I decided a while back that I wanted a cowl hood to try and lower underhood temps and drag in fresher air for the tymar intake. No one made (at least that I could find) a 4" cowl hood for my 01 superduty, so I decided to order up a nice smooth top scoop that really is a 3 3/4" but its clearly taller than anything else I've seen. So this is the first installment to show how its done. I don't know if people even care or want to see how its done, so if you do let me know and I'll keep going.


The first step was to center the scoop from side to side and line the scoop lip up with the back edge of the hood.

I then mark the outer edge of the lip all the way around, remove the scoop from the hood and move the outer lip mark in 2 1/2" on the sides and 1 1/2" in on the front edge, this is where I cut out the hood skin material only, DO NOT remove the substructure, this will weaken the hood!

So Pic 1 is what it looked like after I removed the material, sanded and primed. Note that I didn't cut it right to the back edge of the hood, I left 2" of material there to retain some structure strength. I did cut into the structure to allow more room for airflow, if you decide to do the same the key is to not cut into the rib material like you see in the "diamond" center. Once you get into the upforming sections you loose structural strength fast. Could I have removed more? Yes, but the hole I stuck in there was the max I felt was safe to me. Also when doing this make radiused or rounded corners, don't make sharp corners, again more strength.

Pic 2 shows the scoop just set on there for mockup and to look at where I needed to make adjustments. When the scoop was clamped down at the back edge, the front lip was about 3 inches off the hood, oh crap, even when I pushed down HARD I couldn't get the scoop to form to the hood, why? cause the hood is curved and the scoop isn't.

Pic 3 shows, very poorly due to a yellow sharpie, where I planned to cut the scoop, Yes I said it, CUT IT. To make the flat scoop contour to the hood I made relief cuts starting at 12" from the back edge and then every 2" on both sides of the scoop.

Pic 4 shows the scoop after the relief cuts were made. I used a thin blade in a 4" grinder to make the cuts. It is very close to forming to the hood, After mocking it up again I see I need to make 1 more relief cut at 10" and grind open the relief cuts at 12, 14, and 16 so it can bend more at these points and not overlap.

So that is what I did tonight in about 2 hours. I used a sheet metal nibbler and a high speed air cutoff tool to cut the hood material, a 4" grinder with a thin metal cutting blade to cut the scoop, a 4" grinder with a sandpaper wheel to smooth rough edges, and a 4" grinder with a twisted wire wheel to prep the surfaces for primer.

 

Here's last nights progress

Pic 1 shows the scoop in place for mock up and if you look close you can see it bows up from the hood, this denotes not enough has been removed in the relief cuts, plus it needs 2 more relief cuts closer to the back. Too many reliefs is a good thing.

So once the reliefs were opened up more and 2 more cuts toward the back of the scoop were made the scoop laid down right. I then clamped down the back of the scoop where I had originally mocked up the scoop and drew lines and began to drill out and install rivets one by one alternating sides so the scoop would lay down nice and evenly.

Pic 2 shows the scoop from the side after riveting.

Pic 3 is a upper angle after riveting.

Total time at this point is 3 1/2 hrs in. Next is some slight grinding of rivet heads and the edge of the fiberglass skirt, then fiberglass mat and resin to start to blend the scoop into the hood.

 

Nice writeup keep it coming

 

So here's today's edition.

So to start tonight I mounted up a thin flex non-ferous wheel on the grinder and started to grind down the aluminum rivets to thin them, but not get so far as to weaken them enough so they fail. I also grind the edge from the rivets to the outter edge to try and get it fleathering and make the transition from hood to scoop smoother. You can see that after grinding in the first pic or 2

Next I mounted up a 24 grit flap wheel on the grinder and go back at it again and really smooth out the hood to scoop transition and the rivets. I also sand the paint away from the scoop a good ways to ensure I'm glassing on roughed up material. Never try and glass to smooth paint, rough the crap out of it for the glass to get a real good bite and remove all the wax. The next few pics show that work.

