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How To: Modify your stock air intake

129167 Views 140 Replies 69 Participants Last post by  scheider1980
The community here at urges you to please use caution and seek professional assistance when performing modifications to your vehicle. Before attempting any modification it is advised that you refer to your Colorado or Canyon service manual or contact a certified mechanic as not all GMT355 trucks are the same. The staff and the associated members are in no way responsible for any damages, injuries or other harm inflicted to your vehicle or yourself which may result in attempting these modifications. The posts and content presented on this site reflect in no way the views of or it’s ownership.

A 355nation (CCP) presented by

Project Name
How-To: Modify your stock air intake

Project Description
Making your own intake and gaining a few hp

Skill Level
Easy to Moderate

Project Vehicle
Make: Chevrolet
Model: Colorado Z85
Year: 2006
Engine: 3.5L
Power windows: Yes
Sun Roof: No

Tool Needed
Tape measure, Razor Knife, Band saw or Hacksaw, ¼”NPT (national pipe thread) Tap and proper sized drill bit for tap, thread cutting oil, half round file, a good vice.

Project Time
1 hour or less

Project Cost


Metal intake pipe: $25.00
3” x 22 ½ ° pre-fabricated electrical metallic tubing (EMT) bend. (This can be found/ordered at any electrical supply shop) (3” EMT’s outside diameter is almost 3 ½”. EMT is generally made from galvanized steel, but some manufactures will make it in T304 Stainless steel or aluminum if requested, for a fee.)

Intake pipe ends: $43.00 ( hose was a 3 ft. minimum)
I ordered a length of NAPA Fleetflex Gold #644 3 ½” hose to cut for the intake hose couplings, but there are some “brand name” premade intake couplings that are made from silicon or another high heat rubber. I chose this hose because it is black and relatively cheap compared to the name brand couplings that are designed for intakes.

Clamps for pipe ends: $8.00
4; 4” (51-101mm) Stainless steel worm gear hose clamps.

Crankcase breather hose: $ 2.00
14”x ½” Heater Hose

Clamps for breather hose: $3.00
2; 7/8” (10-22mm) Stainless steel worm gear hose clamps

Crankcase breather nipple: $2.00
2”x1/4”NPT Brass pipe nipple (in the plumbing dept.)

Finish: $10.00
High quality, high heat automotive paint. (I like VHT brake caliper paint)


Remove your stock resonator box

Cut the Fleet Flex hose into two 4 1/2” lengths for the couplings.

Attach one coupling to the throttle body and the other to the MAF sensor tube with the stainless steel hose clamps.

Hold the EMT up to the two couplings and decide where you want to cut it. I cut the two straight ends off of the bend and basically just messed around with it until I was happy with the positioning/ location of the bend, then I did the final trimming so that the pipe would fit. Be sure to leave at least 1” of pipe under each coupling to allow the hose clamp to clamp to.

Decide where you want to locate your brass nipple for the crankcase breather tube, mark this spot on the pipe with a marker.

Remove everything from the truck and vacuum out the throttle body and MAF sensor tube to remove any filings that may have gotten in there during fabrication.

Drill and tap the hole for the crankcase breather nipple.

File any burrs left over from machining.

Thread the brass nipple into the intake pipe.

Sand/clean/prep all of the metal.

Paint or chrome the metal.

Put everything back together carefully so you don’t chip your paint.

Clamp one end of your breather/heater hose to the brass nipple and the other to the valve cover with the two stainless steel hose clamps.

You’re done!

Note: The most restriction in the GM 355 intake setup is the amazingly small intake hole on the stock air box behind the fender. Some people remove the box and open up this hole to allow for more airflow, I decided to close off this hole and make a completely new one on the front of the air box.(similar to the JTR cold air setup) Expect a write-up on how I did this in the near future.

Thank you, and good luck!
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1 - 20 of 141 Posts
Re: How to: Modify your stock air intake

Nice writeup!!!
Re: How to: Modify your stock air intake

thanks bro
Re: How to: Modify your stock air intake

awesome write up Tom... i love the window u put on the box lid..
Re: How to: Modify your stock air intake

i dident do a window, think that was Rawr
Re: How to: Modify your stock air intake

Very nice Tom. You are becoming a great member around here and other places. Write ups and the camping stuff. Awesome job!!!!
Re: How to: Modify your stock air intake

o crap i thought that was urs.. damn.. o well great write up
Re: How to: Modify your stock air intake

There we go!! Thanks for the insight Tom and great write up.

Question- what did you do with the vacume line at the front of the stock res.? Looks like it goes into something connected to the fuel system.
Re: How to: Modify your stock air intake

Nice going Tom!
Re: How to: Modify your stock air intake

Thanks guys!

its a fuel system vent to atmosphire, 2006 trucks dont have it. i think most people just push that hose under something so it cant be seen. i would drill and tap another nipple into the pipe if i had one, but thats just me.
Re: How to: Modify your stock air intake

Cool. I'll do that.

I should have my setup done by tomorrow. At least the custom pipe part. Got some pipes yesterday and the hose will be here tomorrow. I could've driven across town to another NAPA but I'm in no hurry. V-stack won't be here till friday though.

I'll throw a thread up to show my progress.
Re: How to: Modify your stock air intake

Nice write up.

but just wondering...

Why did you reverse your battery. i saw it in your other post but never asked, i thought about doing it to mine to make running power wires easer, but i didnt and i dont see any extra wires on yours.

.....just wondering
Re: How to: Modify your stock air intake

well, i reversed the battery because i had to. the GM mexican batteries suck. the thing died on me with 4,000 miles, after only one year from new. so anyway ;all i could find at costco ( consumer reports rated there battery as #2 best replacement automotive battery (#1 was walmart's)) was a dual (side and top post) universal battery. the side posts would hit the front of the battery box, so i decided to switch it around. i lucked out because i just recently added a winch to my truck and the side terminals had plenty of clearance to allow me to hook up the #2 gage winch wires to. by having two sets of terminals it keeps things looking neat under the hood and the top posts dont get too crowded.
Re: How to: Modify your stock air intake

That's slick as hell man....:thumbup:
Re: How to: Modify your stock air intake


*laughs evil because he is going to steal idea*
Re: How to: Modify your stock air intake

please steal it! lol
Re: How to: Modify your stock air intake

Looks friggin' awesome man! I was cleaning my engine the other night and took off the air box/silencer to clean under it and thought hmmm... I could just.....hmmm....well here is the prove my thought will work. Thanks!! :355: :salute:
Re: How to: Modify your stock air intake

Hmmm........ the company I work for is owned by one of the largest midwest electrical suppliers. I wonder how hard it will be to get one of those EMT bends. Do you by chance know the radius it's bent at? Usually it will say something like 22.5° on a 4' radius or something like that.
Re: How to: Modify your stock air intake

no clue on the radius... its EMT, all EMT of that diameter is bent to the same radius as that... its a standard. just ask for a 22.5 degree bend, they should all be the same.
Re: How to: Modify your stock air intake

Get a bunch and ship me a piece!!:lolsign: Couldn't find it down here, hopefully I'll have better luck back home...
1 - 20 of 141 Posts
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