#61  
Old 12-05-2017, 06:10 PM
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Thanks for the input, Sprocket.

Tom V.

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  #62  
Old 12-05-2017, 09:29 PM
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I haven't ran a choke for 25 plus years..normally a couple pumps to fire and hold at 2000 rpm or do a throttle tickle for 30/45 seconds..depends on temps..Over winter I'm putting a fast idle solenoid on just to bump idle and hold for warm up...

I always find it curious when people will post "the car fired right up cold and idled down to a smooth idle right away" with non-choke carbs..they are either full of it... or the carb is very rich at idle...

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Old 12-05-2017, 09:39 PM
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When I was a kid, many many years ago I used a Manual Choke and had a cable that attached to the 64 Choke Housing. Everything on the Farm had Manual Chokes so it was not a big deal for me to use one.

All that being said, I will wait for a few more responses before I decide whether to say much about Chokes (manual or otherwise) these days.

Thanks for the post.

Tom V.

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  #64  
Old 12-05-2017, 11:00 PM
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Tom,I have never setup a choke on my Holleys,had a man choke on my 1 bbl 63 tempest,have the factory choke on my tripower.Tom

  #65  
Old 12-05-2017, 11:06 PM
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Thank You Tom.

I personally do not see people driving nice street cars in Michigan Winters. California, Florida, and and Texas are basically year round venues for nice cars.

Factory choke should be fine for your driving.

Keep the responses coming.

Tom V.

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  #66  
Old 12-06-2017, 08:13 AM
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Even though this discussion is about Holley Carburetors I will add on the Minimal Choke Discussion a link I had from my files concerning Rochester 2G and 2GC carburetors as it is well written and agrees with comments I have made in the past about condensation of fuel on the intake runner walls. The info, I am sure, came from Rochester Products Engineers.

http://www.carbkitsource.com/carbs/t...buretion9.html

"PURPOSE

The purpose of the choke system is to provide an extremely rich fuel mixture for cold engine starting and operation. This rich mixture is required because fuel vapor has a tendency to condense into droplets of raw gasoline upon coming into contact with the cold wall of the intake manifold. This action seriously robs the amount of fuel which normally would reach the engine cylinders to be ignited and burned.

You undoubtedly have noticed that if you place a glass of water in a room how moisture will immediately begin to form on the outside of the glass. This is condensation being formed by the warm air coming into contact with the cool surface of the glass causing beads or droplets of water to be condensed from the moisture in the air collecting on the glass. This same process takes place inside a cold engine."

That being said, I have also posted that when you do a quick "Tip-In" fuel is pulled from the walls, mixes with the increased air coming into the intake manifold, and any additional fuel then tries to replace the fuel on the wals of the intake so you get a lean spot (hesitation) in the engine.
The Accelerator Pump adds extra fuel to replace the fuel removed from the walls and still have the mixture be slightly rich.

So some say it does not work that way. All I can say is why do you need 4 Accelerator pumps on a Tunnel Ram intake with a large plenum volume if the situation mentioned above did not apply.

I also verified this process a few years ago on dyno testing (with EFI) and a camera in the intake manifold plenum. Physics did not change, be it a carb system or a EFI System. Fuel still attaches to the plenum walls even on EFI cars. Physics does not change.

So look at the link on Rochester carbs and Choke Function as it is a good bit of info. Different parts (Holley Vs Rochester) but the RP Engineers had it covered.

Tom V.

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  #67  
Old 12-06-2017, 08:31 AM
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From what I recall ( I hope I am right? ) if you have a Carb jetted / running right for safe cruse conditions, like 14.5 to 1 ratio at 60 degree temps, getting that motor started stone cold at that same temp or lower calls for near the exact reverse fuel ratio!

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Old 12-06-2017, 11:12 AM
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I have 6 cars, all with mild engines. I live in Michigan, so I drive my cars whenever the roads are dry and salt free, usually some time in March to as late as early December. I start them from as cold as 25* F.

All have heat operated or electric chokes, but only my slant six Dart has a fully operational heat riser. The rest have missing or blocked heat risers, and my 289 Mustang has a blocked crossover (which was a mistake...it runs ragged when cold).

