[Tom Vaught]

A bit more today on Holley Carbs.

Mike Urich might have "Written the Book" (books actually) on Holley Carbs but Mike was an Holley Executive Engineer and had time for that kind of thing plus it was good for Holley.

One of the best Holley Engineers (Carb Men) I ever worked with was CHUCK GULLEDGE.
Chuck left Holley, some years after I did, moved to Clearwater, Florida, and opened up CHUCK GULLEDGE Fuel Systems. He mostly built Pro Stock Dominator Carbs for Racers.

I heard about a Dyno Test, run years ago on a Pro Stock Truck engine that was on the dyno.
The carbs were a pair of Holley Dominators built by a company in the northern midwest. Will not go any farther on that deal by providing a name.

So they run the Midwest carbs and they get a number and call me up. I say, what is the deal/
Dyno Owner says, "Tom, the engine seems down on power. I thought it would make more."

So I said" Got any OTHER carbs laying around that you could borrow for the Dyno Test? Braswell, etc? So he says, nope, don'e have any of david's stuff but have tested it in the past and it is good stuff. If I don't try some other carbs the engine will be off the dyno the day after tomorrow."

Then he says, "Hold one, I remebber a older set of carbs under a bench from years ago in some Holley Boxes. Came with the shop when I bought it."
So he looks around and finds the Dominators in the Holley Boxes and pulls one out and sees the Chuck Gulledge tag on the thing. Says "ever heard of that guy?" This is right after Chuck left Holley. So I tell him, blow the carbs off, change the bowl gaskets and bolt them on the engine.
DO NOT TOUCH THEM OTHERWISE.

So he does that, bolts them on the engine and runs a few tests. Calls me back.

Says: Tom, those carbs right out of the boxes were 38 HP better vs the other carbs. I ran the testing several times because I could not believe the numbers and even swapped the other carbs back on and lost the HP I gained from the under the bench carbs.

So I said, you want to make the customer happy, sell him those Gulledge carbs, tell him don't touch the carbs except for gasket changes, and tell him to sell the other carbs he bought to the fastest guy he races against.

Do not know if he did all of that but that truck was kicking butt in that class the rest of the season.

So Mr Chuck Gulledge, not only was a Holley Engineer but also a Top Notch Carb Builder.
You ever find some of his stuff BUY IT! Sometimes who builds the carb(s) can really make a difference and there are GOOD Builders and GREAT Builders
if you catch my drift.

Tom Vaught

[Tom Vaught]

Today I have provided a list of the most common Holley 2-BBLs used for 6-Pack set-ups
These same carbs could be used on a 389 Pontiac Engine (as MOPAR/Holley offered a set-up for the 383 engine
These same carbs could be used on a 440-455 Pontiac Engine (as MOPAR/Holley 440 set-up would work well (especially with Vacuum carbs).

List # Vehicle Year Engine Trans Type CFM

R4144 - 1970 - 440 - Auto - Center - 355
R4175 - 1970 - 440 - Both - Front - 500
R4365 - 1970 - 440 - Both - Rear - 500
R4374 - 1970 - 440 - Manual - Center - 355
R4375 - 1970 - 440 - Manual - Center - 355
R4376 - 1970 - 440 - Auto - Center - 355
R4382 - 1970 - 440 - Both - Front - 500
R4383 - 1970 - 440 - Both - Rear - 500
R4391 - 1969 - 440 - Manual - Center - 350
R4392 - 1969 - 440 - Auto - Center - 350
R4393 - 1969 - 440 - Both - Front - 500
R4394 - 1969 - 440 - Both - Rear - 500
R4669 - 1971 - 440 - Manual - Center - 355
R4670 - 1971 - 440 - Auto - Center - 355
R4671 - 1971 - 440 - Both - Front - 500
R4672 - 1971 - 440 - Both - Rear - 500
R4789 - 70&71 - 340 - Both - Front - 500
R4790 - 70&71 - 340 - Both - Rear - 500
R4791 - 70&71 - 340 - Manual - Center - 355
R4792 - 70&71 - 340 - Auto - Center - 355
R6403 - 1972 - 440 - Manual - Center - 355
R6404 - 1972 - 440 - Auto - Center - 355
R6405 - 1972 - 440 - Both - Front - 500
R6406 - 1972 - 440 - Both - Rear - 500

I will add more to this in a separate post.

