[Tom Vaught]

Most Holley 750 cfm 4779-1, 4779-2 thru 4779-5 were TWO Corner Idle carbs.

Same deal for the Holley 4781 850 cfm early carbs.

The carbs did have a pair of tiny fuel discharge holes under the transfer slots on the secondary side of the carb to let a bit of fuel get purged from the secondary fuel bowls if the owner was not opening the rear throttle blades constantly.

So then about Holley 750 4779-6 Holley added the 4 corner idle circuits to allow using a common metering block on the front and the rear of the carb to make more fuel flow thru the rear idle circuits of the carbs.

The OLD setting on a carb for the primary 2 corner idle mixture screws was 1 and 1/2 turns out from seated. The 4 corner carbs spec was 3/4 turn to 1 turn out for those carbs. Supposedly this helped the fuel distribution in open plenum Holley Intakes. The total idle fuel supplied to the engine was the same in both carbs.

The only Throttle Blade adjustment is to set the Front Primary Blades so that you have a square window when you look at the carb from the bottom and the Primary Transfer Slot. Then you never touch that idle speed screw on the base plate again.

The secondary blades need a slight modification. You make sure the blades are centered in the bores when closed and then you flip the secondary throttle blade "stop screw" so
that you can adjust it from the top. Screw Driver "slot" now goes on top (pointing at the sky) and you can adjust the secondary blade position to get the best idle rpm for your engine. Most times you can leave that screw alone too. So from now on THAT SCREW is what sets your Idle RPM.

Hope this helps.

Tom V.

[GTO-relic]

that's cuz BG had released stuff like this....
750 baseplate with 2 different venturi sizes,
850 baseplate with 4 different venturi sizes
850 baseplate with 2 different venturis, and annular boosters.
that's only one line, the GC RS
general competition, removable sleeve

there also was Drag Race DR, Road Race RR, Tunnel Ram TR, Oval Track OT, Blower Carb BC lines, and 4 Alky lines.
fixed venturi, or removable sleeve.
a total of 80 different RACE carburetors, using 750/850 baseplates, all custom tailored metering to specific engine combinations, based on CID, cam timing, compression.
650-1050 cfm range
Holley wasn't even on the same floor, or in the same building as BG.
in addition, there was the King Demon Dominators, and Road Demon/Street Demon carbs with traditional choke horns.
every tuning spec was published for easy reference, for every single carb.

[64gp4spd]

Thank You Tom, really appreciate it

[GTO-relic]

the entire Demon line was basically custom carbs,
calibrated and metered based on CID, cam specs
something Holley only did on a very limited basis.

[Tom Vaught]

Glad to help and this way the carb can operate with a fixed calibration at idle, and off idle basically the same (day after day) and you never "Lose the Rabbit" (constantly playing with a group of circuits) that rarely need to be changed for low speed operation.

Tom V.

[Skip Fix]

Here is an article I hung on to from college-found it in a box at my folks house. Modifying 4224s. Tom can give some input on his thoughts. Boy Hot Rods had freaking 205 pages back then!!

[Tom Vaught]

I HAD THE SAME MAGAZINE ON THE SHELF FOR YEARS, But,
a very good Holley Friend is putting together a Magazine "Library"
in the upper floor of his "Barn" (actually a very large storage building)
that can park 19 vehicles inside on the bottom floor and has a lot of
storage space on the upper floor where the "Library" will go.

So far I have transferred about 12,000 magazines to his library with the earliest ones
being from the 50s and the latest ones 2021. They were all of the magazine published
magazines: Hot Rod, Car Craft, Super Stock, The Pontiac magazines, the Ford magazines, all of them.

But glad he can make use of them.

The Paul Bevins article on the 660 Center Squirter Carbs is right on, except for years I replaced the rear metering plates (carbs mounted sideways) with regular jet-able
metering blocks and used the "Race Bowls" vs the "Side Hung" fuel bowls.

Thanks Skip for posting the article. You could mount your carbs in the normal North/South manner on your special cross-ram intake.

Tom V.

I still have I think 3 sets of those carbs on the shelf.