The Dart starts the best cold; I can usually take off on a cold day almost immediately, even though it misses and spits a bit for a short time. There is almost no hesitation. My Firebird is almost as good; it is only missing a heat riser but still has manifold heat.

My '53 Buick has a wired shut heat riser (it heat soaks otherwise). It requires a lot of careful driving so it doesn't stall when cold, as do my Skylark and Mustang. They all have tip-in sags until they are sufficiently warm. The Corvair will start and run OK cold, but it has a fairly large tip-in sag until it gets hot. I have another set of carbs to try on it; I think there's a quirk in its current carbs, as it has always had a slight tip-in sag at higher speeds.

Wow, that was a long winded answer to a simple question!

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Last edited by Aaron65; 12-06-2017 at 11:27 AM.
  #69  
Old 12-06-2017, 07:02 PM
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Actually Aaron65, for Michigan, All of the engines are telling you that they would like to be a bit richer during the cold/warmup phase of the driving cycle.

Great Info.

Tom V.

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  #70  
Old 12-07-2017, 04:47 PM
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A Bit of History today.
Here is a link to one of the first Vacuum Secondary Carburetors filed by Holley Carburetor

https://www.google.com/patents/US2766024

It was filed Jan 8, 1953 and 3 years later (normal turn-around time) a Patent was issued on Oct 9, 1956.

The reason why I am posting this is two fold.
1) The patent describes almost exactly how a 3310 Vacuum Secondary carb works when the secondary barrels are opened.

2) The second point is this statement:

"In the operation of large ...horsepower automotive engines, two carburetors in parallel are used and the primary carburetor is opened first by the first throttle and the secondary throttle of the secondary carburetor is OPENED LATER by the first throttle. With automatic transmission, a mechanical connection between first and second throttle has proven entirely satisfactory. With the ordinary synchromesh transmission, a mechanical link found to be unsatisfactory."

So there is a reason why Auto Trans Pontiacs like Double Pumper Mechanical Secondary carbs and Manual Transmission Pontiacs do not do as well with Double Pumper Mechanical Secondary carbs. Enjoy.

Tom V.

ps Old Dudes like Tom S are not full of beans.


So the Holley People were aware of the "Drive Issues" with using Mechanical Opened carburetors and syncromesh Manual Transmissions even in 1953.

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Last edited by Tom Vaught; 12-07-2017 at 05:36 PM.
  #71  
Old 12-08-2017, 02:47 PM
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Jet Extensions
Uncovering the secondary jets can cause a stumbling problem, and no amount of accelerator pump tuning will cure it. This occurs when a car leaves the line so hard that the fuel in the secondary bowl is pushed up against the rear wall, uncovering the jets. Quick Fuel, Holley, and others offer Jet Extensions that correct this situation. Whenever Jet Extensions are installed in a carburetor equipped with a Secondary Power Valve, the Power Valve must be removed and the PV hole plugged. Jet size must then be increased accordingly

This is because the Power Valve fuel inlet passage is .250" HIGHER than the Jet Opening in the jet when mounted on the rear metering block.

When you add the Jet Extensions you also need the Notched Black Float installed in the rear bowl.
Jet Extensions have progressed from a small brass tube soldered into a Holley jet (usually about 3/4" long and 3/16" outer tube size to Large Diameter 'Slip on" extensions, to "Holley sold" machined extensions that go into the metering block and then the Holley jet screws into the end of the extension.

The Slip-On Jet Extensions made from a fuel resistant plastic (when new) seemed to seal well but after several jet swaps would sometimes leak air and not pull fuel from the rear of the bowl properly. The metal (usually brass) Slip-On Jet Extensions never did seal well and always leaked air. They basically were 'Feel Good" extensions but did nothing except get your money.
The Holley Machined Extensions seem to work best and last a long time without air leaks. Many people buy a hand full of the things and install them on the most used jets. Then use a wrench to swap them out vs a screwdriver.

Notched Floats

Notched Floats have been around for a long time. They work well with the different Jet Extension parts out there.
Depending on if the "Notched Float" was created by the racer or purchased by the racer can be the difference between a leaking and poor functioning Rear Float vs a properly working float. Some racer modded ones work well based on the sealer used on the float.