Tom V.

[Tom Vaught]

I have included two exploded view illustrations of the Holley 6-pack 2-BBL carbs
(and a Picture of a Holley 950 cfm 3-BBL carb).

The first thing that you will notice is that the old 950 3 BBL carb used a Secondary Vacuum Pod with 4 screws sealing the lid on the pod.
The Holley 6-pack carbs used a 6 Bolt secondary Vacuum Pods with 6 screws sealing the lid on the pod. They are not inter-changable.

The second thing is the 6-pack carbs get their vacuum signal to open the pods from a source in the center carb (like the 3-bbl)
but then use two vacuum hoses to supply that signal to the end carb diaphragms. There is a external nipple on each carb close
to vacuum pod mounting screws. Signal goes from the center carb thru the hose to the pod.

More on 6 pack carbs tomorrow.

Click on images

Tom V.

[ta man]

Merry Christmas Tom...thanks

[Tom Vaught]

If you look on the End Carbs Illustration you will see that the 6-pack carbs had idle mixture screws on the Secondary long before the first 4-Corner Idle 4-BBLs were introduced.

The reason for the mixture screws is because we do not have a common base where we could machine in "Purge Slots" like a 4 BBL on the Vacuum Secondary carbs.
The rare Mechanical Secondary Carbs had a Metering Block and Idle Circuits just like the Primary side of any 2 BBL.

Chrysler wanted to be able to have the same Air/Fuel Mixture to each cylinder at idle with their 6-Pack Manifolds so they did dymo testing (as I mentioned before with the manifolds and tweeked the mixture screws on the end carbs until all of the runners were getting the same Air/Fuel Mixture with THAT manifold.
Then they had Holley set that Air/Fuel Ratio on that List # carb on the flow stands in production. Then they PLUGGED the screws so they could not be adjusted without destroying the plugs/base around the plugs.

Many racers did drill out the plugs and mess with the adjustments for racing, most times making the cylinder to cylinder balance a mess at idle but they were RACE CARBS AND ENGINES! Right. You have to screw with a Holley carb or you are not a racer.
(Have posted before how happy some owners are after I put the calibration back to stock Holley settings. So that is why the plugs and mixture screws are there.

Tom V.

[Tom Vaught]

I mentioned the Vacuum Diaphragms used on the 6-Pack (and 435 HP Corvette) engines as having 6 screws to hole the cover on the Housing that bolts to the carb main body.

The 6-Pack Diaphragms are still out there in service but the old 3 BBL carbs 4 screw diaphragms have not been available in many years.
BUT you can mod a 6-pack diaphragm to be used in a 3-barrel by cutting the diaphragm (using a hole punch to match the 3 BBL mounting holes.
That is the easy part.
You also have different length stem peaned on the diaphragm and its washers. But if you remove the old 3-BBL stem, cut the 3 BBL stem down so that you have a new length to pean over the washers, it then will go right into the 6-Pack diaphragm and be close enough it length to work fine.
You put the 6-Pack stem hardware in a carb parts tray.

So to summarize,
1) Trim the ears off the 6-Pack diaphragm but keep the sealing surface so it can be glued to the 3-BBL housing.

2) Remove the original 6 pack diaphragm's stem and put it away in parts.

3) Modify the original stem from the 3 BBL to go on the new trimmed 6 Pack diaphragm.

Assemble the parts in the 4-Bolt 3-BBL housing and you are good to go with your now working again 3 BBL carb.

Tom V.

[Tom Vaught]

Two other quick comments for tonight.

1) The 3-BBL Vacuum Diaphragm Stem is about .700" LONGER vs the 6-pack Vacuum Diaphragm Stem.
You can't add material to the 6-Pack stem to gain .700" additional length (splice in a section) because the hole thru the vacuum housing that bolts to the carb is not that large and the stem travels in an arc as it opens the throttle blades.

