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Old 07-21-2018, 04:07 AM   #2
Scooby Specialist
Member#: 216984
Join Date: Jul 2009
Chapter/Region: NWIC
Location: Coeur D Alene, ID
1996 Impreza outback


It is true that the ej25D pistons from the 96 legacy 2.5 are different than the 97-early 99 ej25d engine.

The best combo that has been come up with is this:

1. 99-2005 ej251 shortblock in good condition
2. ej22 dual port heads like from a 95 legacy with the pad style rockers so you can run the delta 230 hp cams with stock ej251/22 cometic hybrid head gasket
3. obx dual port equal length header
4. Chamber match the heads to the 99.5mm bore of the block
5. run a 98 impreza 2.5 rs ecu or 97-98 legacy ej25d ecu is similar

I had built an ej251/22 head combo with the single port heads at the time with an old school single port borla uel header, chamber matched the ej22 heads and used the hla's rocker assembly and delta 230 hp cams.

I believe what really helped is the head chamber match to the bore of the block and the delta 230 hp cams. I got pretty good gas mileage out of this motor compared to almost everyone else that built one of these.

If you would like to know more, send me a pm. I still have the single port ej22 heads from my hybrid with less than 4k miles on them with the delta 230 camps. pretty mint.

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