'98 2.5L DOHC pistons in a '96 2.5L DOHC ?

[JohnM]

Hello, I'm new to Soobs and have a 96 2.5l DOHC Outback that needs the cylinders bored to .02 over. I was only able to find .02 over pistons

for a '99 2.5l DOHC from NPR. I typoed the year and it should be '99 pistons in a '96.I measured them up and found them to be .046 shorter from the pin center line to the top of the piston. Also they are .211 shorter overall.  And I think the valve depressions will still have .024 clearance, not sure though as the machine work has not been done yet and I am researching before I do it. So, is this an option? Or will I have issues. The information given by the members on this forum has helped me in the past and I am grateful.

Thank you for your help.

Edited December 12, 2014 by JohnM

[ocei77]

I'd run the math and see how much your CR is changed with the .046 difference. If the changes are acceptable to you, then go for it. The skirt length will tend to be noisier until warmed up.

Why did you not just get another block?

? what is the end desire for your build?

 

O.

[JohnM]

Thanks for the reply O.

 

The block has 218000 on it and would like to keep it going for a while longer. I suppose i didn't want to take the risk of buying a used block just to find other issues when I dug into it. The heads have had a valve job and faced. Not sure what formula to use to find CR.

 

John

[86BRATMAN]

Your compression ratio will end up at 8.9:1 with the 97-99 piston style.

[JohnM]

Thanks 86BRATMAN,

 

The style piston is actually 99-2004 what would the CR be then?   

[86BRATMAN]

If you use the phase 1 head gasket it will be roughly the same at 9.0:1. If you use a phase 2 gasket, which you can safely do with those pistons in the phase 1 block, it will be 9.4:1 which is relatively close to stock.

[86BRATMAN]

You originally state the pistons you have are for the 99 dohc, if they are they are they should have a large square-ish dish in the middle, 99+ sohc pistons are relatively flat. There may be some confusion in which pistons you have as both were used in 99, could you post a picture of which ones you have?

[JohnM]

Here is my first attempt at a url photo of the pistons:  _57_zps4ccdff49.jpg.html

 

I'm not sure what phase block I have and I have a set of FEL-PRO # 26167 PT head gaskets.

 

Thanks for help I really appreciate it.  

 

 

[86BRATMAN]

Definitely phase 2 ej25 sohc pistons, and you have a phase 1 block being 96. I highly recommend against using those felpro gaskets on your engine. Oem subaru gaskets are the best choice for these engines.

[JohnM]

Ok, ditch the Felpros and go OEM. Then I gather it will be safe to proceed with the machining? I'll check the valve clearance. I read in here somewhere a tootsie roll works good.

 

Thanks

[86BRATMAN]

To retain a close to stock compression ratio I'd run the 04-06 sti head gasket, part number 11044AA642. Assuming the heads and block are prepped correctly you won't have any future head gasket problems. You can find those head gaskets on eBay for about 70-80 for the pair shipped.