So I have an ej18 I've been resealing to drop into my Loyale. I just put the heads back on it a few weeks ago..

 

The shop I work at has a customer that has come in with their 96 legacy outback with an ej25.

Blown headgaskets.

 

So customer is going to replace the motor with an ej22. That means I've got a free ej25 sitting on the shop floor.

 

This makes me excited.

 

So I've read up quite a bit here. The common practice is to throw ej22 heads on the ej25 block for a high compression build. I also understand that the ej18 heads are practically identical to the ej22 heads, so with that understanding I should be able to put the ej18 heads on the ej25 block.

 

Does the ej25 block have forged crank and rods like the ej18 does? And if not, what interest should I have in swapping cranks/rods/pistons as well?

 

Oh boy.

All phase 1 cranks are the same, the EJ25 crank was just offset ground down to a smaller journal size to increase the stroke. You need to keep your EJ25 crank and rods together, those rods are unique to the phase 1 EJ25.

 

I don't know anything about EJ18 heads, but my concern would be if the combustion chamber is much smaller than an EJ22 you are going to (a) starve the EJ25 for air, and ( end up with a super high compression ratio (putting in a thicker HG would fix the latter).

EJ18 doesn't have knock control. 

 

Google it until you find someone that's done EJ18 heads on an EJ25 block, surely it's been done before?

 

1. Install the EJ18 wiring harness on the entire EJ25 long block.  Only issue there is those 96's have HLA's (which I prefer myself) but require premium gas.  

97+ heads are better. 

 

2. Get EJ22 heads and bolt the EJ18 heads to it. 

 

The shop gives away customers engines?

I havent seen it done before but in theory it would work.

 

If it were me, I'd stick with the EJ18 as its already plenty of power for a loyale and as reliable a motor as Subaru ever made. Some frankenmotors bolt together and run like tops. Others seem to be plagued by demons that can't be explained, wont go away and don't make any sense.

 

Save the 2.5 for another project or part it out to get some cash for other work later on.

 

. i'm a big fan of the K.I.S.S. approach. "Keep it simple stupid" That's just me though

Edited March 3, 20179 yr by AdventureSubaru