[PAUL K]

Originally Posted by Formulas

The old school Holley 4bbl is rated @ 1.5? pressure drop take the same base plate with a smaller venturi flow it at a higher drop 2.0 and the carb will pass the same CFM.?

These numbers do not represent an actuall equasion use only for a trend model

Agree..... That's why I said true CFM which I believe were close to Holley's original ratings. That would make a 4779 close to 750, the HP950 was around 820 and the redesigned Edelbrock could flow 850 using the same test standard.

[GTO-relic]

Originally Posted by PAUL K

I can believe a 1.39 venturi could flow a true 850 CFM.

the true cfm would be on a wet flow bench to simulate the fuel being in suspension. and that is very hard to find today, cuz it costs millions to build a bench like that. sure it may flow 850, at an unrealistic pressure drop an engine never sees, and dry.

an 850 Holley is rated at 1.5" Hg (Mercury) by Holley, that would be 20.4" of water on a Superflow 1000. Buy a new Edelbrock 1308 for $957, drop it on an SF1000, open all 4 barrels, see what it flows dry. Cuz then someone is lying.
Is it Holley who's been building 850's since 1960's, or Edelbrock who just started making them last year, changed owners, and choked down the venturis from 1.56" to 1.39", then added 4 annular discharge boosters, which block even more flow. That VRS carb probably doesn't even flow 700 cfm, let alone 850.

When BG would put straight annular boosters on their 1.56" throat 1025cfm carbs, the carb would drop to 820cfm rating compared to the original downleg boosters.
When they did the same to their 1050cfm 1.59" throat carb, it would drop to a 950cfm rating. This was wet flowed on a very, very expensive flow bench. $250,000 back in the 1990's.
That was with the correct 1.56" throat, and an even bigger 1.59" throat, and standard 1.75" butterflies.
Now imagine what it would flow with a 1.39" throat. No way in hell will it be the same. BG never put annular nozzles on a 750 or lower carb for this reason, it chokes the flow. All the BG Demon 1.40" throat carbs with downleg boosters flow 750-775cfm.
That's about what that Edelbrock 850 would flow, IF it had downleg boosters.
It may only flow 650cfm with the straight annulars, and 1.39" throat.

[PAUL K]

Originally Posted by GTO-relic

Cuz then someone is lying.

BG never put annular nozzles on a 750 or lower carb for this reason, it chokes the flow.

Ummm...... BG offered several 750 CFM carburetors with annular booster and rated them at 750 CFM.

[GTO-relic]

the smoke and mirrors cfm game was exposed decades ago.
this has all been documented, hashed out 20-25 years ago.
the buying public is smarter now, which is why that Edelbrock VRS will flop.
no one on this site has even replied that they bought one yet,
what's that say ?
here's why:

[GTO-relic]

dry flow is what exaggerates cfm numbers on a carburetor.
but even if someone did flow the VRS 850,
at 1.5" HG/20.4" H2O standard,
it's going to flow a lot less than a Holley 850.
Holley got all that BG plant/equipment flow gear,
from the BG Demon bankrupcy buyout,
back around 2010-2012.

[GTO-relic]

If Edelbrock makes a "950" carb,
which they said is in the works,
that will be in the ballpark for a big block 455-500 engine.
because then it will finally have a throat size,
similar to compete with the old Holley 850 style BP family of carbs,
everyone has been running for 55+ years.
If they abandon the annular boosters,
and make some downleg booster carbs, with larger venturi.
then they have something, to build on in the future.
we can't even get the emulsion/air bleeds from them,
for the carb. what good is it then ?
and we have to rely on Holley jets, power valves for the VRS as well.
it seems like a half hearted market test by Edelbrock on the surface.

[GTO-relic]

ok...using that high end, big dollar flow equipment,
we know these sizes venturis, butterflies wet flow these numbers,
and this was WITH a fully sculpted top inlet, no choke horn.
the Race Demon patented sculpted inlet, everyone now copies, uses,
look at the difference in flow drop, when annular boosters are used,
no other changes- the flow drops 100-200cfm for same butterfly/throat size
ALL the Edelbrock VRS carbs have annular boosters, and smaller throats.
look at the flow charts from 25 years ago:

[GTO-relic]

btw, BG never made a 750 Race Demon with a normal 1.375" throat.
they were all hopped up to 1.4", 1.42"
he did that for a reason. they were somewhat flow limited.
he had been porting/polishing the 4779 since 1980's,
and sculpting the inlet.
when time came to make one from scratch,
he opened up the throats a bit, right in the casting from the get go.