2) So the correct method is:
Grind off the old peaned over stem metal.
Create a new stem (using a lathe or careful filing.
install the new stem thru the 1st washer, thru the 6-Pack diaphragm, thru the 2nd washer, and then with everything in place pean over the new stem over and you are done.

Sounds confusing but a simple inspection of a vacuum diaphragm, makes it very clear.

Tom V.

[Tom Vaught]

I was tired last night.
In simple terms remove the metal rod from the old 3 barrel diaphragm, mod it so it can be repeaned on the 6-Pack diaphragm.
Install it and the two metal discs on the new 6-Pack diaphragm and repean it.

Tom V.
More later.

[Formulas]

Tom i have a 1050 3bbl. I was under the impression that if my diaphram ceased ops. I could use the more mainstream vacum housing is that not so?? Of course opening rate would have to be recalibrated as the larger diaphram will have more force at lower vacum siginal

[Tom Vaught]

A bit more on 6-Pack carbs and 3 BBL Carbs.

The first Holley "Tri-Power" systems for the Big Block Chevy Engines was offered in 1967. I have a Hot Rod Magazine Cover picture somewhere (1967 time frame) with a prototype set of carbs mounted on the BB Chevy Engine. This was taken before the final casting design was put into production for the Corvette Engines.

In 1969, Holley offered the 6-Pack carb set-up on the MOPAR vehicles. Basically the same set up as the Corvette.

So now we come to the first technical point for the day. I have attached a picture showing the two metering plates offered on the secondary carbs. The Rectangular Plate being the early plate (from 1967 to 1969) and the "second design" plate (with the angled lower edge plate, see picture). They are not interchangeable. So if you have early carbs some of the Hot Rod (aftermarket) plates with removable jet capability may not work and you will be wondering why. See aftermarket plate pic.
It has the shape of the 67 style plate but is really designed for the 4 BBL vacuum Secondary carbs. More on 6-pack and Corvette 2 BBL carbs later today.

[Tom Vaught]

Many People, including myself, like a carbed engine that senses what the engine actually wants for airflow and gives it just that much.
I have a couple of 850 Vacuum Secondary carbs that are a exceptional on a road vehicle.
Same deal applies with the 6-Pack Vacuum Carbs except that they can support more airflow thru a larger engine.
Simple Math: Center Carb airflow = 355 cfm @ 3" Hg test pressure. To get to 4 BBL test pressure flow multiply the 2 BBL cfm by .707 or
355 x .707 = 250 cfm (4 BBL Rating).

Same deal for the end carbs:
500 CFM x .707 = 353 cfm for each carb and two carbs so 707 total cfm for the 2 end carbs.

So 707 cfm plus 250 cfm = 957 cfm (same as our 3-BBL Holley carb) but a lot "Cooler" looking package. Both set-ups should run about the same times on the track (if dialed in properly) as they are both Vacuum set-ups and they have 100 more REAL CFM vs the Corvette 850 CFM Vacuum Carb. Holley did stuff for a Reason.

Tom V.

[Tom Vaught]

In my next post I will describe the parts required and the mods necessary to install Vacuum Secondary 6-Pack carbs on your 1966 Pontiac Tri-Power Manifold.

1) You need to order 3 of the adaptors in the link below so that you can mount your vacuum carbs to the Pontiac Intake. They are $40.00
each. You can buy cheap chinese adaptors from Speedway for $15.00 each but the quality difference is apparent.
http://www.dashman.net/product.html?id=245

(Dashman also shows you a pic of the adaptors on the pontiac intake).

2) So now you have the Holley Carbs, the Intake, the Intake adaptors, and are now ready to move on to the Fuel line fabrication and vacuum hose routing on the passenger side of the engine. I have provided a Picture of a MOPAR engine so you know what the fuel lines look like and the vacuum hose routing looks like.

Finally you need to install the safety linkage to manually close the secondary throttle on the vacuum carbs when you let off on the gas.

The fuel lines needed to be longer and of course the safety linkage also needs to be longer so some fabrication is required.
The links have to be cut and additional length added to them for the wider spaced carb position.

