greg donovan wrote:if you can find a phase II ej25 shortblock put the ej22 heads on it will yield a CR of around 11:1. i was going to do this but now am in the process of getting a legacy turbo.
there is a guy on 2.5RS forum that did this about a year ago w/good results.
I've built two of them, but that is neither here nor there.
For this guy's situation, the first thing he needs to work out is what Ej25 crank he has. Get the part number off the box it came in. If it is a phase II crank, this is all mental masturbation for nought. If it is a phase I, it will drop right in and you can use Ej22 bearings with it.
Beyond that, you are going to want to spring the money for some custom pistons. Crawford would be the best place to get them. He can give you a custom CR since he grinds his own from blanks he gets. As others have said, you will want 10.5 or even 11:1 CR to make this endeavor worthwhile.
Then you are still left with marginally flowing heads and a 6000rpm redline. You will need to sort that out as well. But first things first. Find out what crank you have...
1974 Porsche 914 Cam Am Limted Edition AKA the Bumble Bee
1973 Porsche 914 2.0 l -Suby swap pending
1968 Porsche 911t survivor 47k original miles
2000 2.5RS daily driver.
1999 2.5RS w/ 50+ extra whp
Suby Hai!
Apparently, Axis uses EJ257 cranks, modified to fit into EJ22T blocks. I am unsure of what the modifications entail, and have yet to receive a reply e-mail yet. They want $600 for their modded crank. I think they must knife it and mic it. I don't know how you convert a crank with the thrust journal at the end to have the thrust journal in the middle.
The Phase 1 EJ25 crank has the same main bearing journal width as the EJ22T, so that's easy. The rod bearing journal width is not really a huge deal since you'll use application specific rods. But they should be the same.
EJ25 Cranks, and pistons will do the trick.
If you want custom, Crawford as MM said.
Axis has CP pistons for the turbo version of this application (yielding 8.5:1 or 9.0:1 CR depending on which you spec).
Furthermore, Pison Displacement is 2329cc's. You are neglecting clearence volume, and piston shape (so displacement will change relative to the actual size of the piston, since raising CR with a taller piston is going to actually reduce displacement in order to acheive a higher compression ratio).
Best thing to do about displacement. Assemble your shit, then measure it out yourself.
Hence my search for accurate engine specs....
I also need the volume of a USDM WRX head, and some gaskets to play with for some rough numbers about engine size and such, as well as actual compression ratios. Mainly so I can play around and see how my calculated numbers will mesh with the measured numbers.
You also need to compensate for piston speeds, and admit the limits of your bottom end. Then you need a top-end to handle the rev limit, and of course flow enough air to make a higher rev limit worth it.
Is it worth it for an N/A application? Maybe, if you run hot cams and quad throttles.
Would I? No. I see little point in dumping that much to produce something that other methods could easily provide. Of course, I'm not in the same situation as you, and you may find the 20hp gain is worth the thousand dollars you'll spend to do this.
OK, i don't know if anyone hit on this yet, but i think the pistons clear the deck with this setup, so you would have to use two headgaskets, I think they are the regular N/A 2.2 gasket and the thin 2.5 gasket. (correct me if i am wrong Matt) This will decrease your compression
About the heads,
-I would go with reground cams from Delta Camshafts. They will give you washers to go under the lifters to open the valves more, thus increasing your redline.
-Maybe switch the to 1.8 roller cams and rockers
-You might want to switch your intake valves to the IN1(from an ej18 or ej22t) from the stock IN2. It is a smaller valve which would increase the amount of air getting around it.
Questions to everyone,
-How would SVX pistons affect the CR if put into a 2.2. I have never checked the piston design of the SVX pistons at my work, SVXs are using a DOHC head and maybe they use higher compression pistons.
- By uping the CR, would you have to switch to midgrade or even premium gasoline?
-max
94 legacy Silver Touring Wagon now w/ 5spd, Ground Controls, ej20g, rear VLSD, td05, and edms.
95 impreza Rally car. 3.0 H6
88 Toyota fj62 OME lift.
Do you mean the washers will increase the preload on the valve springs thus increasing your valvefloat threshhold? Opening the valves more wouldn't increase your redline, it would actually decrease it, unless you have stiffer springs hence the shims.
No, i mean the shims that Delta sends you to put under the lifters(in the rocker assembly). So that wouldn't increase your redline? ok. so along with the shims under the lifters, you should acompany them with shims underneath the valve springs, if you are looking keeping the same, or increasing your redline?
-max
94 legacy Silver Touring Wagon now w/ 5spd, Ground Controls, ej20g, rear VLSD, td05, and edms.
95 impreza Rally car. 3.0 H6
88 Toyota fj62 OME lift.
Actually, now that I think about it, you wouldn't want to use shims under the springs, as that could prevent the valves from opening far enough. The best way would be uprated springs. I would be hesitant about using shims for more valve lift. I'd rather have a cam with a larger lobe.
