[Tom Vaught]

If nothing else you should know now quite a bit more about the different parts and circuits of a Holley carb and how they function.

There are still some good Holley People out there. David Braswell does a nice job.
David's father was a Pontiac Dragster Racer in the old days and for his time frame was very fast.

Tom V.

You have most of the basics now so the next step will be talking about how to get the extra fuel to the manifold by using multiple PVCR
passages, reducing the air bleeds on the high speed circuits, and adding boost referenced Power Valve Drillings to the carb.

[Tom Vaught]

I mentioned reducing the air bleeds on the carb.
I have several Boosted Engine Carbs I have collected over the years.

An example of some of the mods for higher boost applications would be:

1) Larger Needles and Seats and more Needles and Seats: (2 N&S assemblies per Fuel Bowl).

2) Replacing the typical .031" Primary High Speed Air Bleeds and .028" Secondary High Speed Air Bleeds with drilled .015" High Speed Air Bleeds.

3) Plugging and epoxying (fuel resistant) the emulsion holes in the metering blocks completely shut.

4) Installing 12 hole Annular Discharge Boosters

5) Drilling into the carb center cavity from the Air Cleaner Boss hole and then installing a Pitot Tube in the airstream to pressuring the two Power Valve Cavities (after you drilled a Connecting thru passage that will activate both Power Valves at the same time.

Modifying Power Valves for Boost Reference operation.

Modifying the secondary metering block for a lower Fuel Bowl feed and Boost Spring Retention.

Notched Black Floats and Rear Jet Extensions

Modded 2.5" or 3.5" 4 window Power Valves for a lighter spring and Boost Mode.

And there are more "Secret Mods" that the carb builders will not tell you on threat of death.

Most Every Boosted Carb guy can built you a nice Boosted Carb. Just some can build you a carb that is a level higher vs the rest.
Luhn Performance made 863 HP at 13 psi with a very basic 455 engine at 5300 rpm and over 900 lbs/ft of torque at 4800 rpm.

We are talking 1500 HP capable 850 cfm Double Pumper Carbs here, not a basic 863 HP simple mods carb. (with Intercooling and Turbos). Dominators can easily go over 2000 Hp and have in many dyno tests. Just look at Steve Morris site at all of the videos where he has proved that deal.

Tom V.

[Tom Vaught]

Typically if you had a .015" High Speed Air Bleed in the 4 positions (Primary and Secondary), you would have the same .015" High Speed Air Bleed in the 4 positions (Primary and Secondary) on a E-85 Carb.

If you had #92 Main Jets in all 4 Corners of the carb with Gas you would also have #92 Main Jets in all 4 positions (Primary and Secondary) on a E-85 Carb.

Now the Idle Air Bleeds are typically .070" on a 850 Holley Gas Carb and they might be in the mid 50s range on a E-85 Carb.

And with a High HP E-85 Carb the shooters could very well be in the .040"+ range to get the Accelerator Pump right.

With a E-85 Carb or a higher Boost Gas Carb you will need at least 4 Power Valve Channel Restrictions.

That being said, in 90 times out of 100 with a C&S carb you will be very close right out of the box on a typical Pontiac Engine with Boost. Dyno Testing is really the best way to dial in a carb for the Power side of it.

Tom V.

[Tom Vaught]

The Holley Carb experiences excessive heat with a "Blow Thru" Holley Carb boosted system and no inter-cooler
every time you decide to light them up on the street. Inlet Charge Temps could be 350+ degrees F.
So later we will discuss how to lower that Inlet Charge Temperature to the Holley Carb in a few ways.

Inter-cooling is one way. We will discuss why 120 degrees Inlet Charge Temp vs 350 degrees Inlet Charge Temp makes using a Inter-cooler one of the better ideas for Boosting.



Tom V.

[Tom Vaught]

I have several projects going on today so not going to WASTE TIME typing info when GOOD info is already out there from people like Turbosmart on Inter-cooling.

http://www.turbosmart.com/technical-...rcooler-works/

Read the article and I will add more info later.

Tom V.

[Tom Vaught]

Time for a bit of Airflow Math.

