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#41
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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. |
#42
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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. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#43
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Same ole Tom
You can't even agree with someone that's agreeing with you |
#44
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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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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#45
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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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466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2 373 gears 3200 Continental Convertor best et 10.679/127.5/1.533 60ft 308 gears best et 10.76/125.64/1.5471 |
#46
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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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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#47
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Quote:
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.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#48
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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. |
#49
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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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#50
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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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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#51
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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. |
#52
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Before WHEN? Before you took off the Q-Jet? Before the last time you filled up with gas? Before lunch?
RUNNING rich, or SMELLING rich at the tailpipe. Huge difference. HOW do you know it was running rich? O2 sensor results? Help coil? Huh? Quote:
Regardless, a carburetor is not going to cause an oil leak at the exhaust manifold. Quote:
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? |
#53
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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???? __________________ . . |
#54
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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
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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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