cooler denser air

[grumpyvette]

Im always rather amazed at the guys that don,t stop and think about the total process of making power and the failure of so many guys to think thru how each step can be improved.
it really doesn,t matter if you have a single carb, dual quads or efi, cooler denser air will result in a more efficient engine , simply because cooler denser air contains more oxygen per cubic foot of air entering the engine, thus allowing more fuel to be burnt resulting in more power potentially produced, and isolating the engine air temp entering the engine your mixing with fuel, from the under hood temps goes a long way to help efficiency
for about every 10 degrees C of increase or decrease in air temps, entering an engines carb, the horse power changes about 1% (hotter is less efficient, as cooler air is denser and contains more oxygen)
IF your not familiar with temps in C celsius that equates too about..
FOR EVERY 15 degrees change in F temp, the horse power changes about 1%
(hotter is less efficient, as cooler air is denser and contains more oxygen)

http://www.celsius.co.uk/converter/

think about that..under hood temps can easily be 100F-120F higher than outside air temps, thats a potential 7-8% decrease in effective horse power over cool air induction
yes it will in most cases take some time, fabrication skills , the ability to measure and think things thru, but the results from some individual creativity and custom fabrication can be amazing, and easily worth extra horse power, with some careful measuring and thought a cool ram air custom fabricated filter air filter housing and isolated air ducting from outside cool air could be designed and built for for most cars
like almost every other potential change you might make theres ways to duct cool outside airflow into the engine compartment to the carb or efi to limit the engine heat it absorbs in transit, cooler air is denser air and it contains a higher volume of oxygen, and its oxygen thats used to release the potential power in fuel, now you can get creative and add a super charger, turbo or add oxygen by using NITROUS, but all those routes will cost you money you might not be able to easily afford, but there are rather simple things you can do to route cooler outside air into your engine rather than allow the engine to suck up higher temp thinner and potentially far less usable air from under your hood.
you can start by getting a good air temp. gauge and measuring the air temps under your cars hood and then measuring the outside air temps. and don,t be surprised at a 80F-120F temp difference after your cars been running for awhile, between the two areas that can potentially be used as a source of air to mix with your fuel.
you might want to get creative and design a custom built hood scoop, vents or air ducts to route cooler outside air into your muscle car or corvettes engine!
http://www.vararam.com/sc1.html
now heres a series of pictures a guy took when he designed a cold air routing duct and hood scoop to route cool air into his carb, from a scoop on the hood, he tested the results and had an 80F-120F difference in intake air temps due to the custom air ducting and insulation layer under the corvette hood, an 80F-100F temp difference will produce an easily measurable gain in power

READ THIS THREAD ALSO
viewtopic.php?f=35&t=5051&p=14478&hilit=clear+filter#p14478

http://garage.grumpysperformance.co...ferant-c-4-hoods-and-hoodscoops.353/#post-434

http://www.parts123.com/corvettecentral/dyndetail.pta?catalog=0000050f&ukey=22025

cool outside air duct entrance

card board separation duct test baffle pattern

rough the surface to get good adhesion on air duct floor surface

thin fiberglass air chamber duct lower surface wall

self adjusting foam baffle seal to isolate incoming air to air filter on carb.

high efficiency ,low flow restriction air filter to prevent crud entering carb

carefully measuring where heat insulation foam baffle contacts duct floor then cutting matching air feed duct to carb

painting baffle or duct surface to match cars hood

insulating reflective surface film added to duct lower floor surface to reflect engine heat from incoming air to maintain max temp difference of air entering engine

https://www.autoaccessoriesgarage.com/Air-Filters/Top-10-Best-Car-Engine-Air-Filters

while its NOT 100% directly related, the resistance to air flow rates , is always a compromise between the air filter's efficiency at removing micro sized particles in the air that cause engine wear and restricting air flow that the engine requires to make power easily , increasing the surface area, number of pleats in the filter medium surface and height all tend to reduce air flow resistance, as the increased surface area reduces the resistance to flow

YOU CAN DO SIMILAR MODS TO A C4 CORVETTE, OR MOST CARS, IF YOU THINK IT THRU!

