Screamin82 Z28

I just figured I would share some of my experience in putting together a budget cold air intake utilizing the cowl of my hood.

What I needed:

18" Cake Pan
7/8" Drop Base
1/2" Phenolic Spacer
Shorter Air filter element
Weather Stripping
2x Fiberglass Sheets
Fiberglass resin
Some rattle can paint
Pop rivets
Some RTV

What I did was cut out a 12" circle into the bottom center of the cake pan, rivet it to the new 7/8" drop base while sealing the connection with RTV. The new drop base, air filter element, and 1/2" spacer were all to solve clearance issues with the distributor and hood. So some basic measurements were key to a clean install.

I laid down the sheets of fiberglass down on aluminum on the garage floor to assure flatness, resin in the area so that it would need to support itself on the hood. This left about 2-3" of material without resin on the exterior of the square in order to attach it to the hood. Once dry, placed it onto the prepped hood and put resin around the entire circumference of the plenum area. Once that cured I cut out the hole with a dremel tool. I made a 17" diameter circle in order to ensure the 18" cake pan would seal to the hood.

Now that this was done I had to cut, trim, etc the cake pan to approximately a 1/2" clearance to the new flat cowl surface on the hood. Taking a little at a time to insure that I don't take too much off. Once completed I painted the pan, and placed weather stripping around the edge of the pan so that it would seal to the new cowl plenum.

A key here is that I can get away with such a short weather stripping because I have solid motor mounts. If that were not the case more would have to be taken off the cake pan and taller weather stripping should be utilized so when the motor twists, stuff doesn't break.

Done and done!! Any questions let me know. I skipped some steps, but all in all it was a pretty easy project. I hope someone else can save a few bucks utilizing this.

Screamin82 Z28

Also on a side note if anyone is interested on real world gains of a cold air intake I am going to the dyno Friday. I will be doing a self tune session at which I will be putting the old air cleaner on at the end to see how much the numbers actually change pulling cold air vs engine bay air. Despite what I read I would be really surprised if it is more than 5hp, I think it mostly helps streetability. We shall see.

flash2042

Very nice. I always like seeing cowl hoods that actually USE the cowl, and use it right. Looking forward to the dyno results.

novaderrik

you won't see a bit of difference on the dyno- maybe a few hp at best... you need the cool air being forced into the opening by the car moving forward to get any sort of an effect from it.
unless, of course, you have a HUGE fan blowing air at 60mph over the front of the car while it's on the dyno- then you might see an effect.

Screamin82 Z28

I was more referring to cold air vs hot engine bay air, than I was about the actual high pressure air produced. I don't think enough pressure would be produced to see any noticeable gains on the street/dyno, but cold air would make a difference dyno and street just the same. I am not convinced there is much difference with cold air which is why I am going to do the comparison. People can spend a lot of money on cold air intakes, and I am just curious for what gain, if any.

anobii

It'll have the same effect as the snorkel on the factory setup if your not moving. If you get any gains at all over stock, it'll be from how free flowing your filter is.

Screamin82 Z28

I was going to use the same filter without sealing to the hood. This will cause it to pull engine bay air (how it was set up before). So the only difference should be cold air vs hot air.

redneckjoe

very nice job! im curious to see if you pick up any power. i made a "prototype" cold airpan a while back. i want to make a nice aluminum one eventually. IDK if it picked up any power, but it makes the motor run a little cooler.

Caveman305

iTrader: (8)

this isn't a "ram air" style box guys, hes not forcing any air into the engine bay, he is drawing air from the cowl by the windshield, therefore the car moving has nothing to do with drawing the cool air into the motor

anobii

Shure it does. In fact in most cases cowl induction more effectively "pressureizes" the induction path than ram air does. Depending on the frontal area of the bumper, the air slams into it and tends to "jump" over the hood and slam into the windshield. When the air is smashed into the windshield, it becomes a high pressure zone. The opening in the cowl is a lower pressure zone, so the high pressure flows to the low pressure in order to equalize. If the cowl is sealed to the induction and not open to the engine compartment, the volume of pressurized air at the windshield is much greater than the volume going into the engine, thus will have a slightly higher pressure than atmosphere in the induction path.

Caveman305

iTrader: (8)

i understand how cowl induction works

i said the car moving has nothing to do with it drawing "cooler air" from the cowl while standing still

his setup is sealed, as long as he's not sucking in hot engine compartment air from an open element anymore, he's gonna see a gain, which will only be amplified while on the street with the car moving

novaderrik

also keep in mind that the air ductwork itself will soak up heat from the hot engine between pulls, which will heat up the air coming in a little bit. the only real way to see how effective it is would be to put a temp sensor in there somewhere to see what the air temp is right before it goes into the carb and maybe use something like a G tech (or a smart phone app...) to do some timed acceleration runs on a back road somewhere from something like 30mph up to 60mph with the induction hooked up and unhooked... maybe also daily drive it for a few tanks with and without it to see if there is any mpg difference..