Looks at the pics and you will see what I mean. (I just cut the two links and added a piece in the middle of each one to make it longer).

Tom V.

[Tom Vaught]

One thing I just noticed on the Vacuum Hose Picture I provided. The vacuum hose from the metering block to the distributor can easily be seen. The hose connection to the center carb main body is hidden. Will try to scrounge up a clear picture on that connection.

OK Found a decent picture.

The nipple on the metering block is the upper nipple (it is pointing slightly upward and to the right).
The nipple for the signal to the secondary carbs can be seen on the main body and it is pointing slightly downward and also to the right.

Tom V.

[4zpeed]

Is that yours Tom?



That looks absolutely delectable. an Christmas is jus roun the corner!

Then again that little fat bast, ur a, presious lil feller, never leaves me nutten that cool.
.................................................. .................................................. ......................................

Maybe I could coerce, um, I mean converse with him since I've been mostly well behaved this year.

Been attending class all along with great anticipations of saving money... little did I know...

I'm going to try and stay the course for now though as I have my 400 rebuilt and a 3310C still in the box.

I'm assuming with the newer "High Location" Idle Feed Restrictions I may want to revisit that post at some point.

Appreciate the tempt...uh, technical data.



Frank

[Tom Vaught]

That picture is of a Factory 6-Pack Intake and the Holley carbs installed. Used to show the linkage for the Positive Throttle Closing links.

There is a Thread out there called "For historical purposes" (in the Tri-Power Forum that shows my intake system The BG Intake is not nearly as tall (more stock Tri-Power Height).

Tom V.

[Tom Vaught]

A story on 3-BBLs.
Many, many years ago I was helping Marty Palbykin on his NATURALLY ASPIRATED 1971 GTO. 470+ CID engine
850 CFM Holley Carb, Tilt Front End for easy maint on the vehicle and light weight on the front end.

So Marty decides that he wants to try more CFM on the engine. So we talk about installing a Holley 3-BBL on his car
(a REAL 100 cfm increase in airflow to the engine).

Marty is good with that deal but he says he wants the 3 BBL to be a Double Pumper Carb.
Not a Old School modded (660 center squirter Mechanical Linkage) single shooter removed
and 4 tube shooter installed.) Nope not going to make it. Has to be a Double Pumper 3 BBL carb.

So a Very Good Machinist Friend, Bill Klausing and I decided to build a 3 BBL Douple Pumper Carb
from a 850 Double Pumper Carb that already had the front and rear pump shooter bosses cast into the mainbody of the carb.

Installing a 3 BBL Throttle Blade was easy enough, just a bit more work in the center of the base
and using the same Double Pumper Throttle Shafts.

But now the metal needed to be removed around the rear Power Valve area and that void plugged
with a plug and a two part metal epoxy bonding process. So we did that deal and it looked great.
No need for a rear power valve on a Race Carb.

So we give the carb back to Marty for testing.
Primary works great as it should. Secondary operation was poor (being kind).

So I get the carb back and have it flowed on the Holley Flow Stand and the air/fuel is ok on the
rear but there is a giant lean area between the two rear boosters. So another Carb guy says:
"That is why the boosters are moved inward on a 3 BBL carb, to remove that lean spot in the center of the rear fuel distribution to the manifold.
Got to do that or the rear distribution is bad."

Well we previously found that deal out Bubba. I laugh at the carbs I see in the internet with the
two 3 BBL blades vs the normal 4 throttle blades and bragging about massive cfm increases with
their carbs. Been there done that .

So we need to have the boosters in the 3 BBL spots for the right mixture in the manifold.
1050 carbs use copper tubes to feed the fuel into the secondaries. Might have been easier
to try those (thinking about it today) and more cfm capability but we did modded conventional
boosters (moved to the 3 BBL locations. More metal Epoxy and then more flow testing.

But the mod worked. We retested the carb on the Holley Air Stand and the distribution was great on the rear
of the 3 BBL prototype "Double Pumper". So Marty ran the carb until he decided to go with Boost and then
the carb went to someone else I think.

Marty did say that he thinks with the converter he had that now we really did not need that pump shot on
the secondary side. Thanks Marty (;>( LOL!

