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Discussion Starter · #1 · (Edited)
Written By: Littleredmachine

This is a how-to thread on gutting the pre-cats on the b16. This is an option for those that would like to not run the risk of having them in the stock header.

Honestly, this was a bit of a pain. The final product is cool. Sounds different... especially higher in the powerband.

I would like to thank Yon (Fenderscratch) and Pat (636specman) for being absolutely awesome with this project.

The pictures are coming and will be edited into this first post.

Obviously, the exhaust is going to be a tad hot... so, make sure the car has cooled off.

This is the order we did things in:

before


removing the splash guard to get to the belt tensioner to remove the alternator.



doing something


disconnecting alternator and removing it


the heat shield that we broke every bolt off except two. we also cut it up to fuck because greg didnt want to put it back on.




what it looks like without the shield




bottom bolts for the manifold


what it looks like with no manifold


ugly fucking waste of engineering dollars


this is the ghey noise that we are getting rid of


this is the amount of shit that came out after cleverly utilizing a bunch of random tools to knock the kitties out


greg checking to be sure all the remnants were removed


after we cleaned it up a little to be sure we got all the dust out.


big ass mess in my driveway


done its back on. refuel.






this is all the work greg did all day


this is why i can express my disapproval of the b16.

(pics courtesy of Pat)


Unplug your battery and all of the clips on the o2 sensors.

Remove your front right wheel and the wheel well cover so you can access the pulley.

Remove the alternator. Start removing the bolts on the heat shield. A note about these bolts... they fucking suck. They will break. Don't worry about it... you're not putting it back on anyhow.

After the heat shield is off, you can access the header bolts. Remove those and the bolts that attach the header to the exhaust under the car.

The header should be able to be maneuvered out of the engine bay.

Now the fun part!!!

Remove the rest of the heat shield on the lower part of the header.

We used a combination of things to get the pre-kitties out... Hammer, flat-head screwdriver, wrench, some random piece of metal that Pat found in his garage...

We started with the flat-head. Use it as a chisel. Make sure you knock out EVERY piece of the pre-cat. Remember, you're trying to avoid pieces going into the motor. Get everything out of there. Use a combination of chiseling and hitting the side of the header with the hammer.

We rinsed out the header with water... not a lot. Just enough to make sure no debris remained.

After it thoroughly dried out, we reattached everything. Yours truly managed to not bolt the header to the exhaust originally... It sounded kind of cool (lol) but, make sure everything is tidied back up.

The car is not currently throwing any check engine light.
 

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I think it's pretty safe to say--that the revised QR (07+) has proved not to be plagued with the pre-cat failure. It took them 4 years of trial and error but Nissan has built a very solid 4cyl engine again.

But removing the pre-cat is still a good idea for those that want to free up some whp.
 

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I think it's pretty safe to say--that the revised QR (07+) has proved not to be plagued with the pre-cat failure. It took them 4 years of trial and error but Nissan has built a very solid 4cyl engine again.

But removing the pre-cat is still a good idea for those that want to free up some whp.
Absolutely.

The reason I originally did this was because the 07's didn't have an aftermarket header out at the time. It did prove to make a little bit of power. I dyno'd with an intake, this gutted header and a catless exhaust and made 193 hp / 194 tq.

The piece of mind afterwards was priceless.
 

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You'll have it much easier on a b15 since there is only one big precat instead of two smaller ones.
But do I still have to take off the wheel and all that? or can i just take the header off without anything first?
 

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just buy a header. we went through the stupid gutting process because there was no other option at the time. even the shitty headers that everyone buys are cheap enough to not gut your header
 

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But do I still have to take off the wheel and all that? or can i just take the header off without anything first?
To remove/unbolt the alternator, you'll need access to the idler pulley. I've managed to loosen it without taking the wheel off, but it is MUCH easier if you do.
 

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Written By: Littleredmachine

This is a how-to thread on gutting the pre-cats on the b16. This is an option for those that would like to not run the risk of having them in the stock header.

Honestly, this was a bit of a pain. The final product is cool. Sounds different... especially higher in the powerband.

I would like to thank Yon (Fenderscratch) and Pat (636specman) for being absolutely awesome with this project.

The pictures are coming and will be edited into this first post.

Obviously, the exhaust is going to be a tad hot... so, make sure the car has cooled off.

This is the order we did things in:

before


removing the splash guard to get to the belt tensioner to remove the alternator.



doing something


disconnecting alternator and removing it


the heat shield that we broke every bolt off except two. we also cut it up to fuck because greg didnt want to put it back on.




what it looks like without the shield




bottom bolts for the manifold


what it looks like with no manifold


ugly fucking waste of engineering dollars


this is the ghey noise that we are getting rid of


this is the amount of shit that came out after cleverly utilizing a bunch of random tools to knock the kitties out


greg checking to be sure all the remnants were removed


after we cleaned it up a little to be sure we got all the dust out.


big ass mess in my driveway


done its back on. refuel.






this is all the work greg did all day


this is why i can express my disapproval of the b16.

(pics courtesy of Pat)


Unplug your battery and all of the clips on the o2 sensors.

Remove your front right wheel and the wheel well cover so you can access the pulley.

Remove the alternator. Start removing the bolts on the heat shield. A note about these bolts... they fucking suck. They will break. Don't worry about it... you're not putting it back on anyhow.

After the heat shield is off, you can access the header bolts. Remove those and the bolts that attach the header to the exhaust under the car.

The header should be able to be maneuvered out of the engine bay.

Now the fun part!!!

Remove the rest of the heat shield on the lower part of the header.

We used a combination of things to get the pre-kitties out... Hammer, flat-head screwdriver, wrench, some random piece of metal that Pat found in his garage...

We started with the flat-head. Use it as a chisel. Make sure you knock out EVERY piece of the pre-cat. Remember, you're trying to avoid pieces going into the motor. Get everything out of there. Use a combination of chiseling and hitting the side of the header with the hammer.

We rinsed out the header with water... not a lot. Just enough to make sure no debris remained.

After it thoroughly dried out, we reattached everything. Yours truly managed to not bolt the header to the exhaust originally... It sounded kind of cool (lol) but, make sure everything is tidied back up.

The car is not currently throwing any check engine light.
My apologies if this has been answered elsewhere, I am in the process of trying to remove the manifold to gut the pre cats, the heat shield is the bane of my existence! With a lot of cutting & hammer chisel I’ve been able to move what’s left of it to get all of the manifold bolts off, but it seems to be impossible to remove the header/manifold without first removing the cooling fans, (I still can’t fully remove this heat shield) hopefully someone responds before I go down the rabbit hole of removing too much. Thanks in advance
 

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just buy a header. we went through the stupid gutting process because there was no other option at the time. even the shitty headers that everyone buys are cheap enough to not gut your header
Unfortunately no, on the B16 headers start at $500 and up, the B15 you can get them on EBay for less than $100
 

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there is a socket that can fit on the end of the manifold stud though I can't remember what it is...I used a normal socket before but I wouldn't recommend it.
 

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there is a socket that can fit on the end of the manifold stud though I can't remember what it is...I used a normal socket before but I wouldn't recommend it.
I did have to to remove the fans to get the manifold out, This car is a real pain in the ass to work on, I was going to sell the converters and buy a turbo kit for it but I have too many projects to go down the rabbit hole with this car
 
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