[Half-Inch Stud]

Interesting Chart (seensomething of the sort many years ago). Shows main jet diving to zero % on the right, and main air bleed staying at 100% during maximim air flow. Figured those to be reversed.

See, i would like to thoroughly understand that chart. Can't even make sense of it. Help help help.

[Tom Vaught]

Don't think you are reading the chart correctly and making assumptions that are not necessarily true.

I will give you a magazine article to read that shows some Air Bleed testing at Westech Dyno.
Normally do not pay to much attention to their runs but in this case the info matches pretty close to reality. There is a "tightrope" that you walk on with air bleed corrections. The engine will tell you if it is happy but again, the dyno is not the track and a number on the track might be better but the engine is leaner under those track conditions. More power but more chance to hurt stuff.

So here it is, take it for what it is worth, you might understand it a bit better as it is a pretty simplistic article vs a typical carb design graph.

http://www.hotrod.com/articles/mopp-...m-carburetors/

You are also dealing with a Proform carb and not a true Holley carb so who knows what is inside of it and the calibration.

So what was the point of the picture you attached?

Tom V.

[Half-Inch Stud]

Originally Posted by Tom Vaught

Don't think you are reading the chart correctly.......
So what was the point of the picture you attached? Tom V.

Showing that my 1050 came with a choke, & date coded 1970. Probably good metering block design and passages?

[Tom Vaught]

PM me if you want advice for your specific 1050 carb, this sticky is not meant for personal advice like in the race section.
Tom V.

[Tom Vaught]

Just so you don't think I was putting HIS off on his very rare 1050 Dominator Carb, IF I posted info on modifying a similar part number Dominator carb from a later production year, he would have destroyed the value of a very unique Dominator Carb offered to the Public in the 1st year of production. Not Racer Only units.

Later I will talk a bit about ASSUMING things that you read.
I will say that a 4150 style carb is not a Dominator Carb and adjustments for the .020" window in the Transfer Slot to Carb Blade Position WILL Be WRONG if messing with a Dominator Carb.
More like .005" window or a covered window from the top looking down but a filed edge exposing a very small slot.
This has to do with the size of the Dominator Carb in relation to the Idle Air Flow the engine actually wants.
A Dominator carb can be made to idle at 850 rpm and be happy with a big duration camshaft (in a Pontiac Engine)
using proper carb techniques. That being said, the camshaft type and spring pressures must be considered for the idle rpm too.
More later.

Tom V.

[Tom Vaught]

PM back to you HIS.
Tom V.

[Half-Inch Stud]

Idling at 900 RPM wth 9.0:1. My Problem is the Local track is 1/8 th mile and that is so demotivating to arrive-ready to evaluate anything when i'm used to 1/4 mile. Seems the diffs are at the top-end for Holley vs Q-JET.... vs manifold types...vs dual quads.

--> Tunng. Dialing-in off-track. Wondering if you know a useful street-based tuning proceedure for dialing-in a Holley (1050 or any DP), on the back-Streets, so a fella knows that it is up-to-snuff on the1/4 mile track with slicks?

[Tom Vaught]

You read my mind, here it is HIS:

Tonight I will give you a bit of advice concerning modifications to Holley Carburetors (or their clones).

1) There are aftermarket Metering Blocks out there from Quick Fuel /Holley that allow you to swap BACK to the factory calibration just by removing the Metering Block that did not work with your mods and by putting the factory Metering Block back on the carb.

2) A second advantage, when I work on people's carbs in the eastern part of Michigan, is:

a) We go for a "drive around the block", over on Lake Shore Drive, see some nice homes, look at the water (Lake St Clair), and I get a chance to identify the Carb issue myself on the person's vehicle.

b) Rather than just tear into the guy's carb and start messing with stuff, I typically know what model number it is and have a set of "MASTER" Metering Blocks that we can quickly install on that series of carburetor and take it for a second drive around the block.
If it drives good then we know he actually has a Carb issue and we work to make his carb Metering Blocks "look" like my Metering Blocks.

c) If those do not fix the issue then we look for a engine related issue: Vacuum leaks, adjustments wrong, Ignition issues, etc.
EVERYONE WANTS TO BLAME THE CARB AS THE 1ST STEP IN THE PROCESS. I learned from Dell Forest (the WW-II Instructor and Chief Mechanic) not to assume anything. KNOW what is wrong or find out what is actually wrong before blaming the carb.

d) So if the alternate Metering Blocks did not fix the issue(s), and we did not find any obvious hoses off the engine, cracks in the hoses, vacuum leaks, etc then we move on to the Carb Main Body.