[Tom Vaught]

I ran across a post from the Dominator Board I used to post on with Tuner and Markaudio from years ago.

The specific Dominator is a 3 circuit carb that was modded back to a 2 circuit carb.
Jeff (the carb guy from the Pontiac board) has done several of the 3 circuit carb to 2 circuit carb conversions. I would recommend him for the conversion as he may have some Pontiac specific mods above and beyond what I am going to post below.

Here is the information:

Hey guys,im setting up a holley 9375 dominator for a friend and doing the 2 cicuit conversion like i did on my 1095 king demon.
This is for a 496 c.i chevy bigblock with afr heads and a [email protected] cam with .695 lift.

My question is this.My 1095 demon has the idle eze feature i installed for idle air.This holley does not.
Should i be drilling throttle blades for some idle air?Or should i try it without them first?

I set a set of 4150 proform blocks and carb as follows for the 2 cicuit conversion:
IAB=.070
HSAB=.026
T-JETS=.063
EMULSION HOLES 1&3=.026
EMULSION HOLES 2&4=BLOCKED
ANGLE CHANNELS=.161
KILL BLEEDS=.028
IFR'S=.036
PRIM PVCR=.089
SEC PVCR=NONE
PRIM PV=3.5
SEC PV=BLOCKED
PRIM JET=85
SEC JET=93
SQUIRTERS=42
PUMPS=50CC
CAMS=YELLOW

This is the recipe i have on my 468 pontiac that works great.Only difference is the idle air. Should i drill throttle blades on this holley since it dont have idle eze feature?

It's been my experience that holes in the plates are only needed if you can't get enough air without over exposing the T-slot.
My Dominator has .040 slot exposed with the blade shut. So, I had to get some air without exposing any more slot.

Remember this info: As related to the transfer slot, everything below the butterflies is fuel, every thing above the butterflies is an air bleed.....as you open the butterflies your adding more fuel but reducing the air...

Personally I would play with the IAB and IFR before drilling any holes in the blades...and maybe open up the TSR if you do drill holes then you may need to adjust (or remove) your "Transfer Slot Restrictor" size....

A few Dominator carbs have a bunch of slot exposed below the blade with the blade 100% closed.
You try to open the blade for curb idle air you expose more slot.
The fix is to leave the blade 95-99% closed (100% will stick) and add curb idle air either by drilling holes through the blades or on race apps by bleeding air through the air filter stud boss.

This specific Dominator needed .040 slot exposed below the blade with the blade shut. .060 holes in the blade were added with good results.

Feed-back from the guy working on the carb:
There is no t-slot exposed with blades 100% shut.
I have the butterflies adjusted to expose .020 t-slot back and front.
I put the carb on yesterday and it did need some more idle air.
I drilled .070 holes in blades and it worked perfect.
Still have only .020 t-slot showing.
The idle screws are out 1 1/4 turn and responsive.

The motor seemed to love the starting recipe i gave the carb as a 2 circuit. All I did was turn out idle screws 1/4 turn and drill blades with .070 holes.

So there you have the post and the info we provided to him.

Tom V.

[GTO-relic]

quote:
"Barry Grant started that inflated cfm number crap years ago. Well Barry is gone, Holley owns his company and his carbs, and the cow is out of the barn. "

whoever posted this, you need to do some research.

BG Demon carbs were wet flowed at 1.5" HG/20.4" water. The corresponding DRY FLOW number would actually be approx. 7.6% more than what BG rated them at, compared to a Holley, because Holley DRY FLOWS their carbs for rating. BG also gained 6% discharge coefficient for the patented scalloped air entry on the Race Demon carbs at that time, compared to a Road Demon/Street Demon with a choke horn on it. the BG owned Demon Carb. company put their test specs in writing, it's on page 44 of the Demon Carburetor manual.