So now you have the "Trick of the Week" Jet Extensions and "Notched Float" in your "Race Holley Rear Bowl" and you still have a hesitation when you launch the vehicle on the line.

Many Racers miss the fact that the Power Valve Stem that seals the Power Valve from the Fuel Bowl is .250" higher vs the Jet Opening therefore the Main Wells will see air past that Power Valve when the car accelerates and the fuel rushes to the rear of the fuel bowl. So now your Jet Extensions and Notched Float really did nothing to remove the hesitation in the acceleration curve.

So for Drag Racing with a "Hard Launching" vehicle, the Power Valve circuit needs to be blocked with a Power Valve Plug and the Jetting raised from 6 to 10 jet numbers. Holley actually offers carbs with no Power Valve Drilling in the Rear Metering Block for that reason. Plugs not required, PV gaskets not required (at that Position) and just basic Rear Jet Changes required to tune for max MPH.
So Holley Engineers Did that "delete" Mod for a reason.

Bowl Vent Baffles.

Holley basically offered two styles of Bowl Vent hardware: A Brass Deflector that installed on two bowl gasket pins and a press-in Plastic Vent "Whistle"

The Brass Deflector was for "Non-Raced" street vehicles that were never accelerated hard or braked hard.
The Plastic Vent "Whistle" was for vehicles that could be driven aggressively. Braked harder or accelerated harder.
When the vehicle was "Braked Hard", the Whistle "Inlet" being 3/4 of the way into the back of the fuel bowl kept fuel from banging off the metering block, moving thru the vent tube, and entering the air stream and passing thru the engine as a very rich mixture.
So we solved that problem.

But then you have the RACER who accelerated hard. When the vehicle was "Accelerated Hard", the Whistle "Inlet" being 3/4 of the way into the back of the fuel bowl allowed fuel that banging off the rear of the bowl wall, to pass thru the vent tube, and enter the air stream and pass thru the engine as a very rich mixture, causing a hesitation part way down the track.

So then a Compromise Solution was required.
The Bowl Vent Whistle was trimmed to about 1.5" (from the steel retention pin to the end of the Whistle). (About .400" removed from the whistle and the .250" square opening at the top of the whistle recreated in the new shorter length whistle.

So now fuel banging off the rear wall of the Float Bowl would collapse like a surfing water wave before entering the fuel bowl whistle.

So now you know a bit more about what Racers do certain mods and why Holley added given parts to a carburetor.

Tom V.

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Last edited by Tom Vaught; 12-08-2017 at 02:54 PM.
  #72  
Old 12-09-2017, 07:34 AM
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Tom Vaught
"When I was a kid, many many years ago I used a Manual Choke and had a cable that attached to the 64 Choke Housing. Everything on the Farm had Manual Chokes so it was not a big deal for me to use one."

My experience with a choke is very similar to yours, so using a manual for startup just comes second nature also.

I prefer it to this day, for a few reasons, it omits unwanted components, de-clutters the carb/intake area, and gives me better control.

As I've always required a choke this brings me to the crossover, mine is heated, a wise man once said "physics do not change" better combustion = faster warm up = less wear.

Since I don't modify much, I rely on designers for systems, and engineers to ensure they work properly.

Tom Vaught
"So there is a reason why Auto Trans Pontiacs like Double Pumper Mechanical Secondary carbs and Manual Transmission Pontiacs do not do as well with Double Pumper Mechanical Secondary carbs. Enjoy."

This is very surprising, I have always had a stick car and never used mechanical secondary's, but not because I was privy to this information.

Is this just for street applications or is it because there is a converter in the equation?


Again, Much Thanks!

Frank

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  #73  
Old 12-09-2017, 10:15 AM
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Thank You Frank for your comments on the choke topic.

Looser converters tend to "flash" to a higher rpm. Even though it is only fractions of a second, that "delay" helps with a Double Pumper Carb's sudden Drive Mode Change to supplying WOT fuel and air to the engine. The engine has a chance to find its own acceleration rate to compensate for the sudden additional mixture change going into the engine.