At that point we take the carb apart and look for obvious things wrong or mods maid by someone else. But by swapping the Metering Blocks we got a chance to quickly look at the fuel bowl float settings, the inside of the bowls, the Needle & Seat function, and the Accelerator Pump Shot when we installed my Metering Blocks on the person's carb.

Plugged Air Bleeds, partially plugged air bleeds, (had a fly's leg in one of the air bleeds one time at work). Drilled out Air Bleeds (I use pin gages and Holley information to check that for mods by others.
If it is driving poorly at non Power Valve Modes then looking at a Power Valve is just making busy work for the customerc on his dime.
That being said, I do use a remote (hand held) vacuum gage and typically always let the customer do the driving. That is why Holley always had two Engineers in the vehicle for a drive evaluation. Then they would swap positions and drive the route again.

So I leave you with those bits of info to think about tonight.

If you get into a quick street car like Charlie66's Turbo 4 cylinder 64 Tempest (at 30+ psi of boost), Charlie has other things to do so a rider is a good idea. We had lots of Engineers at work who should never be in a 600+ HP street car. Few knew how to get the Manual 6 speed Trans in the right gear under full power and over-revved the boosted engine.

Tom V.

[STEELCITYFIREBIRD]

"not to assume anything. KNOW what is wrong or find out what is actually wrong before blaming"

This what separates the best from the rest!

[Tom Vaught]

How a Wideband Air/Fuel Meter can be tricked (unfortunately) to read the wrong AFR on a Dyno
This post is all about why the Air/Fuel Meter used in Racing is not PERFECT and can be TRICKED (wrong readings) if you put a engine on the dyno in the wrong mode by using a given fuel, by running the engine for a period of time on the dyno and when the engine parts get broken in with each other.

The article was written by a VERY SMART Dyno Guy/ Good Carb Guy named Shrinker (from Australia) on the Carb Forum I used to post on before it shut down. Shrinker passed away early in life RIP.
A Ford Co-worker (but REAL PONTIAC GUY) named Chris Piper is a DYNO EXPERT with many years of experience and many thousands of hours running and analysing Dyno Data for Ford Research. He would understand all of this post. Maybe you can too. Not my strong point Dyno Testing and Data Analysis.
The point is Shrinker gives a very good example of how the Engine's actual Air/Fuel number on the dyno and the Air/Fuel reported on the meter can be wrong. So I am posting his info for you Dyno Guys to digest.

First is Part 1, word for word (from Shrinker) about what happened on the Dyno Testing

Then I will post Part 2 with the Shrinker analysis of why the Dyno Air/Fuel Meter was reading wrong during the testing.

Finally I will summarize what I personally learned from the Shrinker articles about Carbs and Dyno Testing (and I have seen thousands of tests).

So here is Part 1 of the Shrinker Articles

I had an experience the other day I thought I'd pass on. I and my engine builder were on the engine dyno with a SBC 400 tunnel rammed race car engine. It has a pair of quickfuel 750's on it I had setup for it. We started the first day by running the engine in on avgas, well it was supposed to be run in by the time the dyno guy said it was, but i never believe that. So anyway we started some pulls and used Sonoco 112 race gas.

The dyno is equipped with a meter box type Lambda gauge, I dont know the exact brand etc, it doesnt matter, it reads the same as my innovate stuff when Ive hooked that up there before so i just used his being on leaded fuel etc. I took my picoscope (a laptop data logging oscilloscope) to the job just to watch the combustion from that point of view.

It was interesting only analyzing the tuning from the point of ignition traces alone. I tell you everything you need to know is shown on a scope. If your not getting the first part of the process right, like the firing KV and the duration and flame kernel development your not going to make for it on the rest of the stroke.

Anyway the first few pulls were showing up really rich at lambda .83. Dyno guy was grizzling at me its too rich, so I pulled the plugs out and they were white, well I'm not going to lean this sucker off am I. I told the dyno guy its not that lambda; that's an incorrect reading, the engine is making too much CO (I could see it on the plug) from inefficient burn and its inferring your reading, there's noting wrong with the carby setup.

Ive told you guys on forum many times about plugs reads that are white with grey tinge when the AFR is supposedly rich and how that possible to happen. So I say "nah not leaning it off yet, go change the timing". So we give it 2 degrees more and its still reads .82 and the plugs are still white and the power went up a tiny bit. So I look at the scope and think for a bit and say this fuel is not right for this engine as it stands now, we send the owner off to go get more Av-gas.

The scope was showing the crane Hi-6 was only achieving 2/3rd the duration time of spec, the systems working great but there is way too much ringing left over in the coil so there is plenty of energy but its wasted. The firing KV's were 12kv and that ridiculous for a supposed .83 lambda or even the lambda I knew it was.

