High compression build

Wondering if anyone else has done an N/A high compression engine build? I recently rebuilt my legacy with an 05 XT block and bottom end, 05 impreza RS pistons,RS head gaskets and I kept the 97 dohc heads.

Not that I know of, most of us want to go with the EJ22 and swap the EJ25D heads on to make a lower compression hybrid, We will then turbo those lower compression engines... I believe there was one person who was thinking about doing it awhile back but ended up scrapping the project.

Yeah I wanted to go the turbo route, but the block was free and I can't afford the rest. Surprisingly it runs great now I just need to swap it to a manual.

To answer your question, many also do the HI-compression build, known as the 'frankenstein / franken-engine' build, which is the 2.5 short block w/the 2.2 heads. Good low-end torque and mid-range; not so much up top. 10.5+ CR. That w/some Delta Cams can get you close to a low-end boosted setup.

 

BTW, did you do the #'s on your build to deteremine you final CR?

 

TD

Not yet I really want to though would be nice to know

I'm currently doing a high compression build. EJ25 block with EJ222 heads.

I support this. I'll have enough spare parts to build the ej25d/ej22e high compression frankenstein and already have the correct cometic headgasket, but mine will be a spare motor and hopefully spend most of it's life on a stand.

I support this. I'll have enough spare parts to build the ej25d/ej22e high compression frankenstein and already have the correct cometic headgasket, but mine will be a spare motor and hopefully spend most of it's life on a stand.

 

Lol mine is for my offroad project car.

Why not just deck the block? It's an old school hot rodder thing to have the mating surface (where the heads meet the block) milled away so that the piston comes up closer to flush with the mating surface? I've seen it done on tons of older motors but never on a subaru... maybe for good reason.

Because you will need to adjust the timing when you decrease the distance of the rods to the crank. After everything is said and done with adjustable cams etc I doubt the power/$ ratio is worth it.

That makes sense why I've only seen it done on older motors, just adjust the distributor to set timing. Yeah not worth it. I think the phase 1 2.2 was 9.5:1 and the phase 2 2.2 was 9.7:1 ratio. Weren't the early 2.5 9.7:1 too?

I have no clue about older models, shame there is such little tuning software for them when doing forced induction or even for gnarly N/A setups.

I did one with EJ251 block (pistons don't clear the deck, and have smaller valve indentations), thin cometic HGs, and DOHC heads. Worked out well. Definitely felt more responsive/torquey compared to the stock EJ25D. Spun a bearing though so I'm EG33 swapping this Spring.

Highest compression fusion for our cars:

 

1997-1999 EJ25D heads.

1996 EJ25D block.

 

Instant 11:1 compression ratio and no need to customize too much or get custom head gaskets to get it to work.

Your current fusion isn't bad. It should be just shy from 11:1, but still much more compression than any stock N/A EJ25.