you can get creative and run duct work or use a custom hood design

read the links
http://garage.grumpysperformance.co...at-manifold-air-temp-sensor.10349/#post-42530

http://garage.grumpysperformance.co...elay-switch-locations-and-info.728/#post-9217

http://garage.grumpysperformance.co...om-air-cleaner-to-fit-your-cars-engine.16490/

http://www.ramairbox.com/

sells kits with the required components,
but with some basic fabrication skills and some ingenuity you would be amazed at what can be fabricated, from parts you can locate locally or from home depot or lowes hard ware, big box stores ,that will work remarkably well at ducting cool fresh airflow into the engine , look over the pictures in this thread, measure your hood clearance accurately, and let your imagination run a bit

BTW it generally helps too place some clay on your current air cleaner and shut the hood to compress the clay to get a better idea as to true hood to carb clearances, and a trip through several local salvage yards , and looking at other cars and trucks and remote mounted air filters and duct work.
may also give you some options

https://www.amazon.com/Claytoon-Set...d=1466872286&sr=8-17&keywords=plastilina+clay

http://www.utrechtart.com/Plastalin...currency=USD&gclid=CN3G75zOw80CFQgaaQodKbgFjA

as always the more tools you have, the more options you look over, and the better your fabrication skills are the more options you,ll realistically have
owning a decent quality MIG or TIG welder and a drill press , and pop rivet guns, certainly helps and mocking up options with duct tape and card board helps give you more ideas

https://utahbiodieselsupply.com/customwork.php
commercial restaurant and beer brewing supply stores can be a gold mine for custom air filter fabrication components if you have a welder and some metal working skills and some imagination

be aware that, the fuel octane, being used, alone is not the only factor here!
iron heads hold heat and transfer heat to coolant at a lower rate!
running a 180f -190f t-stat and use of a 7-8 quart oil pan, an oil cooler will tend too lower the effective operating temp.
both the coolant and oil temps, and ignition advance curve, will effect the range where detonation will occur,richer fuel/air mixtures (12.5:1-13.5:1) tend to burn a bit cooler than lean mix ratios,(13.5:1-15.5:1)
aluminum heads, transfer heat much faster, and benefit from, some, simple mods , like keeping the quench in the .040-.042 range, polishing the piston deck surface and combustion chamber and rounding the edges on the combustion chamber and piston valve notches, will reduce the tendency to get into detonation

always keep in mind what the goal is here, its to keep the lowest temp fuel, and air possible, entering in the carb venturies and cool fuel bowls and lines that deliver the fuel too the carb, thus you want too limit potential heat absorption rates, , a phenolic spacer under the carb base limits heat from the intake manifold coming up through the base of the carb,

a fuel pressure regulator , with a return like bye-pass , that will have a significant volume of the fuel arriving fresh from the fuel tank at the correct pressure and having a significant percentage of the heat absorbed being routed back to the tank, through the return line limits the fuel line pressure and temperature at the carb inlet port.

if your still having vapor lock issues your fuel pump is either not supplying enough pressure and volume to cause a constant return flow or the regulator is not set correctly ,or the carb spacer is not blocking heat flow into the carb.


btw, it also helps to feed the carb with cooler ducted outside air , vs heated air from the engine compartment, as this helps avoid vapor lock and detonation issues

http://garage.grumpysperformance.com/index.php?thr...
THERE ARE A DOZEN WAYS TO ACCOMPLISH SIMILAR AIR ROUTING

http://www.ramairbox.com/

http://www.mjbperformance.com/

viewtopic.php?f=55&t=4113&p=29319#p29319

http://www.hotrod.com/articles/carburetor-dyno-testing-flowing-results/

http://members.shaw.ca/k2pilot/Homeade% ... ticle.html

http://garage.grumpysperformance.co...ferant-c-4-hoods-and-hoodscoops.353/#post-434

http://www.ramairbox.com/

http://www.parts123.com/corvettecentral/dyndetail.pta?catalog=0000050f&ukey=22025

http://www.autospeed.com/cms/A_1023/art ... larArticle

http://www.musclecarfilms.com/Pontiac_Ram_Air_3.html

http://www.knfilters.com/racing/custom.htm

viewtopic.php?f=35&t=353&p=5243&hilit=fiberglass+hood#p5243

http://www.vararam.com/sc1.html

viewtopic.php?f=32&t=3954&p=17008&hilit=hood+vents#p17008

 