so, right off the bat with an "old" vintage BG-era Demon, you can add 7.6% to their stated flow rating, and also get a 6% better discharge coefficient for then-patented scalloped entry, compared to a POS Holley w/choke that now costs $1 per cfm new. This is why used Demon carbs are flying off Ebay and Craigslist lately like hotcakes for $250-$400 each, and new Holleys are sitting with no bidders or buyers at $500-$800+. The fact that many new Holleys have Chinese, Mexican, etc. parts, and the ones still made in USA have very poor finishing QC, isn't helping matters any- Holley is now a holding company owned by people who don't even like cars, they just want ROI, and aren't even Americans, and would like all our cars crushed, and for us to go electric across the board. wake up. the NWO corporate money grabbers are in our hot rod kitchen. they now own it.

so...BG wasn't flowing carbs at 28" water, and inflating numbers. He was wet flowing at 1.5"HG/20.4"water and advertising REAL numbers. He even used fluids in the flow tests, with same specific gravity as the fuels that would be used in the car. Take any vintage Demon, multiply it's rating by 1.076 right off the bat, that's what it dry flows compared to a Holley. If it's a Race Demon, you're getting another 6% discharge coefficient for the scalloped entry, compared to anything with a choke horn still on it, even if the choke plate is removed. The scalloped entry also equalizes the front and rear barrels, as a stock Holley primaries are restricted by the clunky 1950's design choke horn.

what he DID do, was bore out the venturis of the carbs, over what Holley offered, right off the reel. BG "750" had a 1.40" venturi. Holley 750 was 1-3/8" venturis, approx. 1.375"

so...a vintage BG 750 was bored out .025" on all 4 barrels, with the standard 1-11/16" throttle plates. His "750" scalloped entry Race Demon carb, wet flowed, actually flowed around 807cfm dry flowed, that's more than a Holley 800 DP 4780, or 780 3310, which were rated by Holley using DRY FLOW.

The vintage 825 Race Demon, had 1.42" venturis, i.e. bored out another .020" over the 750 Race Demon venturi size- but it used an 850 Holley 1-3/4" throttle baseplate. Yet he only rated it at 825 cfm. Holley puts an 850 baseplate on their 750 main body, and calls it a 950. So who was inflating the numbers here ? Again, add 7.6% to the BG 825 for a dry flow number, it's actually an 888cfm carb, if compared to a Holley. Holley fudged way over that number, to 950 in their advertising, for the same baseplate/venturi combination.

BG used this approach right across the board on all their carbs. I have one of his old Holley reworks with the BG stickers on the bowls, from his pre-Demon era. All 4 barrels are bored out .025" over the stock Holley 750 size, to 1.400" - and the top is completely scalloped like a modern Holley HP. Actually Holley COPIED the BG reworked carbs to make their new HP's. Prior to that, Holley HP carbs just had the choke horn milled level with the air cleaner mounting ring. There was still a remnant of the choke horn protruding on early Holley HP carbs. BG also managed to get from 975-1025 cfm from the Holley 850 1-3/4" baseplate -- 1-9/16" venturi combination (1.562"). There was a Demon 950 with 1-3/4" throttles, 1.500" venturi, and a Demon 1050cfm carb, with 1-3/4" baseplate, and 1.59" venturi. That was a stock Holley 850 venturi opened up .030"

He did it with wider selection of venturi sizes, up/down from what Holley offered, and the superior scalloped air entry, better boosters, and higher discharge coefficient.

BG came right out and said, race motors will produce a depression of 6" water at WOT, and testing at any pressure higher than that is a moot point. Well that's only about .45" HG. However, flow testing at a higher pressure is required, to simulate all conditions the carb will see on the engine.

[GTO-relic]

ps- BG would adjust a carb size downward in cfm, using booster changes.
the 750 Street Demon had 4 downleg boosters
the 725 Road Demon was same dimensions, with straight boosters on secondaries blocking some flow.
their 725 could be shortened to a 625cfm with annular boosters. meaning annulars could cut 100cfm

Holley did some of the same thing, but not to such a degree, on their 750/780/800 family:

750cfm 4779 Holley DP had 4 equal venturis, 1-3/8", with downleg boosters
3310-1 vac. sec. rated 780cfm had 1/16" larger secondary venturis, i.e. 1-3/8" primary, 1-7/16" secondary, with downleg boosters, so it was a slightly "SPREADBORE" design.
4780 rated 800cfm DP also had 1-3/8" & 1-7/16" venturi combination, but the secondary downleg boosters had thinner legs than the 780 vac sec, giving it 20cfm more for 800cfm total.
3310-2 onward revisions of 3310 Holley were rated 750, they had the 1-3/8" & 1-7/16" venturi combo as well, but had straight boosters on all 4 barrels that were larger, blocking some flow, losing 30cfm, so it wasn't a 780 anymore, it became a 750.
this is why the good 3310, always was, and will be, the 3310-1. it's the one with metering blocks on both ends. you can make one by putting the front blocks on both sides. but you'd still have the straight boosters on a 3310-2 and later.

