[Tom Vaught]

No Comments? I will give people more time on this one.

Tom V.

[Tom Vaught]

Ok, Time I guess to explain Picture #1 and #2 in Post # 159.

The pictures show a typical 3 Circuit Metering Block with the left Main Well wall machined away. By doing this now anyone can see that there is a new part installed in the normal empty Main Well. The part installed is the Emulsion Tube and Idle Feed Restriction for the Idle Circuit of the 3 Circuit Dominator Carb.

So if you have a street car and want the Dominator look, Holley came up with a way to package the Idle Circuit, Intermediate Circuit, and the Main Circuit in the normal 2 Circuit Metering Block carb.

But you can also see that the Idle Circuit now takes up a bunch of space in the normally empty Main Well. So on the street and some spirited racing on the track the carb functions fine.

But put the carb into a true race mode with large jetting requirements, "We have a problem NASA"
(The Idle Tube acts as a restriction in the Main Well and blocks additional fuel from going to the engine once you get past about a #9 Holley Jet.
You can take the Jet completely out of the well and it will not make any difference as the Idle Tube is downstream of the Main Jet and is the controlling restriction in the circuit.

So what do Holley Dominator Carb Builders like Shaker455, Tuner, MarkAudio, and myself do?
We convert the carbs back to Two Circuit carbs.
No restriction in the Main Wells, plenty of fuel even on an alcohol carb, and the carb is designed for Racing, not street manners.

So every Guy who bought the 3 Circuit Carb vs the "plain" Two Circuit" carb just put a carb "Throttle Stop" on his racing package if he bought a Holley Dominator 3 circuit carb.

Now IF the carb was a Custom Built deal from Beaswell, etc with custom Everything then maybe you still can make a 3 circuit carb work. Just don't expect the normal Jegs or Summit deal to work for you. Holley just tried to make the street guy happy with a Dominator.

Tom V.

[Tom Vaught]

The Jet number should be #99 jet, not #9, got a new keyboard for Christmas, really nice but the keys are sticky until they break in a bit.
You could get more fuel if you use the Power Valves in the carb and the #99 jets but some do not like that deal.

Tom V.

[4zpeed]

Originally Posted by Tom Vaught

"We have a problem NASA"

LOL!

Originally Posted by Tom Vaught

What do you see in the pictures?

Looked like a Hot Rod carpenter with a 6 penny nail trick, but I wasn't about to throw that out there.

Should be a donation box around here for that keyboard, glad somebody was thinkin bout us, I mean you.


Much Thanks,

Frank

[Tom Vaught]

Thank You Frank. Happy New Year.

There are some good carb people out there who can make a 3 circuit carb into a 2 circuit carb so your hard earned dollars are not totally lost.

One guy out of 200 purchasers of 3 circuit Holleys needs that mod. Most times he will be a boat guy with Large twin engines, Dual Dominators on each engine, possibly a supercharger under each set of carbs.

Takes power to run fast on the water with a long hull boat.

But THAT is why the engines quit making power sometimes with what you think would be over-kill in carbs.

Tom V.

[Tom Vaught]

Since Mr Ken Crocie brought up the 8156 Double Pumper Carb in a post, I will add some additional info on that carb.

Here is a Link to the #8156 750 CFM Double Pumper Carb.
A Post by "Tuner" (He goes by Yeti) on the Yellow Bullet Forums)
http://www.yellowbullet.com/forum/sh....php?t=1321578
"The 8156 came out in 1978 and is essentially a 4779 double pumper with four corner idle. It was the first four-corner-idle double pumper Holley produced. Original jet size is 70P & 83S. Should work OK on a T-Ram."
This link shows a nice picture of the Johnson Linkage
https://books.google.com/books?id=_f...s-8156&f=false

The carb was a 750 CFM carb as mentioned by several people. It used a 70 Primary Jet and a 83 Secondary jet. It used a 6.5 Power Valve on the Primary side of the carb. It had 4 corner Idle, (IT WAS THE VERY FIRST 4 CORNER IDLE HOLLEY CARB, I worked on that carb in 1977). It used a .028 Pump Shooter on the Primary and a .031 Pump Shooter on the Secondary. It had the normal 1-3/8" Primary & Secondary Venturis and the normal 1-11/16" Throttle Blade Base Plate.