[Grumpy]

http://www.elcaminostore.com/assets/pdf/elcamino/70-72COWLHOOD TECH.pdf

http://garage.grumpysperformance.com/index.php?threads/header-paints-and-coatings.6086/#post-57067

the t-stat controls COOLANT temps,
which are generally 15F-25F lower than peak oil temps,
obviously the coolant temps vary as the t-stat opens allowing flow ,
and closes as temps drop off.
your oil temp may read only 10F hotter than the coolant temps,
but its a fact that oil temps vary a great deal during the trip from sump,
oil pump, valve train,and bearings and back to the oil pan sump.
get out a high quality infrared temp gun, and scan the valve springs after 10 minutes of engine run time,
youll notice the oil temp on the rockers is significantly cooler than that flowing over the valve springs
this is the most consistently accurate I.R temp gun I've used for testing

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN
Wide temperature range from -58 to 1832°F (-50 to 1000°C)
any time that your dealing with a potential temperature issue or a trouble issue where
, knowing the exact temperature vs what a gauge might say,
\it helps to have a handy and accurate infrared temp gun handy,
to locate and confirm heat, levels.

 

[Grumpy]

years ago I purchased two of these assortment packs when they cost about 1/2 the current price , Ive tried hard to keep 4 jets in each size in inventory as I use those, 72 jets in assorted sizes for $52 is still a good deal , and it gets better if you buy the pack or two of them, when summit posts a discount code
http://www.summitracing.com/parts/hly-36-181

IF you can read spark plugs , USE A TIMING LIGHT, and use an INFRARED TEMP GUN AND VACUUM GAUGE
http://www.harborfreight.com/cpi/ctaf/d ... mber=93547
A MULTI METER AND TIMING LIGHT WILL BE USEFUL

http://www.harborfreight.com/5-in-1-dig ... 98674.html

http://www.summitracing.com/parts/MSD-8991/

TUNING A HOLLEY IS DAMN SIMPLE

infrared thermometers are a very useful tool to track down issues with tuning, or mal functioning sensors

infrared thermometers are a very useful tool to track down issues with tuning, or mal functioning sensors , without verified facts your guessing.
this is the most consistently accurate I.R temp gun I've used for testing[/img]

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN
Wide temperature range from -58 to 1832°F (-50 to 1000°C)
any time that your dealing with a potential temperature issue or a trouble issue where , knowing the exact temperature vs what a gauge might say, it helps to have a handy and accurate infrared temp gun handy to locate and confirm heat, levels.
viewtopic.php?f=50&t=138&p=168&hilit=infrared#p168

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html

http://garage.grumpysperformance.co...at-manifold-air-temp-sensor.10349/#post-42530

http://garage.grumpysperformance.co...elay-switch-locations-and-info.728/#post-9217


Given constant pressure (which seems accurate), the temperature of the air is inversely proportional to the number of air molecules
So colder air means more molecules, and more air molecules means more energy released in each combustion cycle.
A drop from 30 C to 0 C is roughly a 10% drop measured in Kelvin,
which suggests 10% more energy for each combustion cycle --> 10% more horsepower!

https://wahiduddin.net/calc/calc_hp_dp.htm

http://www.celsius.co.uk/converter/

http://www.carsdirect.com/car-maint...-air-intake-system-improve-engine-performance

http://www.onlineconversion.com/

http://wahiduddin.net/calc/calc_hp_dp.htm

http://wahiduddin.net/calc/calc_da.htm

http://wahiduddin.net/calc/density_altitude.htm

http://garage.grumpysperformance.co...e-required-octane-for-compression-ratio.2718/


for air temperature, colder air entering the engines induction is generally better.
simply because cold air is more dense, so if you put cold air into a cylinder, you could fit more molecules of oxygen in a given volume of air flow,
than if you allow the engine to breath in hot air.
that's a good reason why when people design an air induction system for a performance application,in their muscle cars,
they put in cold air intakes, because they allow access too cooler and denser outside air from a cooler area,
then the engine and exhaust pre-heated air under the hood ,
a standard engine air cleaner assembly breaths around the engine compartment where the engine sits.

