Honda Fit DIY

Tools used:
jack
jackstand (i just jacked up the passenger side)

crescent wrench (for O2 sensor removal)

Just make sure you got your ratchet set with deep sockets and regular ones.. here are the main ones that i remember using
14mm (you will need a deep socket)
10mm
12mm (i think)
8mm (i think)

PB blaster – pretty sure this helped loosen the bolts to make things easy to unscrew.

Best tool tip: get a ‘cheater bar’ or a steel pipe that’s about 1-2feet long. It is possible to get the ratchet in there with this pipe over the handle, there was just enough space to move the pipe in order to loosen the header bolts. without this using a ratchet less than 1 foot long is next to impossible for my tiny arms with the bar, loosening the bolts was piece of cake

- Header : Weapon R header



The design of this looks so cool! Only street header that has a 4-2-1 that I know of. I believe the only other one that has a more ‘true’ 4-2-1 design is the Weapon R race header. Anyway, enough with the initial impressions.. onto the header removal
Before we start, make sure car is cool. I did this first thing in the morning, so all the pipes and everything was cool to touch.

1) Remove the header heat shield plate. Three bolts secure this shield. I forget the size bolt but its 8mm or 10mm.. it’s EASY. ANYBODY could do this. This was as far as I could get on the first few attempts many months ago
I’ve read that some members have had trouble with these bolts. My suggestion is to use hand tools to prevent broken bolts and other crazy unexpected stuff that could happen.

2) Unscrew the top two header nuts and break loose bottom 3 bolts.
Tip 1: spray PB blaster on all 5 bolts (2 upper, 3 lower) and let it penetrate for a good 5-10 minutes. I ate breakfast while I waited.
Tip 2: Use the pipe extension along with your ratchet and 14mm deep socket. First I put the ratchet and 14mm socket on the bolt first to get positioned to put the pipe over. I should have taken a pic of the pipe extension.. but the space used for the pipe is where you take the heat shield out. Make sure gentle smooth force is used and not excessive force or you might strip something. When it becomes loosened you’ll feel the nut break free. Once you got that part over, take off the pipe and unscrew the nut. Luckily just the nut came off for me.. I have 2008 Fit. Some other members have said the nut comes off with the stud. Not sure if PB blaster comes in to play here or gently taking off the bolts with the pipe extension.
Tip 3: Break loose the bottom 3 header bolts with the pipe extension but do not unscrew them off. This is to prevent putting excess pressure on the spring bolts that connect the header to the cat. converter. I’ve read some people have bent the spring bolts and other horror stories, so keep those 3 bolts on for now!

3) Unplug O2 sensor.
This took me a while to figure out.. I was trying to pull the O2 sensor connector, but there’s a tab underneath that prevents it from moving.
Tip 1: in the picture below, the connector on the left is connected to both an engine mount as well as the actual connector. To remove the O2 connector, simply push the tab down on the right connector and pull the plug to the right. It should come off smoothly.
Tip 2: to remove the O2 sensor plug from the mount, there’s a small tab to press underneath the plug. Press it, and then pull towards the header to remove.



[bottom of O2 sensor plug]

4) Spray PB blaster on spring bolts and header support bolts from the top of the car. I did this step right after loosening the header bolts.

you can see the PB blaster has penetrated through the header support bolt on the left.

5) unscrew spring bolts.
Tip: Just do this step slowly and alternate with each bolt to unscrew them evenly just to be safe. I did not notice any excess weight placed on the header or spring bolts, most likely because I still have 3 header bolts in place up top. Therefore, my worries about bending the spring bolts were not so high.

6) From the top unscrew the 3 bottom header bolts and remove header.
Since the top two studs remained in place, removing the three bolts was easy. If the top two studs are removed, I would suggest holding the header in one hand to support it from falling once you get the last screw off.

header removed! woohoo!

Weapon R street header comparison with stock header

7) Remove O2 sensor and replace on Weapon R header
Tip: Use crescent wrench and a little PB blaster.

WeaonR header is about 1/2″ shorter in length causing the ‘fitment’ issues. The header support mounting bracket will not reach the Weapon R header without modification. Some members have used a vice grip to flatten the mounting plate out. I did not have one and man power is not enough to flatten it..

inside diameter of stock header pipe.. looks less than 1″

WeaponR header piping diameter looks about 1.5″

Clean gasket and donut and reuse.
FF member Koi said his donut was loose on his car. Mine fit fine, but if you want to be safe you can purchase a new donut. I was going to but was too anxious to install the header luckily it worked out fine.

9) Install header, screw on top nuts and lower bolts but do not tighten.
Make sure to reuse the header gasket and put it on over the header studs correctly.
Tip 1: while reinstalling header, hold onto the donut while you lower it back in to prevent it from falling out.

10) Screw in spring bolts
Tip1: give the cat pipe some support and push it forward towards the header to allow the spring bolts to thread into the header. I did not have trouble threading them in, I carefully screwed each spring bolt evenly until both were in completely as seen in the pic below.

Original header support bracket was not reused since I did not modify it to fit. But it did feel as if there is enough support from the header bolts and the cat pipe.. I hope.

11) Reconnect the O2 sensor plug and tighten all header bolts.

Tip: Fatory specs for these header bolts are 33 lbs./ft. Unfortunately my torque wrench was too big to long to fit, so I torqued it as much as I could without the pipe extension. I’ll probably get a smaller torque wrench to torque it to specs later on, but it feels pretty secure to me.

12) Make a final check.. header bolts are tightened, and spring bolts are tightened, O2 sensor is screwed securly in header and O2 sensor plug is mounted and reconnected.

13) moment of truth.. start the engine to test for leaks..
YouTube – Honda Fit – Weapon R header – PRM intake – Spoon ETD – Beatrush Underpanel
woohoo! so far so good no leaks..

Final thoughts:
What makes this whole experience a successful one is the pipe extension. I did not attempt to use this the first few times before. So using a small ratchet with barely any torque seemed next to impossible removing those header bolts. It felt like I was going to either break the ratchet or the bolt. With the pipe extension, it greatly reduced the amount of effort needed to loosen the bolts.

Most of the tips are learned through other forum members experiences. So I was just being extra careful not to repeat some of the horror stories since I do not have quick access to repairs and parts.

Overall, header removal was not as bad as I expected. Only real challenge was removing those stubborn header bolts. And below that, was probably disconnecting the O2 sensor plug from the connector and the mount.

Expected time to remove and install header with all the knowledge above: less than 2 hours

Length of time it took me: 4-5 hours