SquidBeak

Can anyone confirm exactly what gaskets I'll need when replacing my pre-cats with gutted cats?

All of the online parts sites are very unclear about this.

As far as I can tell, it seems that I will need:

1. 20691-8J100 for the top of the rear (firewall) pre cat

1. 20691-30P00 for the bottom of the rear pre cat

1. 20691-51E01 for the bottom of the front pre cat

I don't think there is a gasket for the top of the front cat with the large opening.

Can someone please set me straight on this? I want to make sure I have the correct parts before I start this nightmare.

Thanks

Prophecy99

iTrader: (1)

wish i could help, just had a shop R/R mine, i think u r on right track, i am thinking there was some info out there on gaskets needed in a thread or two lemme look around

Prophecy99

iTrader: (1)

https://maxima.org/forums/5th-genera...g-cat-bug.html

https://maxima.org/forums/5th-genera...while-car.html

https://maxima.org/forums/5th-genera...-pre-cats.html

MaximaNoob1

I see that the front is much easier than the rear, as in terms of the honeycomb strength. So would be alright to gut the front one, but leave the back? I know someone will say do both, but if the rear is so much stronger, it shouldn't break apart, right?

Child_uv_KoRn

iTrader: (7)

Nope and nope. They're the same strength, but the front one pops loose and rattles around. A few members have posted that their rears were in pieces (it usually is the front, first, though). Half-assing **** never fixes anything.

MaximaNoob1

Child_uv_KoRn

iTrader: (7)

Might as well buy the dirt cheap altima headers and have the Y pipe modded to work.

Max139617

iTrader: (9)

If you would like to make your life easier I have a front pre cat that I could sell you which you can gut off the car. Shoot me a pm if interested

Prophecy99

iTrader: (1)

search maximanoob there was a thread on only doing one or the other

MaximaNoob1

Ok, my bad.

MaximaNoob1

The front isn't the issue for me, it's the rear one.

MaximaNoob1

****, I also didn't know Altima headers didn't fit in Maxima's. F*ck my car lol.

Reallyslowrio

4th gen headers fit. You just have to plug the egr port and the extra O2 sensor hole.

MaximaNoob1

No flange modification needed? Cool, I'll look into a set of those on eBay.

Reallyslowrio

I've been researching this for the past few months, just haven't pulled the trigger yet.

Apparently the blocks are the same from 95-08, so any manifold will bolt up. The Y-pipe is the issue with the Altima headers/Y and the 04-08 headers/Y.
I've read that people have used the 4th gen headers/Y on the 5th gen no problem, and also that people have used the 5th gen headers/Y on the 5.5 gen no problem.

MaximaNoob1

Hmmm, hopefully someone else who has done this can chime in.

Child_uv_KoRn

iTrader: (7)

That's correct. 4th gen is nearly the same as 5th. The catback will even work, technically. It's just too short.

maximatech12

Do ya just install spacers afterwards for the HO2S?

This keeps the output mV within the correct range?

do the de-foulers have valves in them?

SquidBeak

Just looking over this thread I started.

How did it go from precat gaskets to 4th gen Altima headers?

SquidBeak

Could anyone answer the question in my original post?

Thanks

Prophecy99

iTrader: (1)

why dont u just buy every gasket you think you may need, then return what you dont need?

Prophecy99

iTrader: (1)

i have some ring gaskets laying around from this project still from the shop that didnt use or reuse / everything

SquidBeak

I have the 3 gaskets that the parts catalog shows.

I think there should be a 4th gasket of some sort, that should mount on the large opening of the front pre-cat. I really want to be sure I have everything before I start this.

Can you post a pic of the gaskets you have?

Prophecy99

iTrader: (1)

sure once I get home, i may have stashed them somewhere, no promises but i can try!

SquidBeak

If anyone is interested, the 3 gaskets I listed in the OP are all that is needed.