theres always a point where more is not better, and colder air entering the engine must be above the dew point where water turns to ice, in the air,
combustion is more efficient at higher temps,

THERMAL BARRIER DESIGNED TO REDUCE HEAT TRANSFER< AND INCREASE POWER

for the combustion temperature of the actual engine,combustion chamber,
efficiency is enhanced through higher compression and increased burn temps and combustion speeds,the higher the compression ratio the faster the burn speeds thus the less wasted energy compressing a rapidly expanding mass of burning fuel/air mix BEFORE the piston and rod assembly pass TDC and the greater percentage of the burn energy that can be actually used to increase engine torque driving the piston down the bore on the power stroke AFTER TDC

thus a good ignition system and thermal reflective coatings on the piston uper surfaces and combustion chamber surfaces that reduce heat loss too the engine cooling system and ceramic coatings on the headers that tend to reduce heat loss help the engine make power. warmer combustion, with cooler denser air containing more oxygen is better for performance. if your car's cooling system is cooling too much, your engine won't run as efficiently, so if your car is running too cold, its best to get it set up to operate within a fairly narrow temperature band.
engine coolant temps in the 160F-200F range with oil temps running in the 180F-215F range have proven to be about ideal in a muscle car.

and yes increased altitude tends to reduce engine performance meassurably
,simply because, a car operating at a higher altitude, performs worse because the air is less dense, and contains less oxygen in the air being compressed so less fuel can be burnt. so less air useful oxygen molecules entering the cylinder.
a carefully designed exhaust header with the correct dimensions, with a ceramic coating to reduce heat energy losses, pistons, and combustion chamber surfaces, with thermal barrier coating and matching cam timing on a high compression engine can be significantly more efficient with some carefully thought through engineering that enhances its thermal effiency and cylinder scavenging, while most people don,t realize the benefits the addition of carefully thought through and well matched components each STACK or MULTIPLY the effect of the matched changes making each more effective than they would otherwise be!

these threads may also help`
RELATED INFO YOU REALLY SHOULD READ!
http://garage.grumpysperformance.com/index.php?threads/lca-or-lsa.11523/#post-53149

http://garage.grumpysperformance.com/index.php?threads/infrared-temp-guns.11444/#post-52521

http://garage.grumpysperformance.co...octane-for-compression-ratio.2718/#post-35581

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/

http://garage.grumpysperformance.com/index.php?threads/four-key-properties-of-fuel.11030/#post-48864

http://garage.grumpysperformance.com/index.php?threads/thermal-coatings.2610/#post-12861

http://garage.grumpysperformance.com/index.php?threads/which-oil-what-viscosity.1334/

http://www.ramairbox.com/

http://www.wallaceracing.com/calcafhp.php

http://hpwizard.com/engine-horsepower-calculator.html

http://www.hotrod.com/articles/airflow-research-cylinder-power/

http://www.powerperformancenews.com/tech-articles/cylinder-head-tech-airflow-vs-power/

http://www.calculator.net/engine-horsepower-calculator.html

http://www.calculatoredge.com/new/horsepower.htm

 

[philly]

this was always my beef with 302 poewred mustng guys... they all drop a 160 thermostat in the car to make it run richer when they are losing power to the lack of thermal efficiency of a cool motor... getting cool dense air in there and running a stock thermostat makes more power... if you want to trick the computer to throw more fuel make a resistor pack for the coolant temp sensor and keep the stock t-stat...

also of note fat too often i see metal pipes used on cold air intake systems... its been that way so long i think maybe im crazy.. but i would rather have one made out of a composite material that wont heat soak like metals will. if they dont offer a plastic style pipe for my application im gonna rig one up...

