rpm breathing is improved because of an increase in available manifold plenum volume to each engine cylinder. Consequently, open plenum intakes are a little more sensitive to the CFM size of the carb. If you are drag racing, most folks are willing to sacrifice some low end power for high rpm horsepower. Fuel mileage isn't a concern and the engine spends most of it's time at full throttle. Open plenum race intakes and "double pumper" carbs are the norm.

JET CHANGES AND ALTITUDE AND TEMPERATURE
Holley carbs are calibrated for sea level operation and an inlet air temperature of 70 degrees Fahrenheit. Once you know the correct stock jetting for your particular Holley carb, you can determine whether you live or race at an altitude above sea level. For every 2000 foot increase in altitude, you can reduce the jet size by one size. If you had a carb which has a stock jet size of 80 and you live or race at 2000 feet above sea level, then you would use a #79 Holley jet in the carb. Similarly, a change in the carb's inlet air temperature may require a change in the jet size from the stock calibration. Many racers go a step further by combining all of the weather varibles, temperature, barometric pressure, dewpoint and humidity with the altitude of the track they are racing at to determine the "density altitude". This is a "corrected" altitude above sea level. From there they can determine whether a jet change is necessary to maintain performance or whether to change their "dial in" (if they are bracket drag racers).
You can look at MorTec's HOLLEY CARB INFORMATION page to find the stock, standard, sea level, calibration jets for your particular Holley four barrel carb.

DRAG RACE JET CHANGES and MPH
Drag racers should try to optimize jetting by looking for the jet size that gives the best MPH, rather than best elapsed time (ET).

ACCELERATOR PUMP CAMS AND SHOOTERS
Accelerator pump cams come in various sizes and are color coded and number coded by Holley. The cams have different shaped ramps that the arm from the accelerator pump rides on. By changing the size and shape of the arc on the cam, the pump shot can be tailored to start early or later as you go from off idle to full throttle. Changing the cams can have an effect on the way a vehicle leaves the start line in a drag race. If you leave the line off idle or at a higher RPM (while foot braking or when using a trannie brake or when using a clutch with a manual transmission) experimenting with the pump cams can help. There is no set rule for use, you just have to experiment with the different cams and the different cam positioning holes in the throttle linkage of the carb. Holley sells individual cams or you can buy their kit which includes an assortment of cams to choose from.
Pump shooters are another area of experimentation. Holley carbs come with a standard shooter size which differs by carb list#. If you are experiencing a bog or hesitation off idle, you can try a larger, higher # shooter size. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle postion to the main metering system. The shooters help richen this momentary condition and eliminate the stumble. Keep going up in shooter size until a puff of black smoke comes out the exhaust, then go back one or two sizes. Playing with the shooter sizes is particularly helpful, when you have an intake with a large plenum area, such as a large open plenum or a tunnel ram. Keep in mind that as you increase the shooter size, you may also need a "hollow" screw to hold the shooters in the carb. At shooter sizes over .039, Holley recommends that you use the "hollow" screw (PN-26-12) which allows more fuel to flow to the shooters.