Lets calculate the pounds of air flowing into an 455 Pontiac Engine for two different Boosted Vehicles.
(one that is NOT Inter-cooled and the other one is Inter-cooled).

For both cars we will use a Volumetric Efficiency of 0.85 and will limit the engine rpm to 5500 rpm.

Volume, in cu.ft per minute = (5500 rpm x 455 cubic inches) / (1728 x 2) = Engine CFM.

(5500 x 455) divided by (1728 x 2 ) = 2502500 / 3456= 724.1 cfm.

This holds true for both cars, both intercooled and non-intercooled will be moving 724.1 cfm of air into the cylinders at 5500 rpm.

As we will see however, the "MASS OF AIR FLOW" flowing into the engine will not be the same.

We will also assume that the Discharge Air Temp is about 250 degrees (actual will be 258 degrees F which we will see below).

How we got an actual temp of 258 degrees F:

Temp into engine= 70 deg F + 460 = 530 deg R

Pressure into engine= -0.5 psig + 14.7 = 14.2 psia. The -0.5 psig is the Air Inlet Restriction from the Air Filter and Inlet Pipe Losses.

Pressure out (or the Boosting Device Pressure) = 19 psig + 14.7 = 33.7 psia. psia is pressure in square inches absolute.

Pressure out / Pressure in = 33.7/14.2 = 2.373 (this is the compression ratio). Also called the "Pressure Ratio" of the Boosted Air going into the engine.

Temperature out = 530 + 530 x (-1+2.3730.263 ) = 717.8 deg R - 460 = 257.8 deg F.

That is how hot the air would be with the 19 psi of boost pressure and no inter-cooler. That Holley Carb WOULD BE HOT.

Later I will calculate the Non-Inter-cooled Air vs the Inter-cooled Air and give you the Horsepower Difference (assuming we can lower the Inter-cooled air temp to 130 degrees F.

Tom V.

[Tom Vaught]

Ok, so now we will figure out the Air Mass (which makes the HP when fuel is added properly)
for the Non Inter-cooled engine and the Inter-cooled engine.

Non Inter-cooled engine first.

Suppose the car an '71 GTO, and it is not intercooled. The temperature in the intake manifold is 257 degrees F.

The car is running 19 psi boost. What is the mass of air the engine is using?

Absolute temperature = 257 deg F + 460 = 717 deg R.

Absolute pressure = 19 psig + 14.7 = 33.7 psia

n (lbs/min)= 33.7 psia x 724.1 cfm x 29 divided by 10.73 x 710 deg R = 92.89 lbs of air per minute (ideal).

lbs air per minute actual = lbs/min ideal x vol. eff. =92.89 x 0.85 = 78.956 lbs air/minute

Now the Inter-cooler car.

The car is running 17 psi boost. What is the mass of air the engine is using?

Absolute temperature = 130 deg F + 460 = 590 deg R.

Absolute pressure = 17 psig + 14.7 = 33.7 psia

n (lbs/min)= 33.7 psia x 724.1 cfm x 29 divided by 10.73 x 590 deg R = 111.8 lbs of air per minute (ideal).

lbs air per minute actual = lbs/min ideal x vol. eff. =111.8 x 0.85 = 95.01 lbs air/minute

95.01 lbs air/minute (Inter-cooled) minus 78.956 lbs air/minute (non Inter-cooled) = 16.06 lbs air/minute improvement.

One lb of air mass will typically make 10 horsepower so 10 HP x 16.06 lbs air/minute improvement = 160 additional horsepower that the vehicle sees due to inter-cooling the air charge.

So your Boosted Holley Carb will be a lot cooler, will make a lot more HP and you will still be using the same sized carb.

Tom V.

[Tom Vaught]

Talk for a couple of minutes about inter-cooling systems (mentioned earlier). Basically two types:
Air to Air Systems and Water to Air Systems.

Air to Air Systems use a "radiator" type unit (with much larger air flow tubes) and it packages in front of the normal Radiator.
Most are made out of aluminum pieces.
Hook up is easy: Boost device, inter-cooler, bonnet, carb, engine.

Water to air systems have more pieces:
You have the Air Side of the water to air inter-cooler and you have the water side of the water to air inter-cooler. The air side plumbing is just like the air to air stuff: Boost device, inter-cooler, bonnet, carb, engine.