With the Manual Transmission the engine and the driveline are tied together. Now the carb says I am going to make a significant change in air and fuel supplied to the engine. The problem is the driveline is trying to resist that sudden change in rpm of the components. So there is a delay in the engine's ability to digest that extra fuel and air mixture. So you get a MECHANICAL HESITATION in the performance curve. Change one component, add a torque converter and remove the clutch, and you get a whole different response from the engine.

That being said, manufacturers do not want to give up fuel economy so they came up with 'Lock-up" Converters that allow both modes.
Throttle Position Sensor detects an abrupt throttle change, converter "unlocks", rpm in engine goes up just like a old style converter, and performance is there.
After the WOT (or less) rpm change event, the Computer and TPS agree that the engine is in a mode where the "lock up" converter can be used again. If the Trans Engineer and the Engine Engineer did their jobs correctly the change is hardly felt.

That brings to mind another Drive Mode with a Manual Transmission. The time it actually takes to make the shift to the next gear.
Old days is: Acceleration Event, release the Pressure Plate from the Drive Disc, match the gears using the Trans Syncros, move to the new gear, release the clutch, accelerate at the new trans ratio.

NEW State Of the Art Manual Transmissions (and Auto Transmissions have Gears on BOTH sides of the main shaft. So now when you are accelerating in First Gear, the Computer is already setting up the gears for the Trans to be in second gear on the opposite counter-shaft gear set. So the computer releases the 1st set of clutches/gears and applies the second set of clutches/gears and the shift is made in microseconds. And as long as the TPS Sensor says we are still at WOT, it gets the next set of gears/clutches ready to make the shift.
It can do this for all 10 speeds of the transmission. This is a GM/Ford "Team Designed" Transmission in production in the new Corvette and other vehicles.

So again, Engineers can figure out how to get the best of the MANUAL TRANS features and the smoothness of the Auto Trans features.
But they are fixing a Fuel and Air Physics Problem in the engine.

Sorry for the side track as the discussion is on Holley Carburetors, not Modern EFI and TRANS Calibrations.

Tom V.

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Last edited by Tom Vaught; 12-09-2017 at 10:20 AM.
  #74  
Old 12-10-2017, 01:59 AM
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Tom Vaught
"Change one component, add a torque converter and remove the clutch, and you get a whole different response from the engine."

You didn't get sideways, all the info contained is relative and essential to carb type as it may take info on several components to explain fully the effects of selection/calibration/modification.


"they are fixing a Fuel and Air Physics Problem in the engine"

The cause and effect of old vs new puts it into perspective, as mentioned previously a good analogy sheds light for a novice such as myself.

Appreciate the elaboration I suspected as much, but the rest of the story, priceless!


Much Thanks,

Frank

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  #75  
Old 12-10-2017, 11:20 AM
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Going to try today to post some Holley Jet Flow Numbers in Cubic Centimeters per Minute.
Will see if it works.
This is a Test.

Jet #___Orifice Dia. =________Area________Flow (cc/min)
40_______0.040__________0.001257__________117
41_______0.041__________0.00132__________122.5
42_______0.042__________0.001385__________129
43_______0.043__________0.001452__________135.5
44_______0.044__________0.001521__________142
45_______0.045__________0.00159___________149
47_______0.047__________0.001735__________163
48_______0.048__________0.00181__________170.5
49_______0.048__________0.00181___________178
50_______0.049__________0.001886__________186
51_______0.050__________0.001963__________195
52_______0.052__________0.002124__________203
53_______0.052__________0.002124__________212
54_______0.053__________0.002206__________221
55_______0.054__________0.00229___________231
56_______0.055__________0.002376__________241
57_______0.056__________0.002463__________251
58_______0.057__________0.002552__________262
59_______0.058__________0.002642__________273
60_______0.060__________0.002827__________285
61_______0.060__________0.002827__________298
62_______0.061__________0.002922__________311
63_______0.062__________0.003019__________325
64_______0.064__________0.003217__________341
65_______0.065__________0.003318__________357
66_______0.066__________0.003421__________374
67_______0.068__________0.003632__________392
68_______0.069__________0.003739__________411
69_______0.070__________0.003848__________429
70_______0.073__________0.004185__________448
71_______0.076__________0.004536__________470
72_______0.079__________0.004902__________492
73_______0.079__________0.004902__________517
74_______0.081__________0.005153__________542
75_______0.082__________0.005281__________566
76_______0.084__________0.005542__________587
77_______0.086__________0.005809__________615
78_______0.089__________0.006221__________645
79_______0.091__________0.006504__________677
80_______0.093__________0.006793__________703
81_______0.093__________0.006793__________731
82_______0.093__________0.006793__________765
83_______0.094__________0.00694___________795
84_______0.099__________0.007698__________824
85_______0.101__________0.007854__________858
86_______0.101__________0.008012__________890
87_______0.103__________0.008332__________923
88_______0.104__________0.008495__________952
89_______0.104__________0.008495__________987
90_______0.104__________0.008495__________1014
91_______0.105__________0.008659__________1080
92_______0.105__________0.008659__________1150
93_______0.105__________0.008659__________1205
94_______0.108__________0.009161__________1260
95_______0.118__________0.010936__________1320
96_______0.118__________0.010936__________1375
97_______0.125__________0.012272__________1440
98_______0.125__________0.012272__________1500
99_______0.125__________0.012272__________1570
100______0.128__________0.012868__________1640