The 850 CFM version of the carb was List #8162.

You can see the Johnson Linkage and how the linkage was much more complicated with the cam slot mounted on the primary lever (with a horizontal slot vs the 660 center squirters vertical slot), the pivot/roller on the main body, the link from the pivot to the secondary throttle lever, the cut off airhorn (production) and the 50cc Pump system sometimes installed on the Primary side of the carb, like a 660 center squirter carb. The pic shows the small pump.
The carb had a normal Power Valve on the front and a blocked PV on the Secondary block.
The front metering block number is 8542A, the Rear Metering Block is 6541A. The base is 12R-112-32.

Tom V.

[Tom Vaught]

The 8156 race carbs were very good carbs.
Ken Crocie (of HO RACING fame asked about building a 8156 type carb again.
How much interest do you think there would be for a carb like that?
Post open for discussion on this topic.

Tom V.

[4zpeed]

From what I understand the 8156 would be a very good street carb for the performance minded, provided it's used in a automatic tranny application.

Could you give an example of what one could expect to use it on straight out of the box as far as specs.

I think its safe to assume most with performance in mind are building 455's or stroker's these days but I don't want to exclude the 400's or guys that want that radical 350.

Edit: Reason for asking is I don't modify much and perhaps there are others that would prefer a out of the box product.



Thanks,

Frank

[Tom Vaught]

8156 was a "bolt-on" circle track carb for many non professional "hobby" racers in the late 70s and 80s. You could pretty much "bolt on "that carb on a 350/355 cid small block chebby engine and be competitive at the local race track.

That being said with a simple jet change you could put that carb on a Ken Crocie Pontiac Engine and be happy with the results.

I do not consider jet changes as differing much from "out of the box" as there are many engine displacements and engine combinations and Holley did a great job on designing a carb that for the most part worked very well with just a simple jet change.

Tom V.

[4zpeed]

Tom V
"I do not consider jet changes as differing much from "out of the box""

Maybe not for you Tom, but anything I do besides bolt it on is a mod for me , although a simple jet change is highly acceptable, been there, and can now dabble in other areas thanks to your thread here.

After jets the only reason I ever dove into a Holley was to rebuild it, and the jet change was for someone else, I always used the 780 CFM vac 2nds right out of the box, worked great.

OK, so an accurate statement would be, with a simple jet change the 8156 would be a perfect carb for any moderate to high performance street 350-455, given the CFM requirements were not exceeded?

If so from what I have read (Tuner) and the information you have given here, one would think it would be a highly desirable carb, being that you have mentioned the newer 4779 is lacking in design.



Frank

[Tom Vaught]

Originally Posted by 4zpeed

Tom V
"I do not consider jet changes as differing much from "out of the box""OK, so an accurate statement would be, with a simple jet change the 8156 would be a perfect carb for any moderate to high performance street 350-455, given the CFM requirements were not exceeded?

If so from what I have read (Tuner) and the information you have given here, one would think it would be a highly desirable carb, being that you have mentioned the newer 4779 is lacking in design.



Frank

Lacking only in TOO MANY COOKS IN THE KITCHEN WHEN THE 4 CORNER IDLE 4779-6 AND LATER 4779 DPs WERE CREATED.

But you are spot on as usual.

Tom V.

[4zpeed]

Originally Posted by Tom Vaught

Lacking only in TOO MANY COOKS IN THE KITCHEN

Tom V.

LOL

Thanks Tom, in lieu of lacking, perhaps a more accurate statement along with your description would have been over designed.

Furthermore, from Kens signature "Good Ideas Are Often Found Abandoned In The Dust Of Procrastination" on the other hand over baked!

I would venture to say that if Mr Ken Crocie were to reintroduce the 8156, there would be considerable interest, not only from the Pontiac crowd but many others due to this burnt product.


Frank

[Tom Vaught]

And if he personally wanted to reintroduce the carb to customers, I would be happy to provide info on what it would take to get there.

Tom V.

[Tom Vaught]

Today I am going to throw some SERIOUS CARB THEORY at you.
If you are not interested in that area of carb tuning, see you tomorrow. Tom V.


Tuner: “On carbs it's very important that the correct two-phase flow gets established during emulsion. Otherwise you will see RPM dependency of AFR.” I see your remark as a profound understatement. Incorrect two-phase flow is at the root of all this aggravation.