The water side is Water Reservoir, Water Pusher Pump, Inter-cooler, then back to the reservoir.
See Pics attached.

Water to air is better for racing as there is more thermal mass and it takes longer for the boosted air to heat cold (40 degree ground water) or ICE WATER vs an air to air system (where the ambient air might be 85 degrees outside) and you are already at a 45 degree temp disadvantage compared to the Water to Air system before you make the run.

Cool air to the carb makes the carb air density much better vs hot air flowing thru the Holley carb.

Tom V.

[Tom Vaught]

There's no denying that supercharging and turbocharging engines is becoming more and more popular every day. Substantial increases in horsepower and torque, along with stock-like driveability make these power adders very appealing to a great many enthusiasts. In order to take these power gains to the next level, an intercooler must be employed, and we're going to tell you why you might need one, and what is available

The term intercooler actually dates back to the beginning of air-charge-cooling technology when piston-driven aircraft used multiple superchargers to boost power output. Air-charge coolers were installed between these superchargers (hence the inter part of the name) to reduce the air-charge temperature. Technically speaking, most of the current air-charge-cooling designs should be called aftercoolers since they chill the charge after the compressor, but the market has been slow to adopt the more accurate description.

At this point, the term intercooler is used much like Kleenex or Coke, in that they have come to represent the type of product rather than a brand or exact product. For the duration of this article, we'll refer to intercoolers and aftercoolers simply as charge coolers.

It helps in the discussion of air charge cooling, or the concept of cooling the air that enters the engine, that superchargers and turbochargers both pressurize the intake manifold side of the engine. When you add more air and fuel, the result is typically increased power and torque. Compressing the air, does have a negative though which is heating the air charge going into the engine. Heated enough, the hot air can cause detonation, among other engine issues.

To offset the increase in air charge temperature, a charge air cooler (intercooler/aftercooler) is employed. By forcing the compressed, and subsequently heated, air intake charge through an intercooler, the temperature is reduced, as is the air pressure caused by inter-cooler restriction. When both of these events occur, the result is a cooler and more dense air charge.

The increased density air charge, when combined with the a proper amount of additional fuel, produces higher horsepower and torque. The cool, dense charge also allows for more ignition timing to be run, which also adds to the increased power output.

The first inter-cooler to be discussed is the air-to-air charge cooler.

In this design, Ambient air is passed through a cooler core, which is typiocally placed at the front of the car in the direct path of oncoming air. The air passes over the fins of the core, which pulls the heat from the air charge within the core.

The air-to-liquid charge cooler transfers the intake charge heat to typically water or water and ice. That water or water and ice liquid is then passed through a second heat exchanger that is air cooled and finally sent back to a reservoir. The system constantly repeats this process. Such systems have been used in Turbocharged Buicks and Supercharged Ford applications, starting in the 1980s.

Air-to-Water Systems can be very efficient. The system is more difficult to add to an existing vehicle, but if you design a new vehicle package it is easy with a V-engine-because the inter-cooler core can fit in the valley sometimes. Pontiacs have a deep valley. With the right design a inter-cooler "brick" in the valley might work well.

This is assuming a EFI system, not a Blow-thru Holley Carb system.

Air-to-water charge coolers are usually heavier than air-to-air systems because of the additional components that make up the system-fluid, circulation pump, radiator, and plumbing. Though they may be heavier in weight, air-to-liquid charge coolers generally feature lower overall pipe and intercooler length, which can reduce turbo lag.

Plumbing coolant hoses may be fine for street/strip applications and is far easier than running large-diameter air tubes, but many today put the self-contained inter-cooler assembly in the right passenger seat area on a race car as you can package a water reservoir/heat exchanger at one location and run short hoses to a water tank in the rear of the vehicle.

One final point in this post, as well as supplying the engine with more air to make more power, the internal engine temperatures drop at the same timel, which allows for a more advanced (aggressive) Ignition-timing map using todays ignition systems.

So all of the parts have to work together, The Holley Carburetor (or EFI), the Inter-cooler, the Ignition System, the Fuel System, and the basic Boosted Engine Pontiac design.

Tom V.