 

[Grumpy]

routing cooler air that contains a higher concentration of oxygen to the engine may not sound like a modification that is worth the effort to do, after all,what can you reasonably expect to gain?
YES READING THE LINKS IS WORTH THE TIME
http://garage.grumpysperformance.com/index.php?threads/dynamic-vs-static-compression.727/

http://bankspower.com/techarticles/show/22-Cool-Air-Equals-Power

https://www.quora.com/Can-the-hot-temperature-inlet-air-to-engine-can-provide-a-better-efficiency
there are chances of pre-ignition and knocking, if temperature of the inlet air is higher than normal. As the temperature of the air will be higher, the temperature of air-fuel charge will also be higher (petrol engine) which means there are chances of ignition of air-fuel mixture even before the piston reaches its precise point during normal combustion.

The above picture gives a general idea about how knocking occurs.

Generally, during summer season due to higher atmospheric temperatures the air inlet temperature going into the engine will be higher that is why we see a lot of engines shutting off in the middle of the roads.

Turbocharger or a supercharger are few ingenious devices which not only increase the volumetric efficiency (ratio of the amount of air entering into the cylinder to the actual volume of the cylinder) which improves the combustion efficiency but also cools down the inlet air using an intercooler. There are others advantages as well. Now, by using a turbocharger the power output of the engine will certainly improve, but there will be subtle improvements in the overall efficiency of the engine.

http://www.sciencedirect.com/science/article/pii/S2215098615001445

illustrates the effect of oxygen enrichment on the in-cylinder pressure. A maximum of 2 to 4 percent increase in peak cylinder pressures is achieved in 23 to 27 percent oxygen enriched air than ambient air at part load conditions. These indicate a feasibility of increasing the net engine power by reasonable level. There is formation of local stoichiometric mixtures rather than rich premixed mixtures, which leads to rising in cylinder temperature and pressure.

The brake thermal efficiency, which is the ratio between the measured brake power to the product of the fuel flow rate and its calorific value, were calculated and plotted against different loads as shown in Fig. 3. From an ideal perspective, the brake thermal efficiency is affected by compression ratio and the thermodynamic properties of the working mixture. Compression ratio is fixed in this study; thermodynamic properties of the mixture however changed due to the addition of oxygen. An increase in oxygen concentration increases the mixture ratio of specific heats, which in essence increases the potential to convert the mixtures thermal energy to work energy. There is about 4 to 8 percent increase in brake thermal efficiency throughout all levels of oxygen enrichment.

The increase in exhaust gas temperature with increased load and oxygen concentration as shown in Fig. 4 was due to increase in reaction rate, flame velocity and increased heat release rate as compared to heat loss rate [15]. The exhaust gas temperature for all oxygen concentrations were increased considerably.

The brake specific fuel consumption is the ratio of rate of fuel consumption to brake power produced, an important parameter that reflects how good the engine performance is. For a fixed hydrogen to carbon molar ratio (H/C), the stoichiometric air–fuel ratio decreases when the oxygen concentration in air increases. This means that less air is required for complete combustion of diesel fuel. When air mass flow is constant, as in these experiments, the additional oxygen was used to burn diesel and improves combustion. There is about 5 to 12 percent decrease in specific fuel consumption with increase in oxygen concentration from 21 to 27 percent as illustrated in Fig. 5.

Six principle mechanisms that are believed to be responsible for hydrocarbon emissions are crevices, oil layers, deposits, liquid fuel, flame quench and exhaust valve leakage. When liquid fuel did not find sufficient oxygen to burn prior to the end of combustion, hydrocarbon is formed in the exhaust. Since oxygen enrichment ensures additional oxygen inside the combustion chamber more complete combustion is possible and it lowers the hydrocarbon level in the exhaust. Oxygen enrichment can decrease the quenching distance of the mixture [21] as it was found to be a decreasing function of flame temperature. It is well known that the flame temperature increases in the case of oxygen enrichment [7] and this allows the flame to propagate much closer to the cylinder wall and reduce HC emissions. The hydrocarbon emissions were reduced to a minimum of 10% at 23% oxygen to a maximum of 40% at 27% oxygen enrichment levels as seen in Fig. 6.