POWER VALVES and ENGINE VACUUM
There is a lot of misunderstanding concerning power valves in Holley carbs. Many 4-barrels come with a particular power valve depending on the carb list# and application. Some carbs have two power valves, while others only have one. The power valves are numbered by the amount of engine vacuum in inches at which they will open and add additional fuel to the power circuit. In other words a 6.5 power valve will open when the vacuum signal on the engine drops below 6.5" and will remain closed above that amount. One of the misconceptions is that they can't be trusted to work because an engine backfire or "belch" can "blow out" the power valve. Many Holley performance carbs models and list#'s now come with built in power valve "blow out" protection which eliminates this problem. If you have an older model carb you can purchase a small, inexpensive, easy to install kit from Holley (PN - 125-500) that will also protect the power valves in case of an engine blowback thru the carb. CENTEK in Redmond, Oregon, (see their website at www.powervalveshield.com ) also sells an inexpensive Holley power valve blow out protector, "Power Valve Shield", which takes about two minutes to install and does not require any drilling.
Many tuners will automatically remove the power valves and use a "plug" thinking this is the "hot" ticket. However, if the power valve is removed and plugged, the main jet size must be increased 6-10 jet sizes to make up the required fuel amount lost by the removal of the power valve. In addition, when the power valve circuit is plugged, the part throttle fuel economy is worsened and may become overly rich. Plug fouling may become a problem at part throttle.
Stock engines can have high vacuum readings (10-18 inches at idle) and the Holley power valves with higher readings like 6.5 to 10.5 will work correctly. Long duration non-stock camshafts and other performance related parts can cause a problem, because engine manifold vacuum may be lowered with these performance parts and the power valve, if incorrect, will always be open, even at part throttle, leading to an overly rich air/fuel mixture. The solution is to choose the correct power valve and to do that you need a vacuum gauge. On a manual transmission vehicle, hook up the vacuum gauge and take the reading with the engine at idle. Then use a power valve that is rated 1-2 inches below that amount. For example, a motor that shows 7" of vacuum at idle should use a 6.5 or 5.5 rated power valve. If you have an automatic transmission, take the vacuum reading at idle in "Drive" (with the emergency brake on and the wheels blocked) and chose the power valve 1-2 inches below that figure. You can get a little more detailed information by driving the car with a vacuum gauge hooked up with a longer hose so you can read it while driving. Drive the car at medium loads and while cruising and note the various vacuum readings. Then chose the appropriate power valve rating.
Holley makes performance style "standard" flow or a "high" flow power valve which has a large opening. "Single stage" power valves are available in 1" increment sizes from 2.5" thru 10.5". There are "two stage" power valves available that are more for "economy" minded users rather than "performance" enthusiasts.

ADJUSTING THE OPENING POINT OF VACUUM SECONDARIES
There are a number of ways to tune the moment when the vacuum secondaries open on a Holley four barrel carb. The vacuum secondaries are controlled by a diaphram and a color coded spring. Holley makes a number of different springs with different tension on the springs. You can change the springs and change the opening moment. The color coded springs run from light tension to heavy:
White - Lightest
Yellow (Short Spring)
Yellow
Purple
Plain (Steel grey)
Brown
Black - Heaviest
If there is a bog or hesitation when the secondaries open, the spring tension is too light, go to the next heavier spring. Holley offers a kit (PN-20-13) which contains one each of the above color springs. When you change springs you'll note that the stock cover over the spring and diaphram is not all that easy to get to. Holley makes a special cover (PN-20-59) that makes spring changes quick. Finally, Holley also makes a completely adjustable thumbscrew operated diaphram cover (PN-20-99). This cover limits the travel of the diaphram and therefore limits how far the secondary throttle plate can open. It makes secondary throttle opening adjustable. It's very nice to have if you are a bracket racer and are using a carb with vacuum secondaries. You can adjust the throttle for changes in weather and track conditions or for changes in your "dial in".

I know it's overkill for your question, but I thought it a good opportunity to repost a some great info.

[Mean Gene]

UPDATE..............

Still working it out guys. Thanx for the info JIM13, most helpful.

[dave571]

A couple of basics.....

Float level will have a drastic affect on mixture, regardless of carb type. Check it out through the whole.

Idle mixture screw setting will affect it too, but more so at idle, than through the range

Jet size is the most normal way to adjust it on a Holley. If properly done, the rears will be 8 sizes bigger than the fronts. This is due to the power valve flowing the equivalent of 8 jet sizes on the front, at Full load.

Check what size they are. I would think a normal street 440 would have 74-78's in the primary's depending on a lot of variables.