The Vortech "Mondo" Inter-cooler (last picture) worked well but took up a lot of space under the hood and was a pain if engine disassembly was required. Most of the inter-cooler parts (in the other pics) could be adapted to a Blow-thru carb system for additional power.

[charlie66]

Hi Tom.

So the air to water also needs a radiator for the water. I never knew this. It would be nice if someone could post a picture of this set up in the car...

Thanks for the information Tom...

[Tom Vaught]

Here you go Charlie. You can see the Premium Heat-Exchanger and the water lines to it.
The Heat Exchanger removes heat after a quick burst of power on the freeway.
It would not be able to keep up with your Multiple Banzai launches/runs as it takes about 3 minutes
of driving to remove the heat in the water reservoir (from the previous blast down the road).

Tom V.

[charlie66]

So you're saying water to water is not for me?

That im better off with air to air ?

Thank you for the pic...

[Tom Vaught]

For what you are doing, on the street, YES.

If you were racing for money and not making multiple passes (30 min/1 hr between runs) THEN a ice water tank and the water to air would give you a bit more lead on the other guy at the end of the each race. But you would have already won.

But I think you probably do best out of three "pulls" and the performance would vary too much with the water to air deal (1st run to 3rd run) vs the air to air consistent performance. Understand?

I have some patents for using Air Conditioning to try to cool the water faster between runs but even with that you had to drive over a mile at 60 mph 60 seconds) before the intercooler water temp was close to the first run performance. I was trying to get the performance on each long LeMans straight away (3 straight runs) where the cars run 230+ mph) consistent by recharging the inter-coolers chiller tanks while the vehicle was in the corners and lower speed portions of the race track.

Tom V.

[charlie66]

Understood.. Thank You...

[Tom Vaught]

Today will talk about Very High HP Blow Thru Carb parts (just a little bit).

Many years ago, the IHRA Pro Stock Guys needed more fuel for their BIG engines.

So a couple of racers worked with a company called PCI and came up with Dual Needle & Seat Fuel Bowls so now they had twice the fuel flow capability going into the bowl vs the typical Holley carb fuel bowl.

Because they also had a double float in the bowls they needed a larger bowl and more room for the same actual fuel inside the bowls. But the PCI Bowls worked well for their time period.

Then a outfit called McClintock Fuel Bowls came out with massive fuel bowls that were also supposed to have a fuel anti-foaming design. Not sure if the design ever worked but I have a set of those bowls somewhere.

A number of years later a Blow-thru Carb outfit decided to make new fuel bowls for Blow Thru Carbs (using their own design). PCI and McClintock were basically no longer making fuel bowls. Their design worked pretty well and fed 2000 HP+ engines on Steve Morris Dyno.
Look at first 3 pics below. Company is called Superior Airflow Technologies. Extreme Velocity Fuel Bowls they call them

Later still C&S Carbs made their Dual Inlet Fuel Bowl, BLP Carbs made a Fuel Bowl, Quick Fuel Carbs made a fuel bowl (now owned by Holley).
So the bowls can be bought again IF you have the need for them.

At PRI one year they had a Carb Bowl outfit selling Bottom Feed Needles and Seats. These were to reduce foaming inside the bowls.
They have a nice video on this issue on the web https://www.youtube.com/watch?v=3aVEwud70I4

A different video from another source.
https://www.youtube.com/watch?v=s-q1eJu1Wz8

So have fun learning about "simple" fuel bowl design stuff today. Reality is they are not simple at all.
Holley Engineers did stuff for a reason.

Tom V.

ps These people make a EXPENSIVE DEAL Bowl.
https://apdracingstore.com/products/...foam-fuel-bowl

[Tom Vaught]

So far we have discussed several subjects as related to the Holley Carburetor.
The Bonnet that fits over the Carb Air horn, the Pressure Box that can fit the Holley carb inside,
and and the Draw thru System where the Carb has a regular Air Cleaner installed on the airhorn.

If you have a Blow Thru Boosted System the Holley carb is down stream of the Boosting Device, be it a Centrifugal Supercharger or a Turbocharger.

If you suddenly slam the throttle shut, say at the end of the MPH Lights, the Boosting Device is still spinning close to max rpm (be it a Turbo or Centrifugal compressor.