People who have drill bits but don’t know why to use them have been molesting innocent carburetors for a long time. Now some of them are in charge of the manufacture of new carbs and they think they have improved them by using larger drill bits to make the air bleed and “emulsion” orifices. I guess the guys that engineered the original carburetors on the old muscle cars were pretty stupid or they would have “improved the emulsion” 40 or 50 years ago when they had their chance.

Basically TUNER is saying that after the mid 80s the people from Holley went other places and the BASIC Knowledge was lost. Marvin Beniot (later Quick Fuel Owner), Chuck Gulledge, Louis Lucas, Steve White, Marty Brown, Jeff Komar, were all old school Holley carb people. The new guys that went to The south (with Holley Aftermarket, basically were unable to do the job and the company went banklrupt the FIRST TIME. (They went bankrupt several times). TV

TUNER: It is well documented that introducing air into the main well encourages low signal flow and can encourage or discourage high signal flow. The natural characteristic of a plain jet and nozzle (no air) is to get richer as airflow increases. The purpose of the air bleed system is to modify that behavior to accomplish a constant (or the desired) air/fuel ratio over as wide a range of airflows as possible. The particular ratios for power and cruise are realized by the selection of jet and rod or jet and auxiliary jet (power valve channel). The purpose of air bleeds is not to emulsify but to accomplish the correct fuel delivery. Emulsion is just a beneficial side effect.

This is a very true statement That is why some CARB PEOPLE call the Air Bleeds "AIR CORRECTORS" TV

What I’m going on about here is Klaus’ remark about “correct two-phase flow”. That is the description of a fluid flow that is made up of a liquid and a gas flowing together in the same conduit. As the ratio of gas to liquid increases (more gas, less liquid), at some point the gas bubbles coalesce from many small ones into a few big ones and the flow starts to “slug” and become erratic. The carburetor nozzle spits like a garden hose with air in it when there is too much “emulsion” air.

An emulsion of air and fuel has reduced density, surface tension and viscosity compared to fuel alone. This increases the flow of fuel considerably, particularly in low-pressure difference operation, at low throttle openings or lower engine speeds. Just how much of an increase (richer) is dependant upon where and how much air is introduced into the fuel flow.

Mainly, what must be understood is that because the fuel discharge nozzle connects the venturi to the main well, whatever the low pressure (vacuum) is in the venturi, it is also the pressure in the main well. The air bleed is in the carb air horn or somewhere else where it is exposed to essentially atmospheric pressure, which is higher than the venturi pressure. This pressure difference causes air from the air bleed to flow through the emulsion system into the main well and to the nozzle. The flow of air can have very high velocities, approaching sonic in some orifices. The airflow literally blows the fuel toward and through the nozzle. A larger main air bleed will admit more air to the emulsion system and that can increase or decrease fuel flow to the engine. The size, number and location of the other air holes in the emulsion system, the size of the main well flow area, the size of the nozzle and the specific pressure difference at the moment are the determining factors. The ratios of air volume to fuel volume to flow area, with the air volume's expansion with the venturi velocity induced pressure reduction being the key. The bubbles expand as the pressure drop increases with airflow.

The fuel flow through the main jet is the result of the pressure difference between the atmospheric pressure in the float bowl and the venturi air velocity induced vacuum acting on the nozzle and the main well. The venturi vacuum in the well is reduced (the pressure is raised) by the "air leak" from the air bleed. This reduces the pressure difference that causes the flow through the main jet. If the air bleed were big enough, the pressure in the well would be the same as in the float bowl and no fuel would flow. Think about drinking through a soda straw with a hole in it above liquid level. Bigger hole, less soda. Suck harder, not much more soda. Big enough hole, no soda. This is the means by which the emulsion system can "lean it out on the top end". Incidentally, the vacuum that lifts water up a soda straw is in the most sensitive operating range for emulsion systems.

It is in the lowest range of throttle opening, at the start of main system flow, that the effect of adjusting the introduced emulsion air (and it's effect in increasing the main fuel flow) is most critical. Small changes can have large and sometimes unexpected or counter-intuitive consequences. The goal is to seamlessly blend the rising main flow with the declining idle/transition system fuel delivery to accomplish smooth engine operation during opening of the throttle in all conditions, whether from curb idle or any higher engine speed. The high speed and load mixture correction is usually easily accomplished, in comparison.

