Looking hard at my '04 Silverado I noticed that I can see pavement directly through the engine bay, underneath the factory air filter box. I pulled the box apart and removed the lower box half from the metal base mount, its just held on with grommets. The base mount is just a piece of sheetmetal. Why not take a hole saw to the filter box base and the mount together? Plenty of room for 4" or so. Then a tube straight down to a 90* elbow facing forward. The factory fog light location is a great "inlet" when cut out. You could use metal vent duct from HD or even the large rain gutter downspouts. Very cheap, very simple and probably pretty damned effective too. I'm going to get my holesaw kit.....

RT

 

I think it is one of those things that look good on paper, but not good in real life. Think of all the *&^ that you will suck up underneath your truck. ALOT of water, snow, salt, dirt, grime, dust, ashpalt, paint, etc

 

I had the same thing done and it worked good but I was constantly cleaning my air filter cuz a lot of dirt and bugs were thrown in there. I could put my hand on the tip of the intake and have some one give it gas and it would suck my hand!! That is how good I had it sealed. The best thing though I have done is remove that sheet metal and put a CAI there and the fender would create a jet stream up to the filter. I know cuz the bottom of the filter would always have some dirt, not much but some.

 

Well, I went ahead and did it. I used 4" aluminum duct and a 4" elbow to complete it, as I already had them lying about. Wasn't very difficult, cut 4" hole in bottom of filter box, mount plate and in "fog light" bumper recess. I probably could have used a commercially available hose/duct from Spectre or ramairbox.com but if I like the result I can always upgrade. The pipe is offset at a 45* angle out towards the wheel and up from the "fog light" opening, then through a 90* elbow that is twisted off to 110* or so and then pretty much straight up and back to the bottom of the airbox.

Regarding the debris issues: I didn't seal the tubing airtight to the box or the bumper and I didn't close the factory box inlets off either. My thinking is I don't want to create the ONLY pathway for air, just another good flowing opening. Not going for a "ram air" effect, just cool air. Given this is a street truck, never offroad, and we don't get much snow here, mostly rain, I am not too concerned about it. I will keep an eye on it and see if too much or any crud collects in the box. Think of it as an experiment.

RT

 

Well I didnt seal mine niether. I know I said I did but I meant the ram air tube. I had the box open and I still got a lot of trash. It does work but... well you will see for urself. Very cheap mod though. I could notice a big difference WOT at 60 MPH. It would pick up quick.

 

This has been done many times. As mentioned, you need to keep it reasonably protected from the elements, but it will work.