Anyway we get more av-gas and give it a pull and it makes 10hp more than the sonoco 112, the dyno guys still rabbiting on about his lambda gauge and saying its too rich. Still reading 0.83. Pull some plugs out and its getting some tan now so we keep fiddling.

I blocked the bottom e-bleed because that was part of my plan, I deliberately left the bottom bleed in in-case it went above a power level I wanted to make sure it went rich. So no problems put a blank in the hole and swapped the e-bleed into the IFR so it leaned out the bottom end. That all worked good made it run better down low but it still read 0.83 lambda on a pull.

Notice how he has made a lot of changes on the Dyno and the Lamda reading on the air/fuel meter has not changed.

The firing KV's were down to around 8kv now with the av-gas, so that was getting better but it was erratic not consistent firing KV. I was a little bothered by the scope readings, its telling me the engine is insufficiently compressing the mixture, but we charged on.

Did some timing runs and plug gap tests etc and got the power up another 10hp, but then it started to ever so slightly pepper the plugs. Then we did a compression check on the motor and low and behold the compression had come up 25psi, So much for saying the engine was run in before huh.

I could tell the engine was now making too much HP per cube for av-gas, so we swapped back to the sonoco 112 and low and behold it now loved it, the plugs reads were good, and the scope was full duration arc with consistent 7kv firing on the fuel. Everything was now falling into line.
And guess what the lambda was reading 0.87
The dyno guy shut up because It was fixed by NEVER changing a main jet, just like I told him at the start.

Tom Vaught

[Tom Vaught]

More on this topic a little later today
Tom V.

[Tom Vaught]

Ok, Lunch is over so back to the second part of the Topic (DYNO TESTING vs Air/Fuel Readings)

Article starts here:
So what really happened with this engine? We never changed a main jet and yet the AFR went from lambda 0.83 to 0.87 (12.2 to 12.8 on a standard gas scale) Thats a 4% change in fueling with actually changing the fueling. When I changed the IFR size it didnt change the lambda reading so it wasn't that change that did it. So what did change?

People are taught by every Wideband manufacturer in the world that they are accurate tools for reading the AFR. And yet here is an example of not actually doing anything that actually has bearing on the AFR, AND YET IT CHANGED.

ANSWER:
What happened was the engine became "RUN IN". (Broken In") And the timing was adjusted for best power.

So why does that result in a different reading?

Its all to do with the species of gasses output from the chamber. You have to look at the percentage of each species to understand why. As a burn progresses the chemicals produced go through stages until the final outcome is for a perfect burn just water and CO2. Our engines don't get to that stage but they get to the stage of producing water and CO and CO2 and a little bit of NOx and having some O2 left over. The point to consider is that it takes time to go through the stages to get to the final result.

The most important stage is the preparation prior to ignition. When that is not right, as in this engine, the flame kernel doesn't grow fast enough and the result is a lower cylinder pressure at an equivalent crank position to a good kernel. The flame kernel is a growth of laminar conditions to around 20mm diameter, then the conditions change to turbulent flame and the speed of burn is much faster. What you have to know is its droplet size and the vaporization that influences the speed of both laminar and turbulent flames. So when an engine has large droplets its needs a lot of heat to vaporize them in the time available.

(AND HERE IS WHERE A PROPER CARBURETOR CALIBRATION COMES INTO PLAY -TV)

When I say to you guys that a particular engine hasn't got enough vaporization that is what I'm commenting on. How it looks inside the cylinder is like this, the AFR at ignition time is leaner than the average of the cylinder, lets say the average is 12.8 but at ignition time the AFR around the plug is AFR 14, the flame is going to grow slow and some of the flames energy is going to used in vaporizing the fuel thats not gas yet. So the flame kernel doesn't generate enough heat and you dont get a TAN plug, you also run the risk of extinguishing the flame if turbulence is poorly directed.

(AND HERE IS WHERE A GOOD HEAD DESIGN COMES INTO PLAY -TV)

The kernel uses up about 10% of the mixture then the conditions transition to turbulent. Once the flame is turbulent it cant be extinguished. However the conditions toward the remainder of the chamber ahead of the flame kernel front are still under vaporized, therefor requiring energy from the advancing flame front to vporize mixture ahead of the front, not an efficient way to go. It's the burn angle duration between 10 and 90% that matters. Good burns are in the range of 15 to 25 degrees. Burns of engine with poor vaporization can be as long as 45 degrees. THAT'S WHY some engines make best power at timings like 38 to 45 degrees compared to another engine that has best power at 28 degrees.