Stealth Carburetors used to sell a Holley rework, it was made on any 3310 core. they would put 2 front 3310 metering blocks on it, front and back, get rid of the rear metering plate, so it was a 4 corner idler adjustable carb, and would polish out the bores approx. .020"-.025" oversize, install (4) annular boosters, drill all 4 throttle plates with idle air bypass holes, mill the choke plate off, and scallop the entry just like an old BG Holley rework. it was sold as an 800cfm vacuum secondary carb. they gained with the scallop and bigger venturis, and lost a little with the annular boosters, and ended up around 800cfm. a carb like that with annular boosters would have electrifying throttle response though.

there's a tendency to just look at the throttle plates, when judging a Holley design...take some time, measure the venturis, and look closely at the boosters.
epiphany will strike.

[Formula jg]

X2!
I love my Mighty Demon.

[GTO-relic]

BG did more with less, because he was custom tailoring carburetors for each specific engine,
whereas Holley was selling many different SIZES of carbs, in 50cfm step stairs increments, DP and vac. sec., and letting the buyer work it out, as to what one worked best on their specific application.
2 different approaches.

I called BG when he was still answering the phone, and building Holley reworks to specific applications, back in the 1990s.
He built us a Holley 850DP, for a 470 CID Pontiac, with E-heads, Victor intake, with 10:1, and a solid roller cam 242/252 Comp
this was back in the 1990's. to this day, that was the best, most responsive street carb I ever bolted onto an engine, period.
it had 4 drilled throttle plates, and the idle mixture only needed to be adjusted 1/8 turn from where he set it at. unbelievable...
He called it the "general competition" carb. Just like the later Race Demons he sold.
he was able to do this, just from the specs on the phone, for cam, CR, CID, vacuum at idle, gearing, weight, intake, headers, trans, tire size, driving style, etc.
the throttle response would rip your head off at any rpm. the owner said "this thing is scary now".
it was 4000 lb. with driver, in a 72 GTO, with 6 speed Nash, and 3.70 gears. Full stock everything. It had a stereo in it, rugs, heater, wipers, lights, and full exhaust. Like a show car. license plate, daily driven. The owner had never even street raced before, he drove it to the track, cut a 1 second (not a typo) reaction time, and it went 12.60 at 110mph granny shifting it, letting off gas completely between gears, and launched it like a school bus going up a hill from a stop.

we had tried a Holley 4781 DP first, it fouled the plugs black, stunk like gas idling, burned your eyes, had some power, but it stalled every time we hit the brakes. You could back up 20mph hit brakes, no problem, it wouldn't stall. but going forward, it would stall instantly. brand new Holley from Summit. we returned it for refund.

The BG carb, has golden brown tan plugs, in daily street driving. Perfect burn.

here's a later BG Demon to Holley comparison:

Holley 4781 DP, 1.75" throttles, 1.560" venturis- 850 cfm dry flow

Race Demon 825- 1.75" throttles, 1.420" venturis- 825 cfm wet flow.
i.e. 890 cfm dry flow.

the vintage Race Demon has 40cfm more flow, with a .140" smaller venturi
that's because of the scalloped entry, better boosters, main body, baseplate. smoother, more precise.

and it has better emulsion. 3 emulsion bleeds per barrel in the metering block, instead of only 2 like an old Holley.
the engine gets a better vaporized mixture.
and...removable/tunable air bleeds, idle feed restrictions since day 1.

