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my home brew Cowl induction hood

Simon 88YJ94XJ

NAXJA Forum User
Location
Virginia
I saw a cowl induction style hood for the XJ in the quadratec catalog recently and thought "hell I can do that" I had a spare hood lying around and was looking for something to do with my cheap HF flux welder.

It's not just for looking purdy, when it's finished the intake tube will draw cool air from the passenger side of the opening, while the driver side vents hot air from the manifold side of the engine. Okay and it's also for looking purdy

Hopefully the pics work right, and I don't get flamed for being a newb, oh and these are thumbnails click for full size.
The victim:

I started by masking a line that mimic's the existing raised portion of the hoodline, and cutting it with my super cheapo air cutoff wheel.

I cut the rolled seam at the cowl underneith. The panel glue that holds the hood metal to the crossmembers was pretty easy to pop loose with a putty knife. Be carefull to find EVERY glue spot before you bend the "hump" out too much or you'll end up with a nasty crease in the sheet metal.

I made the sides of the new "hump" with a couple scraps of 16 guage sheet being carefull to make sure they were mirror images of each other. I then used temporary wedges band sawed out of 2x4 to get the hump shaped close to my side profile pieces. Once I had the hood line where I wanted it (where it needed to be to mate up with the new sheet metal profiles) I welded in permanent "spacers" at the cowl that will also serve as mounting points for the mesh grill I will put in later. They can be seen in this pic:

This sounds easy but there were a lot of descisions and visualizing and measuring going in here. The supports keep the cowl portion of the hump from deforming and flexing and the middle one serves as a divider between the intake "cool" side and the hot manifold exhuast side. It will be boxed and seam sealed later to allow the cold air tube/housing (which I'll be making) to seal completely. After tacking the profiles in place I stitch welded them... Okay actually I foolishly tried to bead weld but the sheet warped badly (as you'll see). The stich welding happened after I cut the welds out and restarted. the paint was removed from the warpage in preperation for the gobs of bondo it would need:

GOBS O BONDO well not as much as it apears, this's actually a pretty thin layer (many thin layers):

It got sanding primer after an embarrassing amount of sanding re-mudding and sanding again due to my oversanding nature. and my personal pride in wanting it to look good even if it is going on a Cherokee (with plenty of imperfections), and even though it's being painted in a shop with various metal, wood and landscaping operations going on, all creating dust.

and more sanding until I felt a little silly about how many hours I was putting in making this thing smooth... Until I finally called it good(enough). Shooting color was almost anti-climactic, but the Fall Ladybugs flying around kept me on my toes... and caused several "paint problems" including the distinct inprint of a razorblade where I accidentally droped one on the first coat. The color which is a factory match; matches my 12 year old XJ's pretty well (this is SW 2nd Dimension 3 part single stage base which was fantastically easy to work with and sweet results in a dusty enviroment):

I'll have some before and after pics soon, this blury sideshot was done late while in a hurry to get back home to the Wife:
 
Dude, you rock! Excellent contribution.

This is by far the best low buck approach I have seen. I am going to shamelessly copy this exactly. Please post up the screen and intake hook up when you get there.

Thanks for taking the time to write this up and share it with the rest of us.
 
Very good work.

Do you have any ideas for sticking a grille or something in the new opening?
 
Beautiful, I'm going to do this as well.

Verty nice!!
 
G.Nenzel said:
Dude, you rock! Excellent contribution.

This is by far the best low buck approach I have seen. I am going to shamelessly copy this exactly. Please post up the screen and intake hook up when you get there.

Thanks for taking the time to write this up and share it with the rest of us.

Thanks for the kind words, copy away, I will have more on this I'm rounding up the tubing and seals for the intake. which I'll get off ebay more than likely.

The grill will be Stainless or Aluminum perforated (round holes) sheet metal also off ebay which I'll powedercoat black.
 
G.Nenzel said:
Are you planning a flexable connection or a gasket to the underside of the hood?

I'm going to go with the gasket, using the rear hatch seal off my parts cherokee (where the hood came from), I'm pretty sure on making a sheetmetal housing that the air filter will fit in, similar to most cold air pipe "heat shields" do with weather strip to seal to the hood.

The part I'm not sure about is how I'll attach it securely to the 4.0 valve cover... I may swap a 4.2 valve cover I have lying around (from my YJ's 4.2 to 4.0 HO head conversion) and use the triangle of bolt holes it has for the old carbureted air cleaner housing.

The other and my favorite option is a sheet metal valve cover fab with a machined base, that would allow welding and also allow me to change the filler tube and PCV gromets necking them up higher with machined surfaces so they don't leak any more...
 
great job, care to elaborate on the the paint you used, brand, cfm used, compressor specs, type of spray gun, etc. reason i ask is i want to spray some paint but advice is all over the place as far as recommendations. sounds like you did not have perfect conditions, and yet it looks great.
 
Looks real good, makes me want to go fix mine and add a nice curve to it.
 
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