The vertical location of the bleeds entering the main well influences the fuel flow in the following ways.

1: Orifices above float level or between the well and the nozzle allow bled air to raise the pressure (reduce the vacuum) in the nozzle and above the fuel in the well. That delays the initial start of fuel flow from the nozzle to a higher air flow through the venturi and is used to control the point in the early throttle opening where the main starts.

2: Orifices at float level increase low range (early throttle opening) fuel flow by carrying fuel with the airflow to the nozzle.

3: Orifices below float level increase fuel flow by the effect of lowering the level of fuel in the well to the hole(s) admitting air. This is like raising the float level a similar amount (increases the effect of gravity in the pressure difference across the main jet) and also adds to the airflow carrying fuel to the nozzle. Locating the orifices at different vertical positions influences this effect’s progression.

4: The "emulsion holes" influence is greatest at low flows and the "main air bleed" has most influence at high flows.

In the first three cases above, once fuel flow is established it is greater than it would be with fewer or smaller holes. Visualize wind blowing spray off of the top of water waves. It doesn’t take much pressure difference to cause the velocity of the airflow through the bleed orifices to have significant velocity in the orifice, even approaching sonic (1100 F.P.S.) if the orifices are small. The phenomena of critical flow is what limits the total air flow through an orifice and allows tuning by changing bleed size.

Essentially, the emulsion effect will richen the low flow and the air bleed size, main well and nozzle restrictions will control the increase or reduction of high flow. Again, the desired air/fuel ratio is the primary purpose of the bleed system. "Improved emulsion" is an oxymoron if the modification of air bleeds to "improve emulsion" results in an incorrect air/fuel ratio in some range of engine operation. Correct proportioning of all the different bleeds (and, of course, the idle, transition and power circuits) will give the correct air/fuel ratios over the total range of speeds and loads and a flat air/fuel ratio characteristic at wide open throttle.

A little simpler, the airbleeds and emulsion are used to set the fuel curve in a Holley. The 3rd e-hole will make it a little more active at the low end, and possibly a little lean up top depending on the main air bleed used. If you look at the 2 circuit conversion thread, you can set your 8082 metering up at the starting point in the thread even though it is already a 2 circuit carb. After that you HAVE to adjust the metering for your engine as to what it wants to get the best performance, but in most cases it will be close. Your iron head 468 is no different than some of the other combo's here, everything from milder small blocks to some killer engine., Unless the combination is bad, poor cam design or the ICL is way off, timing is way off, plugs are too cold... etc, it should be close enough to start with. Learn to properly read the plugs and invest in a wideband O2 if you can, it will help you find the most out of it.

Tom V.

ps I did not feel like typing all of this stuff in my words when TUNERS were most likely would say it better. Tom V.

[Tom Vaught]

Going to let this "soak in" for a couple of weeks and then get back with more info and comments.
Maybe talk about Boosted Carbs: Draw thru and Blow Thru Holley Carbs for Pontiacs.

Tom V.

[ta man]

Thanks again Tom! You have more detail than my Holley books. In the future when the "copy and paste" experts are spouting "their" knowledge...much of this will be reposted...and for sure they better have your name mentioned!

[KEN CROCIE]

Can't wait for the blow thru discussion!
TV: we're going to need another curbside chat soon.

[Tom Vaught]

Over a Period of 4 Hours, I think we invented the term, Ken. Lincolnshire GTO Nationals was one of my best memories.
The Virginia Discussion was ok but the Illinois Discussion was the best.

I will PM you my Phone Number or you can just call Craig and he will give it to you. (If you do not have it already.) New Phone etc.

I may change my thinking and post about Fuel Pressure Regulators for Blow Thru Carbs today.

Thanks Ken.

Tom V.

[Tom Vaught]

Per Mr ken Crocie Request, a Discussion and transfer of information on the Holley "Blow Thru" carburetor and its modifications

Basically we will break it down to several steps and recommended components for the individual steps.

First step is you need to have a clean fuel tank/fuel sock pickup or a Clean tank and internal fuel pump (obviously with its fuel sock installed).

[STEELCITYFIREBIRD]

A Whole LOT to absorb Tom.
It seems you weren't ready to retire yet, but possibly? ready to move on to publishing??