BG isn't out of business because he didn't know how to build carbs, he was amongst the best at it.
He's out of business, because the company took loans against all their real estate, assets, to fund operations, like all companies do...and lost their arse during the 2008-2010 real estate/housing/banking crash. That's because a bank loan at 6%, turns out to be 200% interest over principal, with compounded interest.
He was taken out by predatory lenders and banks. Just like everyone else. Gobbled up by the comglomerates.

[Tom Vaught]

Sorry GTO-relic, Bud you know little about Holley carbs. (I worked for Holley Engineering in Warren Michigan at their Engineering Center in the 1970s.)

"whoever posted this, you need to do some research.

BG Demon carbs were wet flowed at 1.5" HG/20.4" water. The corresponding DRY FLOW number would actually be approx. 7.6% more than what BG rated them at, compared to a Holley, because Holley DRY FLOWS their carbs for rating. BG also gained 6% discharge coefficient for the patented scalloped air entry on the Race Demon carbs at that time, compared to a Road Demon/Street Demon with a choke horn on it. the BG owned Demon Carb. company put their test specs in writing, it's on page 44 of the Demon Carburetor manual.


Holley carb flowed on their Wet Stand (Same one used since WWII with Stoddard Solvent every carb designed for production). They also had wet stands at their Water
Valley Production Plant. They tested at 1.5" hg or 20.4" H2O.

Pictures of the Wet Stands are in every Mike Urich Book published.

With 29 posts total you are for sure a phony. Please remove these incorrect posts
Moderators.

Barry Grant worked as a technician for Holley carb at one time I believe at Water Valley.

So your false info is just screwing up my accurate info.

Tom V.

[GTO-relic]

you stated that Barry Grant inflated the CFM numbers. He did not. Actually Holley did, with their 950, that really flowed around 800-830.
so..why didn't that high end flow equipment you used at Holley, pick that up ?

If the Holley test equipment is so ultra-high end, how come they put .037" idle jet orifices in carburetors,
then you have to tell everyone here to change it to a .031" ?? that's 6 sizes off from the factory.

take a 400-428-455 stock Pontiac engine. bolt on a Holley 850 4781 DP carb brand new.
run it for 5 minutes. pull the plugs.
what do you see ?
black as coal tar.
how do your eyes and nose feel while the car idles in the garage ?
I've got 40 years of experience with these myself as well.
They run too rich. They always did. Let's be frank and honest about this.

[Tom Vaught]

Originally Posted by GTO-relic

you stated that Barry Grant inflated the CFM numbers. He did not. Actually Holley did, with their 950, that really flowed around 800-830.

In my timeframe the airflow numbers were as I stated. An 850 cfm carb flowed 830 to 870 cfm at 1.5" HG or 20.4" H2O.
Since you are a young guy you do not remember the history of where Holley was forced into the CFM wars by the other carb people. I totally agree that a
750 cfm double pumper #4779 flows 750 cfm not 950 cfm like tha later advertising stated. Same deal for them #4781 850 cfm carb vsm the advertised BS that said it flowed 1000 cfm.


so..why didn't that high end flow equipment you used at Holley, pick that up ?

It did pick it up you were just not listening.


If the Holley test equipment is so ultra-high end, how come they put .037" idle jet orifices in carburetors, then you have to tell everyone here to change it to a .031" ?? that's 6 sizes off from the factory.

Never said that, that is a lie, and the 850 cfm carbs were .038" IFRs and the
750 carbs were .036" IFRs not .031.

take a 400-428-455 stock Pontiac engine. bolt on a Holley 850 4781 DP carb brand new.
run it for 5 minutes. pull the plugs.
what do you see ?
black as coal tar.
how do your eyes and nose feel while the car idles in the garage ?

First off Holley carb in the 70s when I worked there is not the same company that went bankrupts three times since I left the company. I cannot get blamed for BS that happened to carbs made today.


I've got 40 years of experience with these myself as well.
They run too rich. They always did. Let's be frank and honest about this.

In the 1970s Holley carbs were about 1.5% rich when flowed on their Stoddard Solvent/Air Flow benches. So smart guy do you know why they test with Stoddard Solvent?

