Installing a Low-Restriction Airbox
Paradise Garage

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© 1999 Brian F. Schreurs
Even we have a disclaimer.

You're not good enough, you're not smart enough, and nobody likes you. Get over it.
Pop the hood on an LS1-powered Firbird (or Camaro) and odds are the first thing you'll see is a massive, ugly air intake. This unit is commonly referred to as the "airbox." What were the engineers at GM thinking?? They were thinking about how the Ram Air buyers had been sucked into spending a couple grand on an option that doesn't really work, so the least they could do is make our airbox look really stupid by comparison.

Fortunately there are several replacements on the market. Most of them are just "lids" -- the part you lift up to change the filter. But Modern Street & Race has designed an entire replacement airbox which smooths airflow, includes a bigger and better filter, and takes advantage of the radiator air inlet to duct in cool, pressurized air. Handmade car parts don't come cheap but if it performs as advertised, the MS&R airbox (no part no.) and K&N filter (33-2035) are worth the money. We installed these goodies on the resident LS1-powered 1998 Pontiac Firebird Formula.

The original lid comes off.
The original base is rather restrictive.
Note how much more airflow is allowed through the new base.
The new lid's airflow is far, far smoother.
The old airbox is easy enough to remove. It's mostly held on by four 10mm bolts. Remove them and set them aside; they are not reused.

Unclamp the two front clamps on the lid, then loosen the oval band clamp holding the lid to the baffles. The lid should pull off now. Look down and smack yourself for not changing the air filter more often.

The baffles are held in place by two pins that punch into the base of the airbox. Pry those two pins off with a screwdriver.

Unplug the manifold air temperature (MAT) sensor from the baffles. Set it out of harm's way.

Loosen the band clamp connecting the baffles to the mass airflow (MAF) meter. Remove the baffles. Save this band clamp; it's necessary on the new unit.

Pull the base off the car. Note there are two bumpers that position the back of the base over the radiator. Be careful not to damage these as they are needed on the new unit.

Now the new box can go on. It bolts up at the same original four mounting holes, but doesn't use the stock bolts. The kit includes two studs and two 11mm bolts, with spacers on all four. The studs are used for the inner holes and the bolts are for the outer.

Remove the rubber radiator bumpers from the original base. Put them on the same location on the new base.

Thread the studs and spacers into the bulkhead. Set the base on the studs. Slide the spacers for the bolts under the base; bolt down the base. This collection of spacers should keep the base elevated above the bulkhead so that the airbox can draw cool air both from the nose of the car and from the pressurized radiator air intake.

Install the K&N filter, pleats down. It's a tight fit but it fits.

Slide the new lid onto the MAF meter. The MAF has a notch in it; there is a corresponding notch on the rubber lid neck. This neck is held by two band clamps: the original scavenged from the OE airbox and by a new clamp included in the kit. The OE clamp goes on the lid side; the new clamp goes on the MAF side. The new clamp also has a notch in it which lines up with the notch in the MAF. No, we don't understand why there's so much effort to line up a round meter with a round hose.

Everything aligns around this notch in the MAF meter.
Use the provided wing nuts to bolt the lid down on the studs. This is a really, really tight fit, which is what you want. It will take some fiddling to get everything lined up just right but it will go together. Note that the bellows separating the MAF from the throttle body gets compressed in a big way. This is normal; don't worry about it. We plan to replace that bellows eventually anyway.

Affix the clamps on the back of the lid and tighten down the band clamps holding the lid to the MAF.

Connect the relocated MAT sensor. It's moved forward so as to read the coldest possible air; why they moved it to the passenger side instead of the driver side (where the harness is) remains a mystery. Route the relocating line above the bellows. Be sure it sits away from harm.

Gently close the hood to make sure there are no clearance issues. If there aren't, then go for a test drive!

The completed MS&R airbox looks nice.
One thing is without question: the MS&R airbox is far, far superior in appearance than the stock mess. It's also better-looking than the aftermarket lids we've seen. And while that alone will satisfy most people, we crave more. We need proof of performance gains! So far we have dyno tested and track tested (twice) this piece with inconclusive results. We'll be doing another track test in the near future so stay tuned!

Update: The results are in. We finally got more test data and there is no doubt: this airbox is worth a minimum of two-tenths and two miles per hour on a dragstrip. That should get your attention. Not bad for an airbox, eh?