MosesGS300

Hello every one,
I have a 2005 Lexus GS300 and I have clogged catalytic converters and as I don't have much money to replace them I was looking into aftermarket cat-less exhaust manifold. The only option I could find was for a IS300 (I will link to amazon below) and I know that they have the same engine. I was wondering if you guys know if the IS300 exhaust manifold is the same for a gs300? The mounting point to the mid-pipe looks the same. My only concern is the length of it, although it looks identical.

If you guys know any cheap alternatives feel free to let me know. I would poke holes in the cat if I could reach them. My only other option is to try to unclog them with chemicals.

Thank you

Amazon -

MosesGS300

Also if I am posting in an area of the forum that isnt suitable for this question please redirect me!

Thanks,

JM

TrueGS300

Yes the cheap ebay ones for the IS will fit fine. Its the mid pipe after the catted manifold that is shorter on the IS. I was just asking about this too. However someone mentioned that the o2 bungs are wrong on some of them.

TrueGS300

Check this one out. Same thing for way cheaper
https://www.ebay.com/itm/Stainless-S...0/282526054710

Judging by the Bungs being where they are in the pics, it shouldnt run into anything

MosesGS300

Have you used this one in your gs?

MosesGS300

Have you used an is300 manifold on a gs before, if so which one? Thank you for the reply

MosesGS300

sorry I didnt quote you when replying to your post.

TrueGS300

No I haven't got one yet, still thinking about it. But this is the one a member on here has installed right now and sent the link for me. So it has been verified to fit.

https://www.ebay.com/itm/3-2-COATED-STAINLESS-RACING-HEADER-EXHAUST-MANIFOLD-FOR-01-05-LEXUS-IS300-JCE10/273504778829?fits=Model%3AIS300&epid=2295798159&hash=item3fae27ba4d:g:3T0AAOSwn01cL1Is:rk:27f:0

As I said in the first one I sent the link for, the o2 bungs are in the same places. So if you like the polished look, I wouldn't hesitate

shwalker07

I have those IS300 headers in the link above installed in my 2004 GS300. The black paint comes off fast after a few heat cycles but just reuse your OEM metal exhaust manifold gasket that sits on the cylinder head because the gasket included does not compare in quality to the OEM one.

Here is how it looks:
Attachment 504389
Attachment 504390

JustChill

iTrader: (9)

so how did you remedy connect the cat back to the header?

shwalker07

This will bolt right up to the factory 01-05 GS300 midpipe and catback exhaust with no modification needed but the lower exhaust bracket bolted to the transmission is no longer needed.

The flanges on my oem midpipe were not in the best condition and it also had pinhole leaks around the last bank 2 o2 sensor flange on that mid pipe so I bought a Megan Racing mid pipe later on which still connected right up to these IS300 headers and factory cat-back exhaust.

MosesGS300

Thank you for the images! They help alot! So you ran the old gasket and no leaks? Also I heard these headers dont insulate as good as the oem headers (Heat up the engine bay more), is this truth or a myth?

MosesGS300

Also, how long have you had them installed? I ordered those 90-degree non-fouler adapters, do they do their job? Thanks again!

shwalker07

I have had this header installed for almost 4 months now.

Yes, I reused the metal OEM exhaust gasket and no leaks but I cleaned the metal gasket very good with some brake cleaner and made sure the cylinder head was clean too. I do not really notice a difference in temperature but headers and catalytic converters can get extremely hot on any car so you will be fine. They also make header wrap which does work to keep temps down and I used that on my Supra until I removed it and found out it started to rust in some areas which I do not use that wrap on my exhaust pipes anymore.

iirc the header does come with 2 small o2 spacers but they were a straight style and I like the 90 degree ones much better. Just make sure when you install the 90 degree ones, have them angled so water does not build-up and stay stored in that spacer. You can see how I have one of the spacers angled in my pic so any build-up of water can escape back into the header.

TrueGS300

On that note, as cheap as these headers are, I wouldn't hesitate to wrap these headers while still off the car. Much easier time to do it. Lower under-hood temps, and even if years later the pipes show rust, who cares? The wrap covers it, and it would take many years to rust through if ever. I hadn't thought about wrapping them, but I think I will. I even have a lot of spare wrap in my garage!