So next I cut the fiberglass mat. I like to use Bondo mat as it comes folded 4" wide, so the first mat strip you just cut on the fold at 4", makes it pretty easy. Normally I cut my 2nd layer at 6" by folding the mat so 2 folds meet and that marks off the 2" + 4" fold next to it makes for the 6", but this scoop required alot of reliefs so I have alot of messing with to get the next layer on. The next pic you can see shows the mocked pieces of mat so I know I have what I want.

So next it was time to glass, First I clean the hood and scoop 3 times with laquer thinner, just to make sure its as clean as possible and again to remove all waxes. I then mixed up resin glass in a disposable .50 paint container from home dumpo and using a 3" chip brush from Harbor Freight (like $3 for 12, toss em when your done) I "painted" a layer of resin on to the flange and out onto the hood so I knew the mat couldn't reach that far out, once it was buttered I laid the mat into it and keeping the brush wet smoothed the mat into the butter and laid a nice thin layer over the top. You have to watch for snot trails, that's when a strand comes loose and wads up and basically makes a nice f'd up spot, you have to sooth it out to the edge and pull its *** out of there. Loose fibers are fine, but don't leave lumps. Also try and brush in only one direction, that way it just lays down nice and no lumps, back and forth brushing will lump up the mat. So the final pics should show that.

 

 

Looks good, but man, what a lot of work...

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4TSNA_enUS365US366&q=cowl+hoods+for+superduty#q=cowl+hoods+for+superduty&hl=en&rlz=1T4TSNA_enUS365US366&prmd=ivs&source=univ&tbs=shop:1&tbo=u&ei=oRymTNnrB5SksQPh4uj9Dg&sa=X&oi=product_result_group&ct=title&resnum=3&ved=0CDIQrQQwAg&fp=fdfb9c54bdf6e14b

 

You miss the point,
#1 Noone makes a 4" cowl hood for the superduty. Only way to get that or a taller cowl is to do it yourself.

#2 This site is not for those who simply buy everything they want, sometimes they want to get their hands dirty. Best they have some help and see an actual install than to go it alone.

#3 Price. cheapest hood might be 300 + 100 shipping, puts you at 400 for the hood. I have 20 in a stock junkyard hood and 80 in a off the shelf scoop, plus 25 in shop supplies, at the most someone would be in for around an actual 200 at this point. You could argue your time has value, and it does, but anyone who wants to do it themselves really wouldn't care about this factor.

At this juncture actual time is around 4 hrs, and that includes looking, and measuring, and thinking, being upset about having to search for tools not being put away in their rightful places by a-holes in my shop, and the occasional beer slam for inspiration and intoxication, I'd be under 3 hrs easy. The drilling and riveting is where you loose most of your time. My 10 year old has been reading this blog and felt he could follow the directions and suggestions so far, course this is the little snot who at 9 1/2 decided to drill holes in the drywall and blow in insulation after helping me insulate the house... In the interior walls. At least now I don't have to hear his Gameboy until 2 AM.

 

Tonights update

So I let the resin cure for 24hrs and it was good and hard. I worked it with the 24 grit flap wheel and basically worked to smooth and feather the transition from hood to scoop flange and to create some surface roughness even further out for a good bite when I laid the next layer of glass.

Next I wiped the scoop and hood down 3 times with laquer thinner to ensure it was totally clean. I then laid the dry mat at a 45 to the initial direction of the mat and cut it to fit. This time the mat will go down the sides of the scoop and then about 3" away from the scoop.

I then mixed up my resin and buttered the scoop sides, the flange, and a good ways out on the hood, further than the mat reaches. Once buttered I laid on the mat starting at the top of the scoop and laid it down the side. Again I kept a wet brush and smoothed it on. Remember to work in one direction with the brush so the mat doesn't bunch.

Might sound like alot was done, but all this took about 20 minutes.

Pics again so you can see what it looks like now. Note: Being neat when "painting" is only necessary if the art teacher is watching, in glass its more important to ensure you soak the crap out of the mat so the resin penetrates in deep.

 

Lookin good my friend! Keep up the good work

 

I must say this post is very helpful especially to car owners who are not that knowledgeable enough when it comes to car. Thanks for sharing.