Well it looks like it worked.

Now that I know it posts the info and it is easy to read I will make a few comments.
Holley jets are manufactured in production volumes and then each jet is run thru a machine and sorted for size.
This gets you a pretty close flow number for your Jetting of the Holley carburetor. Notice I said "Close".

Now there are other jets out there like the Comp Cams Maxi-Jet. These jets tend to run on the HIGH SIDE of the Jet Flow Numbers
so if you are running in a class where the Holley Specs say the carb came with a 72 Primary Jet and a 78 Secondary Jet the Maxi-Jet
will get you a bit more fuel to the engine vs the normal guy running the stock Holley Jets. Might be more money but also might give
you a slight edge on the guy in the other lane.

Today is just passing on a little info that might make a difference in racing. Not for Bracket Guys.

Tom V.

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Last edited by Tom Vaught; 12-10-2017 at 11:46 AM.
  #76  
Old 12-11-2017, 08:26 AM
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Decided today to talk about Holley Carb SAFETY PROCEDURES.

There are lots of stories out there about Carb issues and people losing their car in a fire or people getting hurt badly or even death from a Carb/Fuel System issue.

1) If the carb/engine have set over the winter or a period of more than a couple of weeks, get yourself a fuel resistant squirt bottle or a squirt oil can (paint it RED vs Blue or Silver) and use that (with gasoline) to squirt fuel into the CARB VENTS of the Holley Carburetor. This method will restore the fuel that evaporated from the fuel bowls when the vehicle and carb sat for a period of time. DON'T DO the pour a half of a glass of gas down the venturis of the carb and expect it to run properly. 1) High probability of a Backfire and potential carb fire. 2) The Fuel Bowls WILL still NOT have the correct amount of fuel in them to have a close fuel/air calibration and be able to run properly. Squirt the fuel in the vents, check the fuel level with the carb "Sight Plugs" and at least when you bump the car sideways you see some fuel sloshing out of the opening.

2) NOW go to WOT 2 times on the accelerator and then let it sit for a few seconds and allow the fuel to vaporize in the intake.

3) At this point (if you are working with a helper) you should have a pail of water and a lightly soaked T-Shirt (wring it out so that it is just barely damp to the touch) and a fire extinguisher close by. USE THE T-SHIRT FIRST IF YOU GET A BACKFIRE THRU THE CARB. 99 TIMES OUT OF 100 THE SHIRT WILL WORK VS BLASTING YOUR ENGINE WITH FIRE RETARDENT CHEMICALS. Just throw it over the carb. The fire will go out.

4) The Choke should be set or the driver ready to lightly modulate the throttle to keep the engine running. Once you have the engine running, you are good to go, unless the engine sits for long periods of between fire-ups.

PART 2

If this is an initial fire-up and not a restart after weeks of storage, you still need the Damp T-Shirt and the Fire Extinguisher mentioned above as well as the Timing Light and Tools to adjust the timing and fuel on the engine. You want the timing to be right on the engine before you try to set the carb, not afterwards.

