In 1964, Ford Motor Company decided to wedge a 427 big block into a Fairlane.  It was an engineering nightmare but when they were done, the Thunderbolt was born. Many modifications were made to this car including frame, suspension, and, most importantly, true ram air.

Many people have "ram air " on their cars, or at least they think they do.  A hood scoop is a wonderful way to provide cool fresh air to a motor, however, even if you are cruising down the road at 80+MPH, there is not enough air pressure at the scoop to force air into the motor.  The problem is that air pressure is created in front of the car.  As the air  is pushed out of the way, it is forced up, down , and to the sides.  The upward motion of the air dissipating off the front of the car redirects any forward air that would be going into your hood scoop, up and over the car.  Think of it like a bug deflector, but instead of pushing bugs up and over the car, it is air flow. I received this quote in an email:
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"I have experience in the "Bug Deflector" idea.  I have an '89 Mustang with a Cervini's Ram Air hood.  I spent probably an extra $400 for the ram air kit.  From 0-30 MPH, there is very little difference and could be slightly slower.  From 30-80, you can feel a SLIGHT bit of increase.  At 80+, there is a tremendous bog due to lack of air.  I left the kit functional for only about a month.  Since then, it's taking up storage space in the basement."    Scott Fouts


     As illustrated, this means little-to-no air pressure at the scoop.  There is a solution, however, tubes can be run from the front of the car to a sealed air cleaner holder, which will give you true ram air.  The best part is, this is something you can build at home with very little time and money.

Ram Air

This is what the original Ford ram air set up looks like on the Thunderbolt.
thunderbold grill

As you can see, one set of headlights was removed and replaced with the air inlets



This is a stock Ford air cleaner.  This part was relatively unchanged from the early 70s until it was no longer needed when EFI replaced the carb.  For the most part, all makes and models of Ford vehicles had  the same basic system.


The first step is to remove the air inlet snout.  There are either two bolts or two rivets holding it to the air cleaner housing.  I found that drilling out the rivets works very well.  If you want a dual snorkel system you will need two of these.


This is the only piece of the stock air inlet snout that will be used in the ram air system.  There are three spot welds attaching this to the inlet snout on both the top and bottom.  Once drilled out, this piece slides right out off of the end.  After I got all the pieces apart, I blasted them in my blast cabinet to get everything clean and ready for reassembly.


The blue arrow points to the factory air inlet hole, and the red arrow points to the air inlet hole that I cut into the air cleaner housing.  The new hole is a mirror image of  the factory one, including tabs to help center the inlet pieces.   The new hole is placed on the other side of  the hump  (pointed out by the black arrow)  that allows the air cleaner housing  to fit over the distributor


Two things needed to be done to the air inlets.  First, I cut  the rounded tab off of one inlet so that it didn't hang down past the air cleaner housing.  This is shown by the green arrow. The second thing that needed to be done was the inlets needed to be flared out to a more round shape.  This is better illustrated below.


Believe it or not this is a vital piece  of  the ram  set up, I know it seems hokey, but you will see that this will work very well.  This is the small size coffee can.  It is a 4 inch diameter  which is a perfect fit to the inlet tubes.  It is also flexible enough that is can be shaped, but the thicker ring on the top and bottom hold the 4 inch round shape.


Once you have removed the coffee and the label, the can needs to be cut in half right in the middle.  It then needs to be elongated to match the shape of  the air inlets.


This picture illustrates the inlet  placed into one half of the coffee can.  It takes a little bending and shaping to get it in but it is a fairly good fit.  The gaps will be dealt with later.


This inside shot shows how the inlet was bent to match the round shape of the  coffee can.  It also shows  how the two parts work together to make a semi smooth transition  from round to rectangular.  This transition will be smoothed out in later steps.


I used poprivits to attach the coffee can to the inlet.  There are 4 of them, one on each side of  the inlet.  One thing that is very important is that I installed the poprivits from the inside out so that the smooth side is on the inside.   It is important that all surfaces be as smooth as possible.


Before I poprivited the can onto the inlet, I made 4 cuts on each corner of the can all the way to the first rib of the can.  This allows the metal to move more freely as the can is smoothed onto the inlet.  Note:  slight forming can be done before poprivits are installed, but most of it should be done after.


These vice-grips were used to form the can and the inlet together.  I  used a tapping motion,  as if  removing a dent, to massage the can metal up against the inlet walls.  I also used pressure from my fingers, and light hammer blows to form the two together.  It doesn't need to be perfect, just a small amount of gap.