The burn time determines the peak cylinder pressure. Its the peak pressure that is one of the principle determining factors for the production of CO into CO2. If its not high enough you wont get the conversion underway so the exhaust contains high values of CO. If the CO is produced with a high oxygen consumption then the exhaust stream will be low in O2.

Now a WB theorist will tell you that the WB will use the unused O2 to convert the CO into CO2 etc and complete the burn to perfection and report a result. Well that's correct but the reality of this type of burn is that the O2 is used to make excess CO and forgo the conversion to CO2 because it just didn't get hot enough for long enough. This type of burn is far from correct as the theory books only want to consider.

There isn't the normal correct balance of O2 to CO of a rich burn. The CO2 levels are low and the WB catalyst needs the CO2 to break it apart and get some O2 to reform the CO to CO2, the reaction of which is O2 neutral. So the WB has to get the O2 from the outside air and that causes it to report a high O2 requirement thus richer than truth.

I fail to understand why the industry doesn't educate people to correct this anomaly. The only manufacturer who is game to come close but they dont realize the reason why is Innovate, their system goes into error 8. But they fail to list this cause in their error reasoning help chart.

SO THE REALITY OF THE DISCUSSION (TV)

Article starts:

I've found that Widebands report erroneous readings when the gas in the exhaust is high in CO and also high in O2. That is an unnatural situation. HC levels are not a problem to a WB, its the CO that is the trouble maker. The problem is without a gas bench you have no way of knowing if the reading is correct or not. A gas stream of high CO and high O2 is a dangerous one, it means the engine is not making its power potential and it means there are going to be excessively lean areas in the chamber. So when you look at the plugs and they are not a dark enough tan for the AFR your running you can pretty well assume the engine isnt preparing the fuel enough prior to ignition.

This is the reason why we use Gas Analysers at the same time we use Air/Fuel Meters and Exhaust Temp Sensors when testing on the Dyno.

So whatever you do don't tune off the WB, tune off the plug. The engine of this thread is not a bad one, its pretty good actually because I've seen WB's up to 1 or even slightly over ratios out of truth.

You can't put nitrous on an engine with that sort of issues, well people do but they rely on the fuel to get them through.
I've run engines in perfect combustion scenarios with correct gas balances and even with perfect combustion as in zero CO and O2 and HC and only CO2 and I've seen how plugs look.
I have experience at ranging the AFR around the plug from the plug color. I can tell you this issue is the most common thing I see.

So that finishes his post. Some really good info there. So purely counting on a Air/Fuel meter without having knowledge of how to read a plug might get you into a lot of issues with the engine and the Holley Carb Calibration

Tom V.

[Tom Vaught]

So in simple Tom Vaught terms:

Learn how to read Plugs and don't trust the Air/Fuel Meter to be the Final Word on the Air/Fuel mixture going on inside the engine.

Tom V.

[Half-Inch Stud]

Yez interesting. Were you also able to read the plug THREADs for plug heat level from thread color?

[Tom Vaught]

Some can read them better than I can, but I am ok on the electrode and a bit down on the insulator. Shrinker was a PRO, (I was told) on that deal.
But again I am just posting suggestions to this thread (Not making assumptions based on just one piece of information from one piece of equipment.)

Tom V.

[Tom Vaught]

Tune-up for a 9381 (830 cfm) 4150 Carb As every engine is different these are just common mods for that carburetor)

1) Remove the Rear Power Valve, Jet that side up 8 jet numbers (you can always drop them down a number or 2 later) and add the Jet Extensions I have mentioned in the past along with the Whistle Mods.

2) If the carb already has "Screw In" Air Bleeds you are good to go, otherwise you need to remove the pressed in bleeds and tap the holes for either screw in Holley bleeds or short stainless (drillable) set screws.

3) The Idle Feed Restrictions (which I talked about in the past) need to be in the "lower position".
Drill out the upper IFR restrictions to .100" for free flow to the lower IFRs.

4) Many times you can go from the .037" - .038" IFR to a smaller IFR sometimes as low as a .032 IFR.
If you need more you can always slightly increase the size. Making a hole smaller is TOUGH, LOL.

5) You can also increase the stock Idle Air Bleed to .070" and leave the Primary High Speed Air Bleed in the .026" or .027" stock diameter.

6) You can leave the Power Valve Channel Restrictions at .067" but if your carb has .059" Restrictions you can open them up to the .067" number

7) Primary Jet should be 73 (if you have it or 74). Secondary Jets should be 85 or 86 Jets.

8) Stock Squirters should be .031" and you can leave those alone.
Blue Cam on the front and stock rear accelerator pump cam on the rear.