Caveman305

iTrader: (8)

Good point

Screamin82 Z28

I am not sure the air will be too much warmer because I will have shifted thru 4 gears before putting the gas on the floor. The air will not just be sitting in there heating up. The engine should have pulled all of the heat soaked air in by the time the petal goes to the mat. Should be significantly cooler than pulling air from the engine bay. Idk we shall see, that's what the dyno is for!

I did notice while out for a drive yesterday that my AFR went from maxing out at 12.7 to 13. Not sure if it is because it was 95 deg out yesterday and the engine was running a little warmer than usual or if because I am actually pulling colder denser air requiring more fuel. I think I am going to go up jet sizes before Friday so I can try to hit 12.8.

redneckjoe

i put one of those open top/extream air cleaner tops on and a 3" air cleaner, right after the airpan mod, and noticed it leaned out. it leaned out a lil at idle. was cool for me cause i was running slightly rich at idle.
coulda been from the fresh air,...coulda been from the air cleaner upgrade?

best of luck on the dyno! i'm curious to see the results just from a few minor changes.

anobii

Sorry, that didn't sound like what you were getting at.
What I'm getting at is the OE snorkel pulls cool air from the fender well. The temperature difference between the two sources of air is minimal. I realize that he wasn't using the OE snorkel before sealing the cowl, I was just making an observation about the differences.

In anycase it sucks you can't have it dyno'd at 60mph. That's where you'd see the most gains.

redneckjoe

any results from the dyno friday?

Screamin82 Z28

I put 260 at the wheels on a Mustang dyno with 275ft-lbs. Running 35 deg timing with my vortec heads. It took me longer than expected to tune up the car so I didn't have time to run the old air cleaner. I am kinda bummed about it, but it was also made difficult by the fact they were reading the RPM from under my hood with there pickup. Hence I couldn't close it. That all said its a pretty sweet torque curve, pretty much all in a little over 2 grand.

Oh well looks like I will have to do a track test, which will also likely be more accurate as I will be moving. This should be coming with the next month or so. I'll post up when I get results from that.

skinny z

For what it's worth, practice has shown that when reducing the inlet air temperature from 150 degrees to 80 degrees, nearly 10% in gains can be seen in output. Cold air increases output everywhere in the rev range. Under hood temps can easily approach the thermostat rating so it's easy to see the advantage of cold air induction. Remember this isn't so much power that's being made as it is power that's lost due to the hot air. Of course it'll be necessary to tune for the fresh air.
The ram air effect is a further benefit.
Nice job.
Question: What weatherstripping did you use?

Screamin82 Z28

I believe it was Ameriseal 15800 if I remember correctly. I got the profile idea from my friend who has a G8 with the Rotofab cold air intake. It seals to the hood with the same profile weatherstripping that I utilized.

skinny z

I had come across a few ideas developing this thread.
https://www.thirdgen.org/forums/carb...b-sealing.html
Although I'm still working through the engine offset (which you've solved with the laminated filler under your hood), the weatherstrip and sealing (and using a cake pan) are still the same. Finding a 16" or 18" pan isn't as easy as I thought. Looks like a mail order deal for me.
Good looking results you have there. Effective too. Too many cowl hoods and too few people using them what they're for.

Screamin82 Z28

This is the cake pan that I used. It also comes in a 16" variety.

Screamin82 Z28

Also the hole that I cut into the hood is 17" diameter. This provides plenty of clearance for the 14" air cleaner and a 1/2" overlap for the weather stripping (18" cake pan) to compress onto. Perhaps you could just make the hole larger in your hood to solve your air cleaner offset issues.

skinny z

I'm reluctant to cut into this hood. Ultimately, I may end up selling it and going back to a flat hood. Then I'll follow up on designing a cold air intake that's low in profile and will fit under the stock hood.

Screamin82 Z28

For a stock hood I think the best design is the TPI setup where it pulls the air from in front of the radiator.

skinny z

I've been thinking about that too. Problem is, once you start to build some horsepower (north of 400 hp), the 2 small filters don't have enough airflow capacity without starting to become a restriction themselves. Handy location though, and a ram air box can be incorporated in front of the rad too for even more benefit.
Check this thread out.
https://www.thirdgen.org/forums/tpi/...pi-camaro.html

novaderrik

you could still use a big round air cleaner element and use the factory TPI style intake setup- just ditch the stock filters and make an enclosure around something like a 14X4 element with a drop base to get it under the hood.. could make something pretty stealthy and effective with a flat hood.

regarding them keeping the hood open at the dyno: did you point out to them that the whole point of bringing the car there was to see how well your cold air setup worked compared to a stock setup? if all they had to hook up was a tach wire, i can't see why they couldn't find a way to run it up from the bottom of the engine by the radiator with some zip ties to keep it away from stuff that was hot and/or moving...

skinny z

What I'm finding is that even with a drop base and only a 3" tall filter element, there's contact with the hood. That's with an Air Gap intake. What's more, the filter lid gets very close to the choke horn, may be a half inch or less and that's not good for air flow. I was using a filter lid to compensate. Of course, with the cowl hood, I can use a 4" element.
Still, as I mentioned, I'd like to build an under hood cold air intake but there are a few obstacles.
Here's a pic of a cool idea but still, I doubt that I could fit that filter case.

