*** This mod has been revised with improved materials and instructions. ***
Please read post # 74 in this thread for the latest version of this mod.
Original instructions below:
These are the instructions for the DWV intake mod that I designed in Sept. 2005 and tested in my 04 F150. I used it the entire time I had my 04 F150 and currently use it on my 06 F150. This mod removes the restriction at the end of the snorkel inside the fender hole of the stock intake. Bill Cohron (ASEMechanic) has dynoed this mod and it produced a 7-8 RWHP gain in the upper RPMs. It does not adversely affect the air/fuel ratios since it makes no changes to the air filter box or MAF sensor location. The main advantages of this modification are: small power increase, no increased engine noise (no drone!), similar to stock appearance, very easy assembly and installation.
DWV intake mod for the 2004-2008 F150 with 5.4L engine
1. 7.5 inch length of 3 inch inside diameter black ABS DWV pipe.
2. One female-to-female 3 inch black ABS coupler.
3. One rubber downspout connector from the plumbing section of Lowe's or Home Depot. (Lowe's item number 23455.)
4. One 4 inch stainless steel worm clamp.
5. Small container of ABS pipe glue.
1. Cut black ABS pipe to length and remove any burrs from the ends.
2. Apply a light coat of ABS pipe glue to the end of the black ABS DWV pipe in a one inch wide strip. Apply a light coat of ABS glue to the inside of one end of the female coupler and immediately press the coupler into the black ABS DWV pipe with a twisting motion to fully seat the pipe in the coupler. Allow to dry 30 minutes.
3. Attach rubber downspout connector over end of female coupler and seat fully.
1. Remove stock intake tube by removing 10mm bolt holding it in place.
2. Using a large flat blade screwdriver, insert it in the joint at the end of the flex section on the bottom where the notch is in order to remove the snorkel. Spraying silicone lubricant or WD-40 in the joint will help it come out easily. Be careful not to damage the flex section or snorkel in case you need to return to stock.
3. Loosen the 4 inch stainless steel worm clamp and slip over end of flex section. Tighten the worm clamp enough that it will not fall off.
4. Insert the end of the 3 inch black ABS DWV pipe into the flex section of the intake and slide it into the flex section as far as it will go.
5. Reinstall stock intake tube and replace 10mm bolt.
6. Slide the 3 inch black ABS DWV pipe out of the flex section and seat the downspout connector in the fender hole while compressing the flex section.
7. While holding the flex section compressed, tighten the stainless steel worm clamp to hold the black ABS DWV pipe in place.
IMPORTANT: If the flex section is not compressed the DWV intake mod may vibrate or rattle.
All the components laid out:
Everything Assembled and ready to go in:
A full 3 inch inlet. No restriction here.
Here is what it looks like installed:
Here is a what it looks like installed (closeup):