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The chart below show's flow numbers for phase 1 DOHC ej25d heads.

Shown is before and after, stock OEM unmodified head flow numbers vs. Port and Polish, deshroud, +1mm ex. & In. Valves.

Heads where purchased brand new from Subaru and then sent to ASF machine for modifications/flow testing.
1998 ej25d. Parts #: 11063AA762, 11039AB123.



I've been catching alot of flack from people for my interest in the phase 1 heads, but these numbers help to show that the ej25d heads are very much capable of making some big power. While most people's logic is to go for phase 2 big port heads, I've chosen to step away from the norm and see how far I can take the ej25d heads.

I'm extremely happy to finally have flow numbers for these heads, I hope it aids as a comparative data point for the community.

Anyone that has used 25D heads know they are very capable. I have them mated to a 257 shortblock and they run really well. A few mechanics that drove my car estimated 330whp or so. I had dyno numbers close to that as well but they have a lot more room for more power I think.

Hopefully next year I'll be able to get some actually numbers once my SS is out of the shop.

Slightly worked over EJ25D heads are practically equivalent to EJ20D heads. I have a thread two positions below this one that display what stock EJ20D heads can do on the dyno when paired to an EJ222 block through a 4eat, naturally aspirated. The number will surprise you and solidify any confidence you have with EJ25D heads.

That's really impressive. I've been confident in 25d head flow but it's good to see it in real numbers.
How much valve lift are your going to be running with these heads?

beatersubi wrote:How much valve lift are your going to be running with these heads?

Will be running 11mm/.433in of valve lift.