9) Primary Jet should be 73 if you have it or 74. Secondary Jets should be 85 or 86 Jets.

10) You want a smooth idle in gear about 13 - 13-2 to 1 Air/Fuel Ratio.

11) Cruise Air/Fuel Ratio in the 14.5 to 14.7 Air/Fuel Ratio area.

12) WOT in the 12.6 to 12.9 Air/Fuel Ratio area.

Depending on what Pump Cam is on the Secondary might require further tuning (later opening preferred).

This carb should be happy on a small 240 degree roller cam with 10.5 compression ratio. A bit less CR will probably still be ok depending on the quench distance (piston to head). People are starting to pay attention to that more (finally).

You want the normal 18-20 degrees in the distributor with about 16 degrees initial. But see what it likes.

Real simple calibration which should run fine once you move the Idle Feed Restrictions, open the upper restrictions to .100" and mess with the Idle Air Bleeds. On Cliff's 4781-2 old 850 carb he had to go up slightly on the Idle Air Bleeds but later when the carb was on the engine on the dyno they said don't ever touch this carb, it is perfect.

On the old carbs sometimes minimal changes are ever needed to be spot-on.

Tom V.

I am not going to provide a Generic Dominator Calibration as there are a bunch of them out there and Jeff (Shaker455) does a fine job on Dominator Carbs.

[Tom Vaught]

One other comment on the Rear Power Valve.
You can buy the Rear Metering Block Power Valve Plug (and think that you are good to go) but the reality is you will also have "cross-talk" between the two Metering Block Main Wells at high jet flows.
So if the Metering Block has a provision for a Power Valve the common remedy to also add Power Valve Channel Restrictions.

On a boosted carb you can tune extra fuel flow with these restrictions and on a NA Carb you can also, if you want, put in blank plugs (thereby removing the main well "cross-talk" and then add the Power Valve Plug. It is the little mods that many people miss in the Carb Magazine Articles that can make a difference.

Tom V.

(You want the Main Jet for one Booster to get the true signal from that Booster, not the average of two Boosters at high fuel flows.)

[Tom Vaught]

Tooski had a question about a Secondary Metering Block that did not have a kill bleed hole in the emulsion channel. Some metering blocks were built with only one emulsion bleed and no kill bleed. Holley Metering Blocks have had several locations where they drilled the kill bleed hole. Most times it intersects with the main jet feed passage to the booster inlet.

In this case I told him that farther up the emulsion channel (near the top of the block) are 3 depression dimpled spots. I told him to drill a hole in the second dimple from the top using a #71 drill bit as that is a common hole size for metering blocks with kill bleed hole in that area.

So PMs work well and then after we work out a solution at times I may post up the fix if it seems like it would be beneficial for everyone.
Like I said there were metering blocks without any kill bleed holes but for his deal adding one will not be an issue to the calibration or the emulsion circuit.

Tom V.

[Tom Vaught]

Today I am going to post a couple of pictures of a 3 circuit Dominator Metering Block.

Years ago Holley had 2 Circuit Metering Block Dominators and they ran fine. Then some people decided that if two Circuits are good, then three Circuits have to be better, Right? Marketing People. And they were right, Holley sold a crap load of Three Circuit Holley Carbs. And in many cases the three Circuit carbs gave the slow guys bragging rights at the Dairy Queen with their Dual Dominators on their Supercharged "Sticking out of the Hood" Chebbys. And they never had issues with the carbs because they never really exceeded the Air/Fuel demand of the Carbs.

But now you take the Real Race Guy.
At some point he is going to make big power with his Single Dominator Carb on his 500+ cid engine. At that point he will find out that the carb basically stops flowing any additional fuel thru the jets at about a #99 Jet Size. But this was years ago, before all of the Dominator Modifiers got involved. So what was the issue here? Hey, We bought the 3 Circuit Carb and 3 circuits are always better vs 2 circuits right?

Well people I will post up a couple of Pictures of why the Engine Performance "Flat Lined" purely due to the 3 circuit design.

a) All carbs have a Idle Circuit and a Main Circuit in the metering Block and some carbs have a Third Circuit called the Intermediate Circuit which is supposed to help on street cars with Dominator Carbs on them. And it does help on the lower powered engines.

But when you get into the higher powered engines you need more fuel flow thru the metering blocks main circuit.

So here are the Pictures. (Of a "cutaway" Main Circuit on a 3 Circuit Carb.) See anything wrong here?

Tom V.

[Tom Vaught]

So today is an Open Discussion Day for this thread, What do you see in the pictures?

Tom V.