If you have a remote Electric Fuel Pump make sure that it works before you attempt to start the engine. Turn it on and look at a fuel pressure gage to see that you have fuel pressure. If no gage, turn the pump off and open the sight plug and see if the fuel level is right with a slight bump of the fender.

If you have leaks of the fuel system FIX THEM before trying to start the engine.

Speaking of leaks, I have posted this before.

Friend has a car. He can't get it to run.
Diagnoses that the mechanical fuel pump is bad.
Friends tell him install a Electric fuel Pump vs change the PIA to get to Mechanical Pump (Ferd vehicle with "crash loop" around fuel pump).

So he works on the Electric fuel pump installation, it gets dark, he goes to bed, goes to work, and the next afternoon he continues on the fuel pump install. (Doing the wiring of the pump).

So the pump is installed, and he needs power to run the thing apparently. So after the fact, we know he hooked up a hot wire from the battery to the area where the pump was installed. Wire was on the ground burned. Close to the wire was a in-ground drain set-up to wash a car outside. Fire inspectors say the drain had fuel in it because it burned the bottom of the car, my friend over 90% of his body and set the house on fire by migrating to the basement drains.
Basically a barbeque deal with my friend involved.

So what happened. The fuel line was "Jerry Rigged" for the fuel pump install and leaked into the car wash drain. My friend touched the hot wire to the pump and a spark occurred. Drain became a barbeque with my friend as the meat.
He died from that deal.

So the fuel system issues cannot be ignored or "Jerry Rigged".

That is all I have for today. Like they used to say on the old Cop show: "Let's Be Safe out there"

Tom V.

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Last edited by Tom Vaught; 12-11-2017 at 08:33 AM.
  #77  
Old 12-11-2017, 07:39 PM
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Anyone recognize this Holley carb?
It has an interesting feature.
It was designed in the early 60s.

More on it and Booster Tech tomorrow.

Tom V.
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  #78  
Old 12-11-2017, 08:33 PM
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oldblueponcho oldblueponcho is offline
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Quote:
Originally Posted by Tom Vaught View Post
Anyone recognize this Holley carb?
It has an interesting feature.
It was designed in the early 60s.

More on it and Booster Tech tomorrow.

Tom V.
I do believe I aw a couple back in the seventies. I forget exactly what on though.

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  #79  
Old 12-12-2017, 09:19 AM
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Tom Vaught Tom Vaught is offline
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The carb in the previousl post was a 625 cfm 2 barrel carb #6425 Holley that used a Annular Discharge Venturi (not a Annular Discharge Booster)


After you read the article, this is what we will know:

a) "There is no such thing as a carb that is too big"
I can agree with that as when I worked for Holley, we tested 350 cid "Pro Stock" type engines with two Special Dominators that flowed 2400 cfm each or 4800 cfm total for the engine. 10,000 plus rpm engine and ONE BARREL feeding ONE Cylinder. The Booster Signal on that one barrel was Extremely High. It would go to sleep for 7 cylinder firings and then go to Max Signal for that specific cylinder event.

b) "Fuel Vaporization and Droplet Size does make a difference"

c) "Booster Gain" is an important Air/Fuel Tool for "Maximum Horsepower"

d) "Booster Gain" is an important Air/Fuel Tool for "Maximum Horsepower" But there is physics involved in doing it right
"Low Gain Boosters" can at times perform better vs "High Gain Boosters", so generic rules typically do not apply and can actually generate less performance. Temperature makes a difference

e) Small changes in a booster design can improve or make worse performance in an engine. "Copy Cat" Mods typically done without knowledge of the physics and good evaluation tools: Flow Benches and Dynos, as well as track testing will make a difference, most times for less performance. Beware of "Trick of the Week" Carb Modifiers.

Here is the Article:

http://www.hotrod.com/articles/0511p...boosters-tech/
Written by David Vizard on October 4, 2005
Quotes By David Vizard:

Understanding Boosters Can Enhance Top-End Output Without Impairing Bottom End.

Tom V.

ps I really like the way David V presents info in an article.

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  #80  
Old 12-12-2017, 01:27 PM
TedRamAirII TedRamAirII is online now
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I usually thought that there was a "carb too big" when the engine flowed, for example 700 CFM and the carb flowed 950 cfm?

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