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Old 12-07-2005, 06:44 PM   #1
mattvct
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Default 2.5L DOHC Cylinder Head Work

Well, my engine goes off to the engine shop tomorrow, and I wanted to know if anyone has any particular recommendations relating to overhauling the cylinder heads for this car? I'm going to go for a moderate port and polish (port-match to gasket, smooth contours, remove casting lines, and blend into the combustion chamber for the most part with the exhaust side polished and the intake side textured). The entire valvetrain is getting disassembled with worn parts replaced, and I'm having the bearings swapped out for new. I'm just looking to see if anyone has any other specific recommendations based on first-hand experience (any flow bench or %VE data would be VERY much appreciated).

I'm probably going to leave the block alone for the time being since it is in excellent shape still, and I'll just keep my eyes open for a 2.5L STI block and then build that up with some 8.5 or 9:1 compression forged pistons for when I go turbo.
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Old 12-08-2005, 02:42 AM   #2
Honkey3k
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i port and polished my ej25 dohc heads for my 98 outback... 30hp to the wheels
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Old 12-08-2005, 10:27 AM   #3
Jonathan
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Ship the heads of to Cobb tuning and get a set of Cobb cams installed. Then have the machine shop do O-rings as well as porting and polishing the heads and make sure you use the heavy-duty Factory Subaru Cylinder head gaskets.

Patrick Olsen did this (along with an Injen CAI, MRT Headers, a high-flow cat and a whole truckload of other stuff as well). I think he gained a good 12-20 HP and much more useable mid-range torque.
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Old 12-08-2005, 10:35 AM   #4
Jonathan
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Quote:
Originally Posted by Honkey3k
i port and polished my ej25 dohc heads for my 98 outback... 30hp to the wheels
You managed to loose 135 HP ? Did you gain back any fuel economy ?

Thirty HP ? Damn, a 40 year old 1200cc VW beetle could produce 36 hp stock (air-cooled, with no complex fuel injection or finicky electronic controls) although it probaly lost 5-6 hp in the transaxle. Have you tried racing one of these ? (Finding a stock VW beetle to race is tricky these days).
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Old 12-08-2005, 01:47 PM   #5
Honkey3k
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are you joking right now? ur a moron... 30hp gain
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Old 12-08-2005, 01:56 PM   #6
Teh Legacy
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Quote:
Originally Posted by Honkey3k
are you joking right now? ur a moron... 30hp gain
I'll believe it when I see it.
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Old 12-08-2005, 02:03 PM   #7
Honkey3k
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lol why did i come to the legacy thread....

i have dyno sheets to prove it, i wouldnt just throw out a random number believe it or not. but that car is long gone....

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Old 12-08-2005, 02:08 PM   #8
pilfflip
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I'm not saying that a port and polish job on a set of heads from a 2.5 isn't going to gain you anything but i was under the impression that the 2.5 heads have great flow to begin with therefor not much is to be gained from the port and polish job, but be sure to let us know how it turns out for you



~Mike
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Old 12-08-2005, 02:12 PM   #9
Honkey3k
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With a full port and polish job I gained exactly 28.1whp / 35.6 wtq. i dont have a scanner but thats what it came out too. car was a lot faster obviously and a lot mroe fun to drive. then i got an rs and realized how much wasted money i put into my legacy. but it was fun while it lasted..

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Old 12-08-2005, 02:13 PM   #10
Dobes
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<edit> chopped some out.

How are the valves? Consider getting them glass beaded and have the seats ground to match.


JD
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Old 12-08-2005, 02:17 PM   #11
Honkey3k
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Quote:
Originally Posted by Dobes
30hp to the wheels? That means about 35-40hp at the flywheel which is
more than a 20% gain in power for only porting and polishing the heads.
I don't think so. I would imagine a 3 hp gain is more like it for
porting and polishing a stock 2.5L N/A DOHC Subaru motor.

Back on topic: how are the valves? Consider getting them glass beaded
and have the seats ground to match.

JD
dont know what to tell you lol. perhaps the sAFC, borla headers, full exhaust, intake, lightened pulleys, and super jdm tail lights provided what i needed to make peak hp ay?
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Old 12-08-2005, 03:42 PM   #12
Dobes
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Aaack, I tried to delete my post since I didn't want to get into this argument but it looks like I'm too late. Whatever.

Now that you mention the other mods (headers, intake, exhaust) your claims make a bit more sense. Gaining 35hp for simply porting and polishing a stock Outback engine on the other hand seems awfully optimistic. I think if that were the case you'd see a lot more people doing that to reach the 200hp n/a mark.

JD
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Old 12-08-2005, 03:55 PM   #13
Teh Legacy
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Quote:
Originally Posted by Dobes
Gaining 35hp for simply porting and polishing a stock Outback engine on the other hand seems awfully optimistic.