[Mean Gene]

Well, the front float bowl was high. Fixed that, but the gasket leaked when i screwed the bowl adjuster shut. So, after a long wait, i received a gasket kit for the carb (it is a 3301 by the way) from my local shop. Anyway, I had adjusted the idle mixture screws last night I was re-checking the timing, and while checking the advance at 2500 rpm, I noticed cylinders 3 and 5 had the header pipe cherry red! Can anyone explain this?

[Mean Gene]

I just pulled the plugs...3 looks perfect, 5 is white. Whats goin on here?

[451Mopar]

If you have a dual plane intake, it may be one side of the carb is not getting much fuel. Since it is a holley carb, it may be there is something in the jet or air blead. I would pull the fuel bowl and metering plate and blow out all the passages with carb cleaner, then make sure the jets are the same size.

[Mean Gene]

It is a dual plane, but I would think it would effect more than one plug? The car also has an inconsistant idle and a dead miss from idle to slight throttle. A kind of "chug...chug" like one cylinder is dead.

[Mean Gene]

More updates...the car has a consistant 12 psi on the vaccum gauge and in timing, anymore than 30 degrees advance at 2500, I get pinging.

[dave571]

Check for vacuum leaks.

BUT I suspect you have a more serious problem, valve etc.....

A compression test may be in order.

[Mean Gene]

yikes!!!!!!!!!

[Mean Gene]

Did a compression test and all cylinders are between 150 and 160. I am thinking the headers are just cheap thin walled and thats why they are getting red. My water temperature gauge stays between 160 and 180 degrees, but I noticed spark arcing from the plug boot on #3 and the boot had melted...this is WITH the spaceage boot covers on them!! they are just too damn close to the headers. I replaced that wire, took it for a spin, then realized another boot on the right side had melted too!!! This is crazy. these are brand new wires...total now 3 ruined!! So, my next step is to heat wrap the headers. What do you think?

[Shaun]

Originally Posted by Mean Gene

Did a compression test and all cylinders are between 150 and 160. I am thinking the headers are just cheap thin walled and thats why they are getting red. My water temperature gauge stays between 160 and 180 degrees, but I noticed spark arcing from the plug boot on #3 and the boot had melted...this is WITH the spaceage boot covers on them!! they are just too damn close to the headers. I replaced that wire, took it for a spin, then realized another boot on the right side had melted too!!! This is crazy. these are brand new wires...total now 3 ruined!! So, my next step is to heat wrap the headers. What do you think?

Headers getting red means you are getting too much unburned fuel in your exhaust. Do you have a split pattern cam?I can't remember if you posted your cam specs,or not. If you do,this may be your problem-if your exhaust flows more than 70-80% of your intake,when you have a pretty good overlap.
However,your headers getting red-due to unburned fuel-may be because your plugs weren't firing(most likely),because of your plug wires being burnt.
I like HI-ENERGY Wires and I also run header wrap on my 440.
Wrap does two things for you; it keeps the engine bay cooler and it keeps the exhaust gases hotter(which makes them move faster-hotter air being more dense is lighter),so it improves performance and keeps your plug wires from burning so easy.
I haven't tried 'em,but Accel has header plugs that are shorter and it helps keep the wires away from the headers and makes it easier to get your plugs in and out with the headers on.
Shaun

[Mean Gene]

Comp. cams split .477/.480 x 268/280

[Shaun]

Did you get her figerred out? Try retarding the ignition timing to 28-30 overall advance and disconnect your vacuum advance,just to see.
One more thing,try taking the carb off,just after running it and see if the mani is wet with fuel. Your carb could be leaking where you can't see.
And do you have adjustable rockers? Make sure they aren't too tight. They could be keeping some valves partially open.
Also,do you have a good strong spark from your plugs? Your coil may be weak,or you may have your spark plug gap wrong for the voltage your coil is putting out.
Shaun

[Mean Gene]

Timing is at 30 total currently. No adjustable rockers. car has an MSD ignition system including Billet distributor. Plenty of spark.