When you do this the Compressed Air in the ducting from the boosting device to the carb bonnet has no where to go. This pressure spike is very hard on the Boosting Device. If it is a belt driven deal then the belt tries to remove itself from the drive pulleys. If it is a Turbo the Turbo goes into massive surge and tries to bend the compressor blades into undesirable shapes. $$$

So we need to somehow remove the potential for pressure spikes in the plumbing.

For mind boosting systems Bosch made a "compressor By-Pass Valve that would bleed off the pressure in the system using a 1" Hose plumbing system. See Pic #1.
It was ok for very mild systems but lacked the ability to remove a bunch of air quickly and protect the Holley carb and the boosting device.

So I have included a couple of diagrams of how the parts fit and work in two modes: Open Mode and Cruise Mode.

In Cruise mode the air from the turbo (for example) follows a normal path thru the turbo and then goes to the open throttle plate on the carb.

In the open mode the Throttle plate is closed and now the by-pass valve is open and lets the air that can't go thru the engine any longer do a race track pass thru the compressor by-pass valve, thru the turbo and the back to the compressor by-pass valve to begin the "loop circuit" again.

A Blow-Off Valve would just dump the air into the engine compartment instead of recirculating it thru the Turbo.

So you have a picture of a "baby" Bosch CBV and pic #4 is a Race MONDO CBV with a much much larger valve. But the real high HP engines actually need two of the Mondo Valves many times. They are Basically Blow-Off Valves.

So the idea is Protect the carb and the boosting device by using a tool that relieves pressure on quick throttle closure events.

Tom V.

I will try to post the other images tomorrow.

[Tom Vaught]

Today I will try to add a couple of Extra Images to the discussion. The First Image is the Vortech "Mondo" Compressor By-Pass Valve.
Rarely though is it used in By-pass Mode, most times it is plumbed to just dump air into the engine bay when the throttle is closed.

Years ago, a PY Member, had a Trans Am with the home built Procharger Belt Driven Supercharger installed on the engine.
He had a By-pass valve installed but decided that it would be cool to route the discharged air thru a couple of hoses to the
Fender Extractor Vents location on his Trans Am.

He would come to Norwalk, get the car to the line, stage the car, blast off the line and some distance off the line his wife would be waiting to pick up the supercharger belt that would be laying on the track.

Part of this issue was the Brackets were a early design from a guy named Bruno in New Jersey and were not really that good at
not allowing the Supercharger to move. If the supercharger moves, the belt comes off.

The second part of the issue was the Hose on the Bypass Valve could not dump the excess air fast enough so the Supercharger
still had a SURGE ISSUE. Car was fast if he never had to pedal it. Pedal it and the belt came off.
The cause was the Compressor By-pass Valve Plumbing (extra hose routing).

A Second Cause was the way the by-pass valve was installed in the piping. It needed to be on the outside curve of the plumbing so that if the end of the curve was blocked (Throttle shut) the air took the "Off-ramp" vs having to do a 90 degree "Stop Sign" turn.

I have added the Turbonetics Godzilla By-pass Valve (center) and a schematic of a closed throttle flow schematic thru the CBV.
The point being, high rpm "Closed Throttle" Pressure spikes will cause parts to fail. Holley carb blades to bend, hoses to be blown off,
turbos to have bearing thrust issues and fail, Belts to be laying on the street. You really need to pay attention to the plumbing.

Wreckmaster mentioned in a post on the board about adding a third CBV to his plumbing (after the inter-cooler) to relieve the pressure spike from the throttle blade being closed and the inter-cooler being between his other CBV valves. Inter-cooler was basically blocking the back flow from the throttle and the potential for failure of the piece was high. He is running EFI vs a Holley Carb but the issue was the same.

Tom V.

[CraigG.]

Probably already said - PLEASE DUPLICATE THREAD ON RACE SECTION - if possible.
Thanks, Craig

[Tom Vaught]

The thread will be a sticky Craig.
That has already been decided by Bart.

Just putting the sticky info together right now.

Tom V.

[Tom Vaught]

TOOK THE DAY OFF, WILL TRY TO POST UP SOME NEW INFO TOMORROW.

Tom V.