One thing I learned was that the bottom half of the can held its round shape during forming better than the top half, because the bottom metal seal had not been removed.  One thing I would recommend is that you waste the coffee by cutting the can in half with out taking the coffee out so that the top and bottom seal can be intact during shaping.  After shaping a can opener can be used to remove the seals just as if opening a normal can.


This is a test-fit  to make sure everything is fitting the way it needs to.  As you can see, the air cleaner is really starting to take shape.  On the next page I will show you how to  seal everything up and test it for leaks, I will also discuss why I used 4" tubing, and why I am not concerned about some flow restriction caused by using an original air cleaner.

Before we continue with the construction of our ram air system, I first want to address a few issues.   The general thought with most things in life is that bigger is better.  With this thought, one might feel that  two 4 inch  inlets won't be big enough or, worse yet,  that the  3.5 by 2.5 area of the snout on each snorkel  won't flow enough air, but if we do the math we see there is plenty.   For those of you who think "math" belongs with the list of other 4 letter words that should not be said, I completely understand, please skip to the paragraph entitled Why it Works, but for those who want to see how it figures out, please read on.

The math:
The facts for my calculations:
             the opening area of  one inlet is 8.75 Square inches (3.5 * 2.5)
             one square foot is = 144 square inches.
             number of inlets =2
             Speed 60 MPH or 1 Mile (5280 feet) Per Minute
             motor size = 302
             RPM @ 60 MPH approximately 3000. I got an average if 2560 so I rounded up

So if  we take 8.75 and divide it by 144 we get  .061 square feet.   Multiplying .061 times the distance traveled per minute, 5280 feet, we get a Cubic Feet per Minute flow rating of  320.83.  That figure is for one inlet but in this case we have 2 so when you multiply 320.83 * 2 we get 641.67 CFM.   The calculations for figuring the correct carb cfm for any motor at any given RPM are as follows. CID * RPM / 3456.   If we plug in the remaining  numbers,  302 * 3000 / 3456 = 262.15 CFM  draw from a 302 at 60 MPH and 3000 RPM.  To put it another way, the ram air setup is supplying 2.45 times the CFM required by our motor.  Now all of these calculations were done assuming that flow is reduced to the most restrictive point.  In reality, that is not the way it works. A short restrictive point will reduce flow, but not to a point equal to the most restrictive points area.  If you do all the same calculations for the two inlet tubes with a 4 inch diameter each (the least restrictive point in this system) we get a CFM of 921.53 or 3.5 times the CFM requirement.  Our actual flow rate would fall somewhere in between 921.53 CFM and 641.67 CFM.  There are too many variables like tube flow rate, air filter restrictions, and  air cleaner housing shape, to easily get it more accurate than a range of potential CFM. An average of the high and low is probably a fairly accurate approximation of the actual CFM flow of our system.  781.6 CFM at 60 MPH almost 3 times the motors CFM requirements.


Why it Works:
As is addressed in my page "Efficiency -vs- Volume Increases", some of the power produced by a motor is used by the motor to run.  It takes horsepower to drive the water pump, fuel pump, and oil pump.  The same thing applies to drawing fuel and air into a motor.  With every intake stroke, horsepower produced by the motor  is used to draw fuel air mix into the motor.  By forcing the air in rather than drawing it in we are eliminating the use of that horsepower and reclaiming it at the flywheel.  Those are free horses with no penalty to fuel economy.   Another benefit is that the air forced in is cooler than the normal air under the hood. Cooler air is denser and provides more air in the cylinder with every intake stroke and improves the % burn (also addressed in "Efficiency -vs- Volume Increases") .  The last benefit is boost, up to 2 pounds of boost can be achieved at 90 + MPH.  Don't get me wrong,  Ram Air is no replacement for a supercharger or turbo charge, but still gives a small amount of boost that wasn't there before. The majority of the performance gains afforded by ram air come from large amounts of cool air entering the motor with no effort from the motor.



So here it is.  It fits well and the tubes will clear the parts of the motor.  It is now time to make it air tight, and plumb the air tubes into the front of our car.
We are now going to use plastic filler and fiberglass to seal all the holes on the air filter, strengthen the coffee can area, and smooth out the transition from round to rectangular.
Pictures and step-by-step instructions still to come.
Last modified 03/01/05




Disclaimer on Daze Tech Tips
      I am not an expert in this field. I have performed these modifications myself with very good results. I am passing along restoration and performance tips for the purpose of education.  If you are concerned about reliability or safety issues, I do not recommend that you or any other individual perform these changes or attempt to modify your cars from stock configuration except under your own volition.  I do not assume nor accept any liability for the use of this information or how it is applied.

















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