Cold air inlet
 

Well, while I was installing my AC, I thought that what am I going to do with the hole in the cowl. I thought I havent done anything stupid in a while and I'm over due, so this is what I came up with.

Once the paint dryes I will post a pic of it in.

Re: Cold air inlet
 

Although I've never seen one, apparently GM offered something similar on the opposite side of the firewall for a heavy duty air cleaner inlet:

http://img202.imageshack.us/img202/6057/airinlet01.jpg

http://img23.imageshack.us/img23/4368/airinlet02.jpg

Re: Cold air inlet
 

That's cool

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Your setup looks great. I've never anyone do this before, and it works just like all the performance arrangements back in the 60s-70s pulling cool are from the base of the windshield.

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cool...notice any difference yet?

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hey you stole my idea! good work! i've been thinking cold air for the buick engine but the a/c comp was going to be in the way of a dual snorkle air cleaner so i thought why not duct into the cowl? and the grill on top will help keep out the flying squirrels. if i'm not mistaken, the 69 z28 w/ 302 engine came this way from the factory. am i right, or am i thinking about a space ship or something?

Re: Cold air inlet
 

Nice mod OK:metal:.....I think the F**D Thunderbolt had a dual setup for the engine.

Re: Cold air inlet
 

Early Chevelle's, Camaro's, & Impala's had a single 'cowl-induction' air inlet as a special option. It was a special air cleaner base/lid & the requisite ducting to the firewall cowl. It was uncommon. Today, aftermarket set-ups go for over 1K (NOS set-up's I've seen pop up for several grand).

Re: Cold air inlet
 

The big difference with the Ford Thunderbolt was the intakes were routed through the grill.

http://i.pbase.com/v3/09/553709/2/46...rboltMotor.jpg

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Is it me or was the drawings from the manual on the drivers side?

The page is correct, because the writing is correct, but I've nver seen the intake on the DS before?

I wonder if they messed on the manual?

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Re: Cold air inlet
 

I too want to do some sort of fresh air ducting. However based on observations and articles I have read the opening in the air cleaner housing needs to be huge, like REALLY HUUUUUGE, to compensate for frictional losses that are inherent with this configuration. I believe that is what Vin63 is discussing above relating to his planned modifications.

If you look at how the Z11 Impala's were done in '63, what Smokey Yunick did on cross ram Camaro's and his Chevelle and what the Nascar versions of these set-ups looked like they all used a really large opening in the air cleaner. See photo's below.

Now I know today's fuel injected engines use a long, smooth bore tube, but carburetors are different than fuel injection. The frictional losses of running a tube can add up quickly and be detrimental to the carb. Think of it as breathing through a snorkel tube, it takes more effort than normal breathing. Using smooth bore tube, not flexible corrugations on the inside of the tube, is really important also.

That's why the fine print on the following link http://www.knfilters.com/Racing/plenum.htm states the following:

Note: The custom plenum (using a 4" inside diameter tube) is recommended for small displacement engines (less than 200 C.I.) or low revving V6-V8 engines. If the engine requires more than 45 sq. in. of filter area then the plenum should not be used because the carburetor would have to be re-jetted and a loss of high R.P.M. power will be the result.

That's why, for instance, the cowl induction hoods utilize a boot that surrounds the entire air cleaner assembly, less friction = easier to breathe.

The other thing to remember about the old Ford Thunderbolt set-up is it is a forced air set-up specifically for racing. The faster you go the more air is forced into the tubes. That is very different than the cowl set-ups that are pulling the air into the carb.

Re: Cold air inlet
 

Thanks for the info John, it might be a factor, and it might not, I'm not running some 300+ hp motor, so I am wondering if it will be a big factor or not. You can only breath in as much as you can blow out, and I'm running stock ram horn exhaust manifolds. In your opinion do you think this will still affect the performance? I know the stock air cleaner I used as a donor kept funneling down even smaller, so I cut it back for more air flow, and have a high flow air filter in it.

Re: Cold air inlet
 

First off I compliment you on your idea and for your ingenuity.