So my points are:

1) Holley put the boosters where they are on the 3 BBL (secondary side) where they are FOR A REASON.

2) Holley did not put a shooter on the secondary side of the 3 BBL when they stayed with a Vacuum Secondary
carb (for a reason).

3) The Hot Rod Guys made the 4 shooter kits for the 3 BBL carbs (converted to mechanical secondary operation)
for a reason.

4) Center Squirter carbs and Double Pumper carbs were created because of the work and knowledge learned from
the 3 BBL carb mods and other mods before that time.

Mechanical secondary carbs need pump shots vacuum Secondary carbs can get away without a pump shot on the secondaries.
Big secondary carbs or Four (2 BBL Dominators) need big pump shots when installed on big plenum manifolds.

So now you know a bit more about the 3 BBL story.

Tom V.

[Tom Vaught]

Today I am going to talk a little bit about magazine articles, and a couple of comments about the people who write the articles.
Anyone can write an article or a post but you really want to pay attention to the actual information inside the articles.

I found two decent articles (as an example) about a Holley Tri-Power System (offered for the SB Chebby engines).
Each writer took a different approach on how he wrote the article.
One article used a dyno test and the second article provided information. So you would might assume that the Dyno Article was
a better article. I will provide the links to the articles and let you read them vs go over every picture etc.

Magazine Dyno Tri-Power Article:
http://www.hotrod.com/articles/testi...-power-system/

Web Tri-Power Article:
https://www.racingjunk.com/news/2015...-power-part-1/
(There are 4 parts and 4 links easy to use).

So the assignment for the day:
1) Two Articles by different writers on the same basic subject.

2) Both writers took pictures of the parts.

In the 1st article the carbs were the basic shiny silver Holley stuff from Summit/Holley.

In the second article the carbs had the Dichromate finish.

In both cases, some basic carb math was done to come up with a cfm for the 3 carbs.

So read thru both articles and judge who you think you should pay attention to when discussing carb information. Enjoy.

I will add my comments later

Tom V.

[Tom Vaught]

I will let you people think about this one until tomorrow and then go thru the articles.

Tom V.

[4zpeed]

Tom V
That picture is of a Factory 6-Pack Intake and the Holley carbs installed.

I've seen your BG intake and carbs, very nice indeed, but I thought you may be toying with a new project in your retirement.

BTW that Ford 6V open plenum intake looks like it would perform very well.

I'd love to build a Holley Tri Power setup but with the EFI's and other systems out there I doubt a economical post 66 intake will ever materialize.


Thanks for the eye candy,

Frank

[4zpeed]

The Racing Junk article is by far the most informative and in depth, also gives a simple formula to convert a 1.5" Hg depression test to a 3".

Great explanation on compatibility with common Holley parts, detailed breakdown of components with dimensions, descriptions, photos, "uber cool" way of presenting material but of course obviously and most important accuracy of information!

Now I see how easily the accuracy as well as integrity of information can and does get compromised, then readily accepted by the novice Rodder such as myself.

Had it not been for my attendance at Tom V's Holley School Of Thumb I would have never given it a second thought an took it for gospel. Thank you Tom!

The article from Racing Junk exposes the improper comparison by Hot Rod's columnist between the 750 CFM Holley vs. the so called 1,025 (in actuality 725) CFM Tri Power set up.

As you have stated in this thread...

Racing Junk
A two-barrel carb is tested (for flow) at 3" Hg depression. On the other hand, four-barrel carburetors are flow rated at 1.5" Hg depression. These are the industry standards for carburetor airflow testing.
◾1025 divided by 1.414 equals 724.9 or, 725 CFM.

On the other hand you have this...

Hot Rod
If our math is right, that totals an overkill of 1,025 cfm,
◾325 + 350 + 350 = 1,025 CFM

To compound the misinformation further and misfortune to others...

Hot Rod
Don’t stress over achieving a 100 percent opening of all six barrels—with over 1,000 cfm on tap,

To reiterate, physics do not change, on the other hand, you can play with numbers...


As always Much Thanks

Frank