40 years, good for you. Now learn to make carb statements based on a year time frame, not generic statements. 1970s carbs, 1980s carbs, really is a simple concept. Same deal with 1st Holley Carb bankruptcy, 2nd one, third one.

You are a smart guy, you just said that, post up real info based on the timeframe. Not after Holley left Warren Michigan and went south.

Tom Vaught

[Tom Vaught]

Apparently the members should do their research before taking as gospel any posts
on the PY Board.

Tom V.

[Tom Vaught]

After I left Holley and went to Ford Engineering, a bunch of my old Holley carb associates would invite me over for lunch and then we golfed in the Holley Golf league.

Will never forget a know-it-all young Holley Employee who was trying to make a 4 corner idle carb out of a two corner idle carb. He failed terribly. Drilled holes right thru the center section into the venturi bores above the throttle blades. So he threw the casting in the trash and took another casting off the shelf and learned from "a old timer" how to do it correctly. I heard he was later fired by Holley after he went south with the rest of the Holley "Aftermarket" Guys. The OEM PRODUCTION guys were later absorbed by Borg Warner when Holley needed money. They wound up with nice stock retirement plans from BW vs loosing their Holley jobs down south.

Marvin Benoit and Marty Brown started Quick Fuel because the people down south did not have a clue with carbs.
Chuck Gulledge started his own carb business. Steve White went to Bosch as a fuel systems engineer.

So happy for you that you like Barry Grant. Barry personally sent me my Holley TRI-POWER Pontiac Intake manifold version 3 after the first two casting needed a lot of work. The history was in the PY Forums somewhere. Barry and I never had any issues.
You seem to have an issue that I know the actual history of Holley carb.

Barry built some nice "later versions" of original Carb companies designs like the Autolite inline carb.
Too bad the set-up was only large enough for a mild SB Chevy engine.

So I will grant that you know something about the LATER history but nothing about the history before WW-II when Holley made 3000 cfm aircraft carbs that were WET-FLOWED. And all of the Engineering Carbs at Warren Michigan were also wet flowed.

Tom V.

[GTO-relic]

it's a well known fact,
the Holley 950HP, only flows around 790cfm
and the Holley 1000HP, only flows around 900cfm
for some reason Holley's awesome flow equipment,
is not capable of putting an accurate flow number on their carburetors,
It was not BG who was inflating numbers, it was Holley all along.
this is a case of blaming BG, for what Holley was actually doing themselves.
it's a blatant case of false advertising. see it below, just one case of the many threads on Holley cfm fudging.

https://www.speed-talk.com/forum/viewtopic.php?t=9463

by highhat » Sun Feb 10, 2008 5:16 pm
I just called Holley this week to get flow numbers. I have a 950HP and wanted to move up to a 1000HP.
I got them to state flow numbers. They said:
950HP flows 790
1000HP flows 900/

Holley 950 carbs
Post by bigjoe1 » Sun Feb 10, 2008 10:34 am
When the 950 Holley cam out. I tested one against a good known 850 I use on the dyno alot. On a 406 Chevy that was at 625 HP , the 950 LOST 23-24 HP over the 850. When I tested the carbs on my flow bench, the 850 flowed about 55 CFM MORE than the 950. The holley 950 is really a 750 main body with an 850 throttle body. Not what everybudy thinks it is.A real 850 will work well for your 434 combo.

[Cliff R]

Another entry into the market:

https://www.enginelabs.com/engine-te...it-carburetor/

Looks like they tried to correct all the issues found with Holley and the Holley clones produced over the years. Take a gander at those billet aluminum metering blocks, already tapped for quick tuning changes, even for the PV.......

[Tom Vaught]

I documented a NASCAR Carb for Ford Racing, back in the 2006 time frame that was similar in design.
They just wanted me to tell them what all of the circuits did. I posted about this in a Carb Thread.

"Eye Candy" for sure. Today is the day of "Write the Check" carb tuning.

I would stick with a Braswell or Bo Laws carb personally if I was told to buy a carb.
But the carb supplier will "hook" some with cash money to burn.

Tom V.

Kind of like the Trucks today with 7 computers on them.
Do a fine job, but a 64 Pontiac can still get me down the road just fine.

Tom V.