I do think the size and type of connection you have used will effect performance and that the inlet area needs to be larger, but that's just my opinion and that of K&N based on the link provided above. One thing that would help would be to change from a flex hose to a smooth bore aluminum tube, similar to what is used on cold air induction set-ups for late model fuel injected motors. As discussed above it is all about pressure drop due to internal frictional losses.

That being said it should be easy to check performance though.

First thing I would do is hook up a vacuum gage and check to see if there is a difference with the cowl induction hose in place vs. being removed. Do this at idle and at about 3000 rpm's.

Next do a couple of performance runs with the cowl induction hooked up and then with it disconnected.

Next check you mileage with the cowl induction hooked up and then with it disconnected.

Note: Keep in mind however that one of the biggest advantage of cowl induction is pulling in cool outside air when the engine and underhood engine area is heat soaked. So make sure that for test 2 and 3 that motor has been up to temperature for a period of time.

Also I am curious as to if you will end up smelling combustion/fuel smell in the cab with ac or vents on and if there will be a loss of vent pressure in car. Especially when you first start up the truck, due to fuel evaporation.

Let us know how this turns out. Cool concept :thumbs:

Re: Cold air inlet
 

Thanks John, that gives me a lot of things to check on to see if I do loose any performance.
I just bought a vacuum gauge just the other day, and have been waiting to use it once I get the truck up and running again.
As far as the smell I was also curious if I would get any fuel smell in the cab, considering one of the main reasons I relocated the fuel tank to the rear was that reason, but my AC unit I purchased uses only inside the cab air, if nothing else I will block off the vents if it seems to be a problem.
When running a performance run, would you turn over the top part of the air cleaner for a third run just to see if it makes a difference? I'm pretty sure it will. I have moved out of the performance stage of my life, or at least on this project, and just wanted a good, consistent running truck, nothing that will smoke the tires off every time I take off, that’s why I have my Camaro.
Thanks a lot for sounding off, I really appreciate the good sound advice.
Derek

Re: Cold air inlet
 

Ah yea, flipping the air cleaner. That takes me back. My dad had a 1972 C20 long bed with the high HP 350. That was the first I always did we he let me take it out for a spin. Just the sound of that big Quadrajet sucking air makes it seem like another 20 HP! Thanks for the flash back :thumbs:

Yep flippin the lid might be a good 3rd change data trial. But once the engine compartment is warmed up it will be pulling in the warm air, whcih isn't "optimal" but is the way 99.9% of all carb'd. motors get their air.

I'll be interested in seeing a mileage comparison as to if any of the stuff we have talked about makes a difference.

The performance evaluation based on "seat of the pants" feel will really be hard to tell which is better.

Good luck with the "easy breathin'"... neat stuff!

Re: Cold air inlet
 

After my first drive home with the new cold air system I wasn’t too happy, it didn’t seem to effect the performance or nothing like that, it was when I opened my vents for a little air flow was the issue. I opened up the 4's and it was just like I had my ear in the carburetor, it was loud. Oh well back to the drawing board.

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No doubt the Nascar guys can't hear the carb 'cause of the loud exhaust and the fact that they are wearing helmets. :lol:

Oklahoma, I gotta say thanks for trying this, it got some interesting discussion going.

Spurred on by this post I have been designing an outside air inlet for my '65 C10. I installed some 68-69 Camaro louvers on the hood last year, the plan is to pull outside air through the hood louvers to feed outside air to the motor.

JPG files below show the concept.

Comments?

Re: Cold air inlet
 

Now there's something I would have never thought of! Just think of all the people you've inspired. Some won't do the project because of what you've learned, while others will get started tonight to get that extra bit of engine sound piped into the cab!:lol:

I've thought about doing the same thing myself with the fresh air intake, but never wanted to give up the carburetor roar with an open element air filter.

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I've seen something similar on a hemi Mopar, the guy designed it himself and even included a filter system incorporated in the hood. Your concept should work great.

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There is also another version on the 60-66 medium/ heavy duty trucks where the flexible pipe attaches to a flange on the drivers side inner fender. A steel duct runs forward to behind the front headlight. Had an inner fender off a medium duty truck from Ca. that had this on. Have pictures somewhere.

