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Guest Message by DevFuse

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Link on EJ-series engines, compression ratios and heads

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14 replies to this topic

#1 Guest_LeoneTurbo_*

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Posted 18 November 2002 - 10:05 PM


Mods: archive?

#2 Guest_synapse79_*

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Posted 19 November 2002 - 12:25 AM

Ive been trying to find out if older 2.2 heads are the way to go to replace the heads on my newer 2.2 to gain the dual exhaust port. I guess I'll have to take a look at a set of 98 2.5 heads...

#3 Guest_Legacy777_*

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Posted 19 November 2002 - 08:15 AM

I'll archive this. That data looks pretty repuatable. There's some stuff in the diff. section which I'm not sure is 100% correct.

synapse......I thought we went over this before. Just leave your heads alone. You are not going to gain anything with going to the dual exhaust heads because the valves on the older heads are smaller.

You don't want to swap an EJ25 head on, because it will reduce your compression ratio.

#4 Guest_synapse79_*

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Posted 19 November 2002 - 05:15 PM

the older heads idea was to gain performance while i had the motor out.

Eventually I want to install a ludespeed turbo when i have the $$.. the 2.5 heads would make it much more interesting..

Do you have any info on the valve size. I still think that sharing one small exhaust port between two relatively large cylinders is a larger trade off than smaller valves.

But hey, im opened minded, its just my own conclusion.

#5 Guest_Legacy777_*

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Posted 19 November 2002 - 09:36 PM

I don't know.....if you could find some flow results for both sets of heads.......that would probably tell ya what is better.

But not sure if you'll find that readily available.......

#6 Guest_wrxsubaru_*

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Posted 19 November 2002 - 11:34 PM

hey if you put a 00 2.5 head on a 2.2 turbo block would the engine become a enterfering engine? does the 2.5 liter head hocks up to the 2.2 liter with out any mayor mods? Whats the flow diffrence between the turbo head and the 2.5?

#7 Guest_synapse79_*

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Posted 20 November 2002 - 02:19 AM

Is the 00 design really an interference setup?
I dont understand why anybody would design a motor like that in the first place, is there any advantage to such a design. I like to be able to turn the motor over as needed from the crank when I am working on something. The valve springs have a way of snapping it back and forth on their own.

Anyways, unless someobody has experience or atleast or more deffinite answer, im not going to try anything right away. Maybe in the summer when i have more time, and its warm in the garage.

I imagine a head from the same year or older block is most likely to work, but I have no idea on the particulars, and it would be nice to know them before I tried something like that, like I mentioned earlier.

Ive been looking into the older 2.2 heads more, id like to run out to my buddys garage where i could compare them side by side with other heads in great detail. Problem is his shop is about 30mins in a direction i never go..
Are you certain it has smaller valves. I thought i read somewhere that the older 2.2 head was similar in desgin to the early wrx heads, which seems like it would have decent sized valves...
My gf has a 90 LS, I keep forgetting to look at the MC wires... I can tomorrow if you still need info on them..

#8 Guest_Legacy777_*

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Posted 20 November 2002 - 08:18 AM


What creates interference in subie motors is the valves hitting themselves, not the piston.

The only engines that are intereference engines are the DOHC engines.

So if the EJ25 you are referring to has DOHC's, then the answer is yes.

As far as swapping heads. The EJ25 heads will lower the compression ratio if you stick them on an EJ22 engine. The EJ25 has a longer stroke & bore.....so that's where it gets its higher compression from. Read the link posted in this thread for more details....

The EJ25 heads aren't the best idea for the EJ22T because of coolant & oil passage alignments in the heads.


I'm just relaying the info I was told from a subie technician.

I honestly can't find any info in my manuals for the valve sizing.....so I can't check really....only way would be to pull both heads off and look at them side by side.

If you don't mind lookin at the MC....that would be great.

#9 Guest_synapse79_*

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Posted 20 November 2002 - 10:26 AM

I understand now why the 2.5 is an interference desing, its because of the increased angle between the valves, to make room for the cams I guess. I bet changing a timing belt is a nerve racking experience...

New question, why dual overhead cams?

On the integra i had, it was a god send with aggressive custom cams, because it allowed you to adjust the intake and exhaust valve timing independently to gain an idle again for driving on the street. The way the honda is setup with the cams high in the motor compartment, you could adjust the cam timing in less than 5 mins with a allen wrench and a 17mm on a long extension to grab the crank(through the wheel), I must say it worked rather well.

But, if you are going to run the cams both at 0 or the same timing, it seems to me a single cam would do the job better than two (less moving parts, less weight ect..), unless there is something i dont know... ???

Does anybody make adjustable cam gears for subarus? Honda gears grow on trees...

I hadnt got as far in the comparison to look at oil and water ports and how they line up. That is interesting to know. Off the top of my head i have no idea what they look like, not that familiar, but maybe they can be oppened to line up better.

Right now im more curious about the mechanical aspects, if the timing on the cams is the same between motors, it would be bad if it were opposite, or sensors and such.. Im getting some what discourage wiht the whole idea now. Ideally what i was looking for, was to get a, yes they will bolt right on, While i had the motor out of the car.

#10 Guest_Legacy777_*

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Posted 20 November 2002 - 01:41 PM

DOHC engines.....the benefit is supposedly more responsiveness.....or better response.

You will have some flex in the cam followers on a SOHC motor. With the DOHC setup, you don't have them, so it's one less thing to have to worry about.

However with modern day materials being what they are.......I honestly don't think you are gaining tons from goin to the DOHC setup......

There may be some more to the DOHC setup then just this.....but I'm not fully schooled on it :)

The timing setup between a honda & subie is really quite different. To my knowledge there is not variable timing stuff on subies like there is on hondas.

I'm goin to use a little logic.....when settin up the timing belt and making sure everything is aligned properly. You set it to a base level.......and timing......or when spark is delivered can be varied by the ECU. But actual adjustments of the valves.....there's nothing like that....for subies.....as of now.

Read this pub1.ezboard.com/fultimat...5769.topic

#11 Guest_synapse79_*

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Posted 20 November 2002 - 05:21 PM

that is an interesting read, i'll have to go over it again when i have more time..

Im glad to see the guy switching heads let us known what he found out..

You are right that there are no variable timing stuff on a subaru, just like a stock honda. Have you seen an adjustable cam gear? It allows you to adjust the belt position(crank) in relation to the cam shaft(valves). I dont see why they couldnt be installed on a subaru...

heres a pretty good read.. kinda long

#12 Guest_LeoneTurbo_*

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Posted 20 November 2002 - 06:51 PM

Remember that Subaru abondoned the DOHC setup on the 2.5L engines for US and European markets in favor of a SOHC valvetrain in 1999...

#13 Guest_Legacy777_*

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Posted 21 November 2002 - 08:15 AM

no idea why they don't make cam gears adjustable like they've done for hondas.....may be different for how subaru sets up their stuff. Possibly because you have two separate banks of cylinders and getting the timing advanced/retarded on both banks exactly the same is more difficult and could lead to problems if something were not to go properly.

#14 Guest_synapse79_*

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Posted 21 November 2002 - 09:22 AM

I found that AEM makes them for the WRX

does anybody know if subaru maintained the same car gear design through their lines.. :)

#15 Guest_Legacy777_*

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Posted 21 November 2002 - 02:03 PM

if it's for the EJ20......which is DOHC.......it might work on some of the DOHC EJ25's.......but no tellin whether they will work on any of the SOHC models.

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