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Modify Stock Airbox???

182176 Views 199 Replies 65 Participants Last post by  GCBCummins
Hey guys i really dont wanna spend hundreds of dollars on a cold air intake...is there any free or very cheap way to just modify my stock airbox to get alot more air flow??? if so let me know..ive researched about this already and all i find is homemade cold air intakes but i havent seen anyone just modify the airbox alone..thanks and let me know if youve done it and if it helps for more airflow
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My forced cold air induction cost me $2.
If you don't have a 3-1/2" hole saw it will cost you about $40

All you do is saw a hole in the firewall location shown after folding back the insulation.
Saw another hole in the lower rear passenger side of the stock airbox.
Connect the two holes together with 3" RV dump or clothes dryer hose.
No clamps or sealing needed, the offset inbetween the holes will lock the hose in. Leave the stock air hole open.
You're done.
What you are doing is cutting into the same channel that force feeds air to your vent system.
On my test hill this mod lowered EGTs by 150°.

This is a copy of the same principal of the best air intake ever made, the Scotty.
It's no longer available, Scotty wanted to do something else.
I did this mod over 10 years ago, no problems at all. No water gets in the filter box
for the same reason it doesn't get in your vents.
Beware, this mod is loud, sounds like the turbo is in your glovebox.

Hole location


Mod installed and box pulled away for clarity below
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you can also search swiss cheese mod as well.
PSM is making basically the same thing, except he uses s smooth silicone hose. Works pretty good. It does make you notice the turbo. I put my silencer ring back in. It's not terrible, but you can't ignore it either!

http://www.psmdiesel.com/prod.php

Beyond that a lot of guys just forgo the stock box and put on the BHAF.
$109!!!!!!!!
Knew I should have patented my idea.
Better picture than mine though.
Don't like it that they blocked off the stock hole.
Problem is when the base of your windshield is covered with snow it would choke your intake.
Some folks who have done this mod saw a bigger hole in the firewall than mine and use bigger hose.
If you do it this way you have to make the hole in the airbox oval as there isn't enough room in the bottom of the filter for a bigger round hole.

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will it add any horsepower??
will it add any horsepower??
Not in the typical sense.
It will add usable hp meaning that the egts will stay out of the danger zone for longer so you can reach higher hp.
Same goes for a larger exhaust.
alright well so i got my rv dump hose..now i just gotta cut the holes and im done...i do have my silencer ring removed from the turbo..i hope this dont get too loud
I bet you'll be putting the ring back in especally if anyone sits in the passenger seat.
HOLY CRAP!! i finished now and went for a ride..and all i can say is WOW...this sounds fricken sweet!!! it sounds like a f16!!
I have a swiss cheesed box in my toolbox, if anybody wants it you can have it... i went bhaf. it's a nice whomp whomp sound now.

it always feels good to do free mods!!! glad for you man, not many more left out there, time for the wallet.
lol i know man i think this is it for the free mods...time to start openin the wallet
$109!!!!!!!!
Knew I should have patented my idea.
Better picture than mine though.
Don't like it that they blocked off the stock hole.
Problem is when the base of your windshield is covered with snow it would choke your intake.
Some folks who have done this mod saw a bigger hole in the firewall than mine and use bigger hose.
If you do it this way you have to make the hole in the airbox oval as there isn't enough room in the bottom of the filter for a bigger round hole.
I've never had an issue with snow, but I see where you are coming from. The stock hole does not get covered either.

alright well so i got my rv dump hose..now i just gotta cut the holes and im done...i do have my silencer ring removed from the turbo..i hope this dont get too loud
Glad you like the sound. Try taking out your silencer ring and see what it sounds like! It’s a trip!
so will that work on my 04.5 too? I have a S&B cool air on it, but making my Super B louder and getting more air sounds good.:headbang:
I've never had an issue with snow, but I see where you are coming from. The stock hole does not get covered either.


Glad you like the sound. Try taking out your silencer ring and see what it sounds like! It’s a trip!
yeah dude i do have the silencer ring out..it sounds SWEET..it sounds like my turbos in my glove box!!
so will that work on my 04.5 too? I have a S&B cool air on it, but making my Super B louder and getting more air sounds good.:headbang:
im not sure..im not 2 familiar with the 3rd gens..maybe someone else will chime in
I would like to do it but i dont wanna cut into my firewall. I guess i could swiss cheese the bottom of the air box.
trust me man its worth it big time!! i was thinking of not cutting into my firewall too...but its worth it and it looks cool if u do it right too!!
trust me man its worth it big time!! i was thinking of not cutting into my firewall too...but its worth it and it looks cool if u do it right too!!
Ya but when ya sell the truck you have a huge hole in it lol. I think i was going to just get a big cone filter from napa.


this is what i did to my old down pipe when i changed the turbo. I cut it in 2 places, cut the stock airbox hose to connect the pipe to the turbo and added my aircleaner. ohh and dont forget about the silver paint job. I had to move the battery tray back a few inches to clear but im planning on putting them in the back.
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