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Old 06-24-2020, 03:05 PM
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The point being they still cause a flow loss, whether it's big or small is getting away from the main point of the post, to further point out what you guys were saying in the first place about CFM ratings.

The fact that the throttle bores are more than a 1/4" larger than a 950HP and only rated at 870 cfm sure makes you think twice.

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Old 06-24-2020, 04:36 PM
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Make it more clear for you, Formulajones.

Until Barry Grant and others used a different test pressure point, in their advertising claims, to dupe the average carb buyer into thinking their larger rated carb was "better" Holley, Carter, Weber, Rochester, Autolight, and others used the agreed upon Carb Test Point of 20.4" of water in their flow stand testing. Even before World War II.

CFM Ratings mean nothing if you do not use the 20.4" of water test point.

That is MY point. If you use a test point other that 20.4" of water then you get INCORRECT numbers. And do not say the larger carbs today require the higher test pressure number as in World War II Holley was building carbs (AND TESTING THEM) that flowed over 3000 cfm per carburetor at 20.4" on aircraft engines. I do not see anyone selling 3000+ cfm carbs in the aftermarket tested at 20.4" of water.

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Old 06-24-2020, 06:36 PM
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Same ole Tom

You can't even agree with someone that's agreeing with you

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Old 06-24-2020, 08:25 PM
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But I can, just I use examples to support your position (and mine).

Yes, I am old. Tell me something I do not already know, Formulajones.

Tom V.

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Old 06-25-2020, 01:28 PM
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So the classic 80496 950hp is 770cfm? Tom in your opinion why is this carb out of the box with minor tweaks so responsive and crisp compared to a 4779 or a 4780. Is it the 850 baseplate in combination with the metering blocks..who ever designed it at Holley knew what they were doing.

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Old 06-25-2020, 03:27 PM
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Davinici in Texas started making the "950"s back in the 80s.

Buddy gave me the main body and metering blocks of the Street 950(850) when he swapped a annular main body on and had stripped out bowl screws chasing AFR so much. Also the metering blocks as he had really drilled out the IFR. They have IFR at the bottom.

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  #47  
Old 06-25-2020, 07:21 PM
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Quote:
Originally Posted by ta man View Post
So the classic 80496 950hp is 770cfm? Tom in your opinion why is this carb out of the box with minor tweaks so responsive and crisp compared to a 4779 or a 4780. Is it the 850 baseplate in combination with the metering blocks..who ever designed it at Holley knew what they were doing.
Good Question!

Let's see why this carb 80496 is better vs the old #4779 or #4780 carbs.

1) Every classic 80496 Holley carb is wet flow tested on a Wet Flow Stand whereas the #4779 and #4780 carbs were spot checked occasionally and compared to a "Master Carb" on Holley's Wet Flow Stand.

2) The 80496 carb has far more adjustment ability out of the box vs the other two carbs.

3) The carbs are specifically designed for Racing applications:
Bigger Cams, Better Heads, Better Exhaust Systems, Higher Compression Ratios, and they have a nice chart telling you where the carb will be most happy vs Engine dosplacement and Engine RPM.

That pretty much covers it all. My 770 cfm number is based on 20.4 " of water test pressure. Would be interesting to know what the actual Flow Stand Test Pressure is when Holley flows each carb.

Tom V.
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Old 06-25-2020, 09:41 PM
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Quote:
Originally Posted by Tom Vaught View Post
My 770 cfm number is based on 20.4 " of water test pressure.
I had to find an on-line calculator/converter to verify what I suspected:

20.4 inches of water is the same as the good ol' 1.5" of mercury vacuum spec that I'm used to seeing.

2-bbl carbs were tested at 3" of mercury vacuum, 4-bbl carbs at 1.5" of mercury vacuum.

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Old 06-27-2020, 01:46 PM
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I looked mine up list 80497 has 1.375 primary venturi and 1.75 secondary. What cfm is it really ?

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Old 06-27-2020, 02:20 PM
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fairly easy to get close with the following calculation.
a 750 Holley carb be it double pumper or Vacuum Secondary has a 1.375" Primary Venturi and Secondary Ventuir
so 750 cfm

The secondary venturi is also the same size 1.375" as the Primary so 750 true cfm.

The Throttle Blades are 1.750" (That .060" larger throttle blade vs the old 1-11/16" throttle blade barely
increases the cfm. )

so your post is incorrect in that you misread the specs.

https://www.holley.com/products/fuel...arts/0-80496-1

Barrels 4
Booster Down Leg
Brand Holley
CFM 950
Choke None
Circuit 2
Condition New
Emission Code 3
Finish Gold Dichromate
Fuel Gasoline
Fuel Inlet Dual
Marine Use No
Material Zinc
Model 4150
Primary Main Jet 79
Primary Power Valve 6.5
Primary Pump Nozzle Size 31
Product Type 4150 Model Carburetor
Secondaries Mechanical
Secondary Main Jet 79
Secondary Power Valve 6.5
Secondary Pump Nozzle Size 31
Supercharged Application No
Throttle Bore 1.750 inch
Venturii Size 1.376 inch

Tom V.

