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I'm not positive what you're asking but I think you mean to say single verses dual port heads?

 

All EJ25's and EJ18's in 1996 will be dual port heads (and therefore the dual port set up exhaust I think you're asking about).

 

A 1996 EJ22 will be single port. So I think you're talking about EJ22 stuff - 1996 2.2 liter engines available in Impreza's, Legacy's, and manual trans OBW's.

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I am pretty certain that the 97 and later heads were single port exhaust. That is when they went interference. '96 and earlier were non-interference. I believe they changed the head design slightly which resulted in the interference design. Which included going from dual to single port.

 

Edit**

 

Just checked another source and it calls for the same manifold gasket for 95-97 Legacy at 1st Subaru parts. They do show the same front pipe for the 96-01 Impreza though. I will have to do a bit more checking to verify this. Not sure why they would use two different heads in the same year on two different models.

Edited by Qman

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I am pretty certain that the 97 and later heads were single port exhaust.
That's a good point - 97 would be the only "full year" that i would trust if it mattered. Single port started in 96, but I doubt all 96's are singles.

 

Did all the changes happen at the same time - timing tensioner, interference, single port? I was under the impression that single port heads did not necessarily mean interference engine.

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I think the single port came before interference, which was caused by piston changes not head changes in 97MY. The OP can qualify it more if it matters since he doesn't say why he's asking.

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Single port came before interferance. I just sold a '96 that was a single port. I asked about this a while back and was "learned" on the differences. They did go to single port heads in '96 but it wasn't till later that they became interferance (and higher HP) as well.

 

GD

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Not sure why they would use two different heads in the same year on two different models.

 

Some models built here in Indiana, some built in Gunma Japan.

 

 

For instance, My moms old 96 OBW, had a single port....Indiana built.

 

My friends (4Tes) 97 Legacy Brighton, has a dual port......Japan built.

 

IMO, the Single Port 2.2 has slightly more torque....and Roller Cam rockers :)

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