CO formation mechanism is well established and it is mainly due to unavailability of enough oxygen for complete oxidation. CO concentration is reduced to 15% at full load to 55% at no load and 27% oxygen enrichment as seen in Fig. 7. The extra oxygen atom which is present in the mixture plays an important role in reducing the CO values. Combustion efficiency, although not reported in this article is assumed to be higher for oxygen enhanced combustion [1] and [2] than ambient air combustion and this was considered to play a role in reducing HC and CO emission as well as increasing thermal efficiency.

NO is the major component of NOx in diesel engines and it is the reaction product of nitrogen at high temperature and oxygen enrichment simultaneously. Two major NO formation mechanisms are thermal NO and Prompt NO. However prompt NO is prevalent only in fuel rich systems and it is not a major source of NO for diesel engines. Only thermal NO based on Zeldovich's mechanism is predominant and it is shown as; O + N2 ↔ NO + N, N + O2 ↔ NO + O, N + OH ↔ NO + H. Higher post-flame temperatures and oxygen concentrations during the combustion process results in high thermal NO formation rates [6]. When the oxygen level is increased to 27% the NOx level increases by three times the ambient air as it is shown in Fig. 8. This is the major drawback of oxygen enriched combustion; however, this can be controlled and kept within the reasonable limit by adjusting the fuel injection timing, after treatment techniques

One of the promising results from oxygen enrichment is the significant decrease in smoke density in the exhaust. Agglomeration of soot particle in the diesel exhaust is the major source of smoke in diesel engine. It is formed mainly due to incomplete combustion of fuel hydrocarbons and some is contributed by lubricating oil. Soot formation is strongly dependent on the stoichiometry, temperature, pressure and mixing [18]. Soot in the exhaust gas is dominated by soot formation as well as oxidation. One of the main effects of oxygen enrichment is to increase oxygen–fuel ratio, which in turn improves the oxidation of fuel and suppress the soot formation. Oxygen enrichment also reduces the ignition delay, meaning higher burning rate and shorter combustion duration [15] which further reduces soot formation. The minimum reduction of smoke opacity in oxygen enrichment is 15% at full load with 27% oxygen enrichment, while the maximum reduction is 60% at no load 27% oxygen enrichment. Consistently there is reduction of smoke opacity levels at all loads and oxygen concentration levels as reported in Fig. 9.

 

[Grumpy]

https://www.hotrod.com/articles/1974-plymouth-duster-super-stock-hood-how-to-install/
click the linked info

Is It Worth Getting A Hood Scoop?
Johnny HunkinsAuthor
Aug 27, 2020
To the uninitiated, an air scoop on the hood of a muscle car may seem like a senseless, tasteless add-on, or even a now-useless relic of a bygone era. To others it's perceived as a lifeline to much-needed air for a powerful V-8 engine. For sure, there are some powerful cars out there that through pure engineering genius have no hood scoops at all, and there are cars with scoops that mystify us as to their purpose, although most of those are purely for looks.

You may be trying to satisfy your own mind, win a bet with a buddy, or are researching the topic for adding one to your own car, but to Christian Arriero—owner of the 1974 Plymouth Duster in this feature and technician at the HOT ROD Tech Center—the answer was already clear: he had his heart set on adding a Mopar Hemi Super Stock hood scoop as a companion to the 455hp Magnum small-block under his hood, and that's what we're going to show you in a bit, but first some background.

What Does A Hood Scoop Do?
The primary purpose of a hood scoop is to provide a restriction-free source of ambient air to the engine, which typically sits below the scoop. Since most passenger cars don't have hood scoops, it begs the question, why do some cars have them and others don't? That answer lies in the fact that horsepower is a direct function of the amount of air and fuel that enters an engine. Since the power output of most engines does not require going to the extra effort or cost of adding an air scoop, they are omitted from the OE design. That said, there is often a benefit to adding one, especially if the power output of the engine has been increased over stock.