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  #51  
Old 07-12-2020, 07:04 PM
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Default Update- Help

Car was running fine and starting right up before, just running rich:
Removed the carb, carb sprayed and flushed out all orifices, bleeds etc, replaced idle screw cork seals and gaskets, and of course had to help coil the float bowl main body thread.

the only way it starts now is by giving a ton of fuel while its cranking, when it starts its all over the place, tons of smoke out the tailpipes and oil is leaking oil from exhaust manifold gasket, yes from exhaust manifold gasket, not valve cover.

Removed plugs and they were black and caught fire with a lighter. Replaced plugs and still have to give it a ton of fuel while cranking, when it starts, its all over the place and blows smoke and oil leaks between cylinder 3 and 5 exhaust manifold gasket.

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Old 07-12-2020, 07:36 PM
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Quote:
Originally Posted by X72GPX View Post
Car was running fine and starting right up before,
Before WHEN? Before you took off the Q-Jet? Before the last time you filled up with gas? Before lunch?

Quote:
Originally Posted by X72GPX View Post
just running rich:
RUNNING rich, or SMELLING rich at the tailpipe. Huge difference. HOW do you know it was running rich? O2 sensor results?



Quote:
Originally Posted by X72GPX View Post
had to help coil the float bowl main body thread.
Help coil?

Quote:
Originally Posted by X72GPX View Post
when it starts its all over the place,
Huh?

Quote:
Originally Posted by X72GPX View Post
Tons of smoke out the tailpipes and oil is leaking oil from exhaust manifold gasket, yes from exhaust manifold gasket, not valve cover.
I asked in a previous post if the black on the plugs could be oil. Never got a response.

Regardless, a carburetor is not going to cause an oil leak at the exhaust manifold.

Quote:
Originally Posted by X72GPX View Post
Removed plugs and they were black and caught fire with a lighter. Replaced plugs and still have to give it a ton of fuel while cranking, when it starts, its all over the place and blows smoke and oil leaks between cylinder 3 and 5 exhaust manifold gasket.
Again, what do you mean by "all over the place"?

Did you ever adjust the idle mixture screws for best idle?

WHAT is your starting procedure?

Do you have a PROPERLY FUNCTIONING automatic choke? Do you have a manual choke? Do you know how to use it? No choke at all?

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Old 07-12-2020, 08:45 PM
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Car was running fine and starting right up before,
Before WHEN? Before you took off the Q-Jet? Before the last time you filled up with gas? Before lunch?

Before I removed carb - car was running and starting up fine- it may have been before lunch, not sure.

Quote:
Originally Posted by X72GPX View Post
just running rich:
RUNNING rich, or SMELLING rich at the tailpipe. Huge difference. HOW do you know it was running rich? O2 sensor results?

Strong duel odor, no sensors


Quote:
Originally Posted by X72GPX View Post
had to help coil the float bowl main body thread.
Help coil?
HELI COIL


Quote:
Originally Posted by X72GPX View Post
when it starts its all over the place,
Huh?


Quote:
Originally Posted by X72GPX View Post
Tons of smoke out the tailpipes and oil is leaking oil from exhaust manifold gasket, yes from exhaust manifold gasket, not valve cover.
I asked in a previous post if the black on the plugs could be oil. Never got a response.

Regardless, a carburetor is not going to cause an oil leak at the exhaust manifold.

Quote:
Originally Posted by X72GPX View Post
Removed plugs and they were black and caught fire with a lighter. Replaced plugs and still have to give it a ton of fuel while cranking, when it starts, its all over the place and blows smoke and oil leaks between cylinder 3 and 5 exhaust manifold gasket.
Again, what do you mean by "all over the place"?
Running like ****, missing

Did you ever adjust the idle mixture screws for best idle?
Before removing the carb I did

WHAT is your starting procedure?
turn on ignition swith for MSD ignition, turn on switch for fuel pump, pump pedal 7 times and would fire right up

Do you have a PROPERLY FUNCTIONING automatic choke? Do you have a manual choke? Do you know how to use it? No choke at all?
No choke

How the hell is oil leaking out of the exhaust manifold gasket????

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Old 07-12-2020, 09:02 PM
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Failed accelerator pump, or no fuel in the float bowls. 7 full pumps should flood the engine. The fact that it's not is telling me there's no--or very little--fuel actually being squirted.

Next time you attempt to fire the engine, pop the hood, remove the air cleaner lid, work the throttle lever by hand--pump it your seven times, and LOOK at the accelerator pumpshot. Weak? Non-existant? One or two good squirts, then nothing? Something else?

Next time you get it running, adjust the idle mix again.

When you reinstalled the carb, did you use a proper gasket? It had a Q-jet before--is there a vacuum leak at the carb base because the squarebore carb doesn't fit the spreadbore manifold?

"I" would verify that all cylinders run. I still think the bigger problem is the misfire, not the starting issues. Maybe they're related...maybe I'm wrong. Cranking compression pressure on all eight? Cap, rotor, plug wires, plugs?

  #55  
Old 09-19-2021, 06:15 PM
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Does anyone have a tuner in NJ that has a clue on Holley carbs? This has been and continues to be a waste of time.....

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