Grill Opening/Air intake

The Chevrolet Trailblazer SS has an "airbox" that is close to useless because of a couple major flaws.

Updated: A few months later after seeing 2/10 gains in the quarter mile by removing right headlight at the Nat's, I decided to cut MORE. See Phase II below

The intent of the intake system was to be a box sealed from under hood "hot" air. The box would be fed with cold air entering a grill opening near the passenger side headlamp.

The two problems with the airbox are that its not sealed very well from the engine compartment and the opening near the headlamp is too small to feed any real amount of cool air to the air filter.

If you examine the airbox you will notice it sits on top of the windshield washer tank and has large openings that allow under hood hot air to be sucked into the box. The under hood temps can be double what the ambient air temps are. So if you are sucking HOT under hood temps your truck is going to pull ignition timing (to protect the engine) and drastically affect performance.

One of the easiest free mods you can do is to enlarge the opening that feeds air to the airbox. If you look at Figure 1 you will see a green circle. This is the exact size and location of the opening going into the airbox. Small isn't it?

The red square shows the potential opening available which can be seen better in Figure 2. Using a die grinder you can remove the back and the side gussets which allows more air to enter the intake system. See Figure 3. How much does it help? Who knows !

The airbox is still not sealed well and sucks hot air from under the hood. As a matter of fact the opening in the front of the airbox sits right next to the exposed radiator.

Phase II (cutting again/more)
May 08, 2008

This is the second attempt at increasing air flow.

The 4 points restricting the flow of air :

* The mesh grill opening (something I am not ready to remove yet...)
* The opening in the center of the headlight which stock is an extremely stupid small hole (see figure 2 above)
* The plastic support behind the headlight
* The airbox front

Figure 4 shows the plastic panel behind headlight. This is factory untouched.

Figure 5 showing airbox trimmed on front. Notice green line showing original opening.

Figure 6 shows the airbox through new opening. Notice there is visibly more filter showing. See green line.

Figure 7 is the actual headlight opened up.

Although I never felt the first attempt did much, I really think this helps a little.

Still highly recommend removing the headlight at the track