[PAUL K]

Not sure how you can tell by a picture how much a carburetor flows. I can assure you with first hand experience a 1.39 venturi could flow similar to what a basic unmodified 4781would flow. The Edelbrock carburetor's offer a lot of nice upgrades. Hopefully the Internet BS'ers don't kill it.

Edelbrock ingeniously increased the flow of the basic Q-jet design and most folks (including some "experts") look right past the obvious modifications that gained the flow and say it was just an advertising gimmick..... Chit has changed a lot since Holley sold their first 4781.

[GTO-relic]

now, are we supposed to believe, a 1.39" throat, with annular boosters, without a sculpted inlet, can flow 850 cfm ?
they obviously don't because everyone is already complaining, losing 2 tenths, 2 mph, losing 150HP on the dyno, still down 16HP after tuning, going rich at 4000rpm even with the power valve hole plugged, and returning the carbs.
they can visually SEE the venturi is a lot smaller, then have trouble tuning it.
they don't even need a flow bench. their cars are slowing down, and the dyno numbers are falling drastically.

[PAUL K]

Originally Posted by GTO-relic

btw, BG never made a 750 Race Demon with a normal 1.375" throat.
they were all hopped up to 1.4", 1.42"
he did that for a reason. they were somewhat flow limited.
he had been porting/polishing the 4779 since 1980's,
and sculpting the inlet.
when time came to make one from scratch,
he opened up the throats a bit, right in the casting from the get go.

You're original post said BG never offered a 1.4 venturi 750 with annular boosters.... That is misinformation, they did.

One can't debate or learn from a person that changes mis-facts as he goes along.

Let's changed the subject and you can fill us in on your 1,000 horsepower 4X head project.... How is that progressing?

[GTO-relic]

one of these with 1.75" throttles (Holley 850 size), and 1.42" throats, downleg boosters, sculpted inlet, flows 825 cfm.

put annular boosters on it, they're bigger, block airflow. it would probably flow 725 cfm, or less.
that's what the VRS has, on even smaller 1.39" throats.
the inlet on the VRS is not sculpted. 850 cfm from a VRS 850 is an advertising gimmick.

in reality, the 825 isn't even big enough, for a 450-500" engine- it can use a 975cfm carb no problem.

http://52.55.101.62/archives/2001/09/project460/

[GTO-relic]

All the old BG Demon carb ratings were established by wet flow testing, with all 4 barrels wide open, at 1.5" Hg./20.4" h2o.
When fluid is introduced into an airflow rig, the test pressure will increase 2" h2o per Joe Mondello- who also used a wet flow rig to flow heads. Reher/Morrison obtained a Mondello CFM-WFB2000 freestanding wetflow bench from Mondello. They pulled 28" h20 at 1" valve lift on one of their R&D Pro Stock heads- and stated they gained vast amounts of knowledge in very short time using the Mondello flow rig.
What this means is, if the flow bench is on stable at 28", and the fluid is turned on, the flow pressure climbs to 30". Then it has to be turned back down to maintain 28" with wet flow on. The same phenom would occur when BG was flowing his carbs.
If you then took those BG carbs, or Mondello heads, and flowed them dry, they'd flow a higher number than when they were flowed wet.
an 825 Demon could flow around 865 cfm on a dry bench at 20.4"
if it was put on a 28" bench, it could flow around 965 cfm.
BG flowed the carbs complete all 4 barrels open with that huge flow bench,
so the effect of the inlet bowl scalloping could be measured accurately.
other carb companies were flowing only one barrel, then multiplying by 4 to get a number. or flowing the front half of a 4bbl, and multiplying by 2.
that doesn't take into account the choke horn, or removal of it, scalloping, etc.
if the Edelbrock VRS line of carbs is being flowed dry at 20.4", or at 28", that would explain the ratings they are being given.

[GTO-relic]

https://www.enginebuildermag.com/200...-flow-testing/

Mondello, Morgan
old news but very informative

https://www.youtube.com/watch?v=t9La8gR_k80

https://www.motortrend.com/how-to/su...-flow-testing/