Interestingly, some cars that might benefit marginally from a hood scoop don't have them. This can be due to manufacturing cost constraints, added complexity of getting the car's inlet tract federally certified, and the potential for a negative effect on aerodynamics—all of which were frequent issues in malaise-era cars of the 1970s and 1980s. One thing is for sure: many of the most potent cars ever offered from the factory came with hood scoops because it made the difference between winning and losing.

SPONSORED CONTENT
Tune in to watch August 24 – 28
By an engine needs roughly 1.6 cubic feet per minute (cfm) for each hp produced. Any less than that will produce a restriction that will limit power to less than the engine's full potential. This is one of the reasons the 2018 Dodge Demon has a large scoop resembling the original Hemi Super Stock hood in addition to air-catcher inlets on the grille and another air inlet hidden in the driver's side fender. With Chris's engine already dyno tested at 455 hp with no restriction above the carburetor inlet, we can establish that his need is around 728 cfm—well in excess of the car's original slant-six's 232cfm requirement.

Related Story: Dodge Magnum 360ci Small-Block Build and Dyno Test


While a larger underhood air cleaner base and lid can certainly supply close to that need, the other part of the equation is the ambient temperature of the air in the engine compartment, which can soar to well over 200 degrees in some instances. Moreover, the engine sheds significantly more heat as power increases. This has an extremely negative effect on both air density (the amount of oxygen actually entering the engine) and detonation (a power killer, not to mention an engine killer). So while a hood scoop may not strictly be required to supply the needed amount of airflow, it certainly aids in power production by virtue of supplying cooler air.

A Classic Mopar Hood Scoop Design
In 1968, Chrysler built 50 special Plymouth Super Stock Barracudas with the vaunted 426ci Hemi. Perched atop the hood was an air scoop designed to funnel every last cfm of cool atmosphere to the hungry Hemi just beneath. Thus, the Hemi Super Stock hood was born and continues to this day to be an iconic marker for the fastest Mopars. It was so effective (not to mention, attractive) that SRT dusted it off, albeit in more aerodynamic form, for the 2018 Dodge Demon.

For this 1974 Plymouth Duster, Chris found a seller on eBay named "sc6060", who offers the iconic Mopar hood scoop design in bolt-on form for $109. Described as a Dart/'Cuda/Hemi bolt-on fiberglass hood scoop with a white gelcoat covering (the original was steel), this piece has six studs embedded in the fiberglass and with modest work can bolt to virtually any Mopar. To this, he added a set of hood pins from Speedway Motors (part No. 550-1017, $7.99), a B&B Performance High-Flo air cleaner kit from Summit Racing (part No. 72200, $49.99), and topped it off with some black-anodized billet aluminum hood-pin skid plates from Eddie Motorsports (part No. MS110-45, $103).

Hood Scoop Installation
Chris starts by sanding down the old paint on the hood to prep it for the paintjob that's coming later. Use a 6-inch dual-action sander with 220-grit discs, then work your way up to 320-grit. This will level the paint while giving the build primer something to stick to.

There's a small chip in the paint that went down to the sheetmetal, and this is the time to repair it. For this Chris mixed up a small square of Evercoat body filler with a dab of hardener.

Here, Chris uses a small spreader card to evenly fill the depression of the chip. It's preferable for the filler to be just a bit proud of the surface as you'll be leveling it after it hardens.


After allowing it to dry 5 minutes, Chris sanded the Evercoat-filled divot flat with the dual-action sander and 320-grit. Good as new!

With the hood mounted on the car and indexed so that the body gaps are all even, screw in the carburetor's air cleaner mounting post and carefully lower the hood until it leaves a small mark on the bottom of the hood. This impression will become the center of your circular hood cut.

With the center marked on the bottom of the hood, center the air cleaner lid on that mark to scribe the lid's outline on the bottom of the hood.

Using a 3-inch cut-off wheel, slowly work your way around the circle, cutting a shallow channel first, then cutting all the way through.

