Swiss cheese airbox mod
 

New to the forum, was looking around for some cheap/easy performance mods. I've seen quite a bit of controversy over cold air intakes (some say they work great, others say they actually hurt performance).
I've found a few threads about the "Swiss cheese" airbox mod which basically turns your stock box into a cai. This is achieved by cutting a 3" hole in the airbox, then running a PVC (or other material) snorkel to somewhere with cold air. As this seems like a very easy/cheap mod to do (as well as a very old one) I was wondering if anyone could vouch for performance gains/losses?

I have a 1998 4.3 liter 4wd 4 door blazer if that makes a difference.

The factory airbox is already a CAI. If you look at the plumbing it is pulling air from in front of the radiator support. In my opinion, unless you get the parts for the CAI for under $50 it's not really worth it. All it really does is make your engine slightly louder when you stomp on the throttle.

thanks for the reply, I had found that most people said cutting a hole in the stock box had the same effect as $200+ cai kits so I wouldn't be buying one anyways. I'll check out the internals when I get home from work and see what all is going on in the factory one; some people said expanding the stock hole made a difference due to the tubing being 3" and the hole smaller than "3. I'll probably save my cash and go get a performance tune instead though.

The snorkel from the box to the core suport is the restriction but it's true cold air. I left it alone and added three 1" pieces of clear tubing from the front of the box thru the core support to reduce the vacuum in the box. Seems like dinky hose but three of them in addition to the stock snorkle gave it a nice bump in feel and it's all cool air from outside the engine compartment. The stock hole in the core suport was port matched because it did not line up perfect then enlarged for two hoses. An existing hole outside of the headlight bracket was reamed out for the third.

I'm not sure what CAI is and only pix would clear up talk about holes and clear tubing for me.

Old cars drew in air warm air from around the engine. That's bad because for every 10F degree rise in inlet air you loose about 1% power. A tube to suck in cold air from in front of the radiator solves that plus it's a higher presure area. A low vacuum is created under a car and that low is surrounding your engine. For some stupid crazy reason those aftermarket tube contraptions that mount an open filter behind the core suport get called Cold Air Intakes. They are not cold but heated air intakes. Fools buy them and mount them in the low pressure area. The only air you want feeding your engine for additional efficiency comes from in front of the radiator. Get it however you can. I choose hose and tools I had on hand to plumb air from the proper area to a good factory box that had an undersized snorkle. They make stock snorkels small to control noise. Here is an example of a real CAI on a buggy I run. 100% of the air feeding the engine is in front of the radiator. I'll post you a pic of the simple tubes I added to the Blazer if this rare desert rain ever stops.
http://[IMG]http://i67.tinypic.com/k3xao7.jpg[/IMG]
http://i67.tinypic.com/k3xao7.jpg

I would like to see pics of the blazer as well please.

This is the tubing I used. Heater hose or Home Depot hose would work. I sized the hole saw by testing thru an old license plate and got a nice tight fit. No clamps or glue necessary if the fit is tight. Please notice my spiffy new tires in the background! Thanks to the El_Buautor with the teal green blazer in his sig for mentioning 255/70-15 fit nice in another thread.

http://i63.tinypic.com/n5re6v.jpg

I put ball point pens in the tubes so you can see the clear tubing. I removed the box and drilled thru the front for each tube. There is room for at least 2 more tubes down low that could be added later. Picture of inside of the stock air box with the three clear tubes entering obove the stock snorkle.

http://i67.tinypic.com/2v98z7s.jpg

From the top down with the lid on you can see one tube slipping past the resivior.

http://i63.tinypic.com/2w4fzo3.jpg

Thru the core suport your results could vary but this is what I did. The tube on the right of the photo is the one you can see in the last photo. I enlarged an existing hole with a die grinder. The long oval hole I enlarged below it wound up being in the way of the headlight clip so don't use it. My factory snorkel came out way low of the factory opening for it. I enlarged the bottom of that hole so the snorke gets full air flow. I enlarged the top of the hole to run the other two hoses. I trimmed the bell on the end of the snorkle to give the hoses a nice place to sit. It was getting dark on me and I just wanted to wrap up a little more air flow but I believe if you put one hose below the snorkel and drilled the core suport it should fit. Edit: It fits. See next post.

http://i66.tinypic.com/2yy81g8.jpg

There is more than one good way to skin a cat. This was free, fast, keeps sound down, looks stock and actually adds true cold air from the highest pressure area of the vehicle. I'm happy.

Just got done a driveway front end alignment to keep the General Grabber AT2's happy and decided to add more tube. One more is easy to add under the snorkle but for if some reason you want more you would have to go thru the bottom of the box. It's enough tinkering to get 4 tubes lined up an in their proper holes so I'm calling it done. Here is the hole I drilled and tube with pliers shoved in it.

http://i66.tinypic.com/k0hkb7.jpg

Pic of inside of the airbox. Addition 4th tube comes in below the snorkel. Now it's got four 1" diameter tubes along with the factory 2" hole. Not sure of the math but it's got to at least double the air to the box. Any math experts here?

http://i67.tinypic.com/155rmae.jpg

Nice, thanks for the pics! Nice tires too! So did you feel or gain anything by doing this?