i have a friend with the 2004 outback h4 cali emissions and has the exhaust that looks exactly like an h6 exhaust. 3 cats and 5 sensors single oval ports on the heads. is the h6 exhaust the same thing or is there something different about it that it wont fit? the h6 cats can be found cheaper than the ones that say there for the h4 specifically.

2004 cars issued to California had  round port heads and drive by wire throttle.

2004 cars sold  to the rest of the country are the same as 2003.

 

On 12/20/2021 at 8:11 AM, sirtokesalot said:

i have a friend with the 2004 outback h4 cali emissions and has the exhaust that looks exactly like an h6 exhaust. 3 cats and 5 sensors single oval ports on the heads. is the h6 exhaust the same thing or is there something different about it that it wont fit? the h6 cats can be found cheaper than the ones that say there for the h4 specifically.

No. It's not the same. The exhaust gaskets for the manifold to pipe is not the same part as for the H6. The muffler is also different if I'm not mistaken.

21 hours ago, laegion said:

No. It's not the same. The exhaust gaskets for the manifold to pipe is not the same part as for the H6. The muffler is also different if I'm not mistaken.

i was hoping to use the cat section of an h6 and keep the h4 rear section. this is one of the cat sections i hollowed out to get his car running again for now. you can see the port for where it mounts up tot eh engine in this picture. this is the exhaust i took off the 2004 h4 outback that i want to replace with the h6 version. are we sure its not the same?

Opposed Forces shows basically the same images for the 6 and the 4 for MY04 - images for MY05 the H6 has a very different manifold - 3 individual ports vs a single oval

I kinda think the only way to know for sure would be to get your hands (or eyes at a junkyard maybe?) on a used H6 exhaust and physically match it up - verify measurements, etc

I have a complete H6 exhaust on my garage floor, I’m not home to go look but that looks very much like it. I could pull a measurement if needed or check sensor locations  

Just check the gasket part numbers, if they’re the same then the form factors are as well and then you just need to ensure the oxygen sensor(s?) are there and in the right spot. 

5 hours ago, idosubaru said:

I have a complete H6 exhaust on my garage floor, I’m not home to go look but that looks very much like it. I could pull a measurement if needed or check sensor locations  

Just check the gasket part numbers, if they’re the same then the form factors are as well and then you just need to ensure the oxygen sensor(s?) are there and in the right spot. 

The gasket part numbers are not the same.

https://www.discountedsubaruparts.com/p/Subaru_2004_Legacy-25L-AT-4WD-Outback-Wagon/Exhaust-Pipe-to-Manifold-Gasket-Front-Exhaust-Pipe-to-Manifold-Gasket/49250540/44011AE050.html

3.0 is not listed in "what this fits" and alternatively no 4cyl listed on the "what this fits" for the ez30 gasket.

17 hours ago, laegion said:

https://www.discountedsubaruparts.com/p/Subaru_2004_Legacy-25L-AT-4WD-Outback-Wagon/Exhaust-Pipe-to-Manifold-Gasket-Front-Exhaust-Pipe-to-Manifold-Gasket/49250540/44011AE050.html

3.0 is not listed in "what this fits" and alternatively no 4cyl listed on the "what this fits" for the ez30 gasket.

The exhaust wouldn’t mean much. Infinite Subaru parts interchange even if they’re not cross listed and have a separate part number. 

Different gaskets might suggest different bolt spacing or pipe diameter though. There isn’t much else to them to vary  

aftermarket sometimes lists gasket dimensions you could possibly compare why they differ. 

I’ll measure H6 diameter if I remember next time I’m in the garage. 

17 hours ago, idosubaru said:

The exhaust wouldn’t mean much. Infinite Subaru parts interchange even if they’re not cross listed and have a separate part number. 

Different gaskets might suggest different bolt spacing or pipe diameter though. There isn’t much else to them to vary  

aftermarket sometimes lists gasket dimensions you could possibly compare why they differ. 

From what I read, one of the studs doesn't line up with the ez30 gasket.