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John, that looks cool, looks like you are a CADD person also. I don't want you guys think I have given up (its not in my vocabulary) I will just find another location for the fresh air. And as for the carb sound in the cab, 20 years ago I would have loved it, but now that I have custody of my 4 year old grandson, and he rides in the truck every morning with me to day care, I don't want to do any damage to his ears at an early age, you guys know what I mean.

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Disclaimer: I like to search for topics I'm interested in, rather than just starting another thread on the same topic. :D

Now, Mark,
That is cool. I've been researching cold air intake ideas, and that fan in route is an interesting idea.
Posted via Mobile Device

Re: Cold air inlet
 

The middle of a hood on a moving vehicle is usually a low pressure area relative to the engine bay. This would be a good spot to let air OUT of the engine bay, radiator or intercooler and is used for that purpose on many sports cars. To feed air into the engine, you need high pressure, like the base of the windshield or the front of the grill or front hood edge.

If you doubt it, cut a hole in your hood and put some tufts of yarn across it and see if they get sucked in or blown out.

Re: Cold air inlet
 

people who talk about hot air in an engine compartment usually arent really clear on what that means, they have heard some explanations that make sense and then repeat them. What people are usually referring to is the pressure/volume/temperature chart that says that colder air is denser at the same pressure, and since we know engines run better with denser air (been to the mountains and seen a decrease in performance? been in cold weather and seen an increase in performance? but dont confuse barometric pressure for anything said below, that is a system pressure change that has more effect than the temperature change) they think the "colder" air outside the engine compartment will be significantly denser than the air inside the engine compartment. the problem with this theory is the effect of temperature on density vs the effect of pressure change on density.

since the air pressure is exactly the same inside the engine compartment and outside it, the density change has to be based only on temperature difference. it takes a HUGE amount of temperature change to affect density the same as even a very small increase in pressure. we also know this is true because even small amounts of boost (3-5 psi, a 25-50% increase in pressure at sea level) from turbos or superchargers affect the power of an engine dramatically. thats what forced induction does, changes the density of air in the cylinder by increasing the pressure. you get a higher effective compression ratio.

engine compartments seem like they should be extremely hot places, after all when you pop the hood after driving it sure feels hot in there. but with the engine fan turning, and especially once you are moving, the engine compartment air is only slightly hotter than the outside air, and there is no pressure change inside vs outside, so the density change of an intake outside the engine compartment vs inside is very very very small. I would be lying if I said it wasnt any change at all, because it is there, but it is very small. Couple that with the fact that internal cylinder temperatures are very high, and the inefficiency of heat transfer by convection, especially with smooth metal surfaces like a cylinder, means the slightly cooler charge will be affected more by the lump capacitance (storage capability of heat in a large dense chunk of metal) of the hot cylinder components than it could possibly affect the cylinder to cool it off.

that's very technical, think about getting a pan very very hot and pouring water into it, unless you pour in at high gpm, the pan will convert the water to steam instantly, raising the water temperature quickly without lowering the pan temperature at all. Its an even simpler concept to imagine as running your air conditioning in a truck that has been sitting in direct sunlight for hours and hours. It takes a long time, usually longer than your drive home, to cool off those interior components that are very hot, even though air conditioning air is sometimes 90 degrees cooler than the surface temps. That is lump capacitance, and convection, explained simply.

most of the improvement people feel with an intake tube is the restriction reduction and flow improvement. and the sound, that really makes it seem like you are thrashing around at 10/10ths.

cold has its place for intake cooling, forced induction motors benefit greatly from cooling that intake charge, because the pressure change of the turbo or supercharger heats up the air a lot (see a PVT chart!), an intercooler will cool it back down slightly, but an intercooler is not usually used for density increasing reasons, but because really hot air at really high pressures can cause fuel to detonate (see "how a diesel works"), sometimes before it should (see "knock" or "playing a really expensive percussion instrument")


sorry for the book. worry less about cold air and more about improving flow as some guys have said. Keep your headlights mounted where they belong. You will see a small benefit if you slug along in 2mph traffic and have the intake routed outside, because the lower speed wont bring fresh cool air into the engine compartment.