LT1IROC-Z

iTrader: (2)

not to hijack the thread,but,i came accrossed this thread when looking for ideas for a new cold air/ram air setup,and I really like the snorkel/duct looking plastic piece at the end of the intake tube(last pic) ..anybody know what they used or where to buy one??

t-top havoc

iTrader: (3)

Try
Specter ( spelling )
Or
Speedway Motors
Jegs, Summit.

LT1IROC-Z

iTrader: (2)

yeah,ive tried looking but not sure what its called..or what to call it rather

Joe Tag

iTrader: (4)

An idea I have been tossing around is to use the stock TPI airbox. Mount 2 of the CAI filters pointing down where the inlets are.(solves the filter restriction) For hood clearance, use a single plenum CAI for carb/TBI and a tube to connect it all. IDK if you can picture it from my description, but I see it all clearly in my head.

Edit; Apparently this has already been done(probably not the cone filters though)

Screamin82 Z28

Doing something like this was in my thought process. The cowl hood I just believed would be less restrictive and cheaper (I already had the hood and those hats are not cheap) for my next motor. I would think the TPI setup is good up to 350 whp.

Joe Tag

iTrader: (4)

When people talk about how restrictive the intake setup is, the old chevelles come to mind. This air cleaner has a much smaller intake than the smallest necked down part of that air box. It's for a 396/325 hp I actually planned on cutting off the part where the rubber piece that mounts the MAF goes to open it up a little, with a larger diameter tube fabbed into it.

Screamin82 Z28

325hp is at the crank (275+- whp), and that isn't all that much by todays standards. I have a 360 I built for around $2500 that puts 260 at the wheels.

Also I believe the restrictive part is the elements not necessarily the snorkel. The elements are like 6"x6" each, for a total of 72 si of surface area. Where as a 14" dia. 3" tall element has ~130 si of surface area. That is close to double what TPI comes with stock. At least that was my main concern in not going with that setup.

novaderrik

i think even the mighty LS6 Chevelles (rated at 450HP, but actually well north of 500) used that same air cleaner if you didn't get the functional cowl induction option..

people that get all worked up over the surface area of an air cleaner seem to forget that even under full throttle, the engine is still sucking air thru 4 holes at the base of the carbureted that are less than 1.5" in diameter and have boosters hanging out in the airflow, and that at any given time only 1 cylinder is sucking in air... depending on the setup air filters can matter, but i remember a long time ago (15 years, maybe) one of the car magazines compared a whole bunch of different air filter elements of different styles on a flowbench that was corrected to some SAE standard, and even the smallest cheapest paper filter of the bunch moved more air than a 500hp engine will move.

Joe Tag

iTrader: (4)

I had to google some formulas for circumference, area and such. But heres some math for thought. 2.02" intake valves are what most people use on high performance engines.
If you figure the circumference of a 2.02" circle it's roughly 6.35" let's say you have .6" valve lift. That would be 3.81" total surface area per cylinder that the engine breathes through. Multiply that by 8, because even though only one cylinder at a time is sucking, when you get to high rpms that is not really the case. You come up with 30.48 sq" of total opening around the valves for all cylinders. Now, I'm all for letting an engine breathe, and use the biggest filters and ducting you can. (I like to use the analogy of running up a hill breathing through a straw) But I just dont think this airbox is all that restrictive.

skinny z

A few things to keep in mind.
The restrictions in the carb are supposed to be there and that restriction serves a purpose.
The velocities and pressures experienced are not the same past the filter media as they are in front of it.
Not all filter media is created equal.
As the filter becomes dirty, it's ability to allow air to pass through decreases.
It takes approximately one sq.in. of quality filter material for every 6 to 7 hp.
The filter should not represent a restriction in the flow path. It should exceed it.

Joe Tag

iTrader: (4)

Understood, The 72 sq in mentioned above times 6.5 is 468 hp its able to support by that math. Even so, I wanted to use 2 cone filters instead.

edit; sorry this is a total threadjack. But the topic is CAI on the cheap.

Screamin82 Z28

I like threadjacks/tangents, keeps it interesting and me learning. Can never get enough information. Also that math being 468hp isn't all that far off from my complete guess at 350whp.

skinny z

Published tests have demostrated that reducing intake air temperature from the underhood 190 degrees to the 80 degrees ambient temperature is good for 20 ft/lbs everywhere in the rev range. That's a hefty dose of horsepower at 6000 rpm.
It's not so much about power being made as it is power not lost.
The graph below shows an 8% increase in power from 150 degrees to 80 degrees. My modest 355 makes about 400 hp based on trap speed. I'll know soon enough if I'll be pushing closer to 430 hp once I complete my cowl hood CAI.
Ram air would be in addition to the cold air supplied.