Now it's time to turn our attention to the hood-pin kit, which Chris picked up at Speedway Motors for $7.99. The parts we're using here are the pins, nuts, and through-bolts. The skid plates were used for placement, but Chris decided later to go upscale with a nicer-looking set of billet-aluminum CNC skid plates from Eddie Motorsports that we'll show you in a moment.


On the 1974 Plymouth Duster, the factory hood bump stops are a perfect location for the new hood pins but must be enlarged after the bump stops are unscrewed from the fenders. Use a half-inch drill bit to create the required clearance for the hood pin through bolts.

After attaching the hood pin through bolts to the fender using the nuts and washers in the Speedway Motors hood pin kit, Chris checks the vertical alignment on both pins using a bubble level.

The hood pin through bolts must pass through the hood reinforcement stamping. The Eddie Motorsports skid plates have small nuts that must be held in place to attach the plate to the hood, so Chris cut away a small section to gain access from underneath the hood.

With a piece of masking tape, lower the hood gingerly to create a small witness mark with the tip of the through bolt, then drill a small pilot hole followed by the full-sized half-inch hole. If you measured carefully, the hood should lower right into the through bolt holes.

This is the rubber gasket from the Eddie Motorsports skid plate, and Chris is using it to mark the pilot holes for the small attaching bolts. These holes are then drilled out and the plate is attached to the hood with the rubber gasket sandwiched in between.


Chris sourced his Hemi Super Stock hood from a seller on eBay named "sc6060". It cost $106 and is constructed of hand-laid fiberglass with a white gel coat. It has six small studs imbedded along the bottom edge that will be used first to mark the attachment holes on the hood.

On Mopars, the engine is always offset to the passenger side by a couple of inches, so the hood scoop needs to be centered by measuring from the edge of the hood, not the center of the air cleaner. Once you're satisfied with the centering job and the aesthetic placement mark the location of the hood scoop studs on the top of the hood.

After marking the six mounting hole locations, drill them out from above. Of the six holes, the two rearmost ones will exit in the blind area behind the hood skeleton.

From under the hood, use a -inch holes saw with a guide bit to make a hole large enough to get a socket through it. The centering hole-saw bit will make it large enough to get a ratchet socket in to tighten the hood scoop down.

Moving back to the hood, Chris is closing out the ugly cosmetic gap resulting from the circular cut. Here, Chris is using a MIG welder and a strip of 18-gauge mild steel to close out the gap wherever the hole intersects the hood skeleton.


Grind the MIG welds around the air-cleaner opening flat, fill the low areas with a skim coat of Evercoat, and level the area around the opening with the 6-inch DA sander and some 320-grit.

Since the engine compartment and engine is already painted trim black, Chris is painting the underside of the hood to match. (Yes, we know Mopars had body-colored engine bays and hoods, but that's what Chris wants!) If you're going this route, prep the underside for paint with some light sanding from a Scotchbrite pad.

Trim Black by SEM is a favorite at the HOT ROD Tech Center for use on undercarriages and engine bays and is mixed in a 1:1 ratio with reducer. Chris used acetone as a reducer, which is acceptable for use with this product.

Using an inexpensive Harbor Freight HVLP gun, Chris first coated the top with a coat of high-build primer to bury the overspray on the bottom, then turned his sights to the bottom and sprayed the SEM Trim Black.

A parallel procedure was shared with the hood scoop, first getting covered on top with high-build primer, then the bottom with SEM Trim Black.


Using half-inch nuts and some washers, Chris bolts the Super Stock air scoop to the Duster's hood. Note how the air cleaner and base have been treated to the same SEM Trim Black paint as the rest of the engine compartment. It's not the way a Mopar purist would do it (body-colored) but it looks rad nonetheless!

The billet aluminum Eddie Motorsports hood-pin skid plates are a huge step up from the ones in the Speedway Motors hood pin kit, but when you see the paintjob Chris is doing on his Duster, you'll agree the extra cost is worth it.

Even though 1974 Plymouth Dusters never came with 1968 Barracuda Hemi Super Stock hoods, it sure looks good here, don't you think?

All murdered-out, the small-block Magnum 360 V-8 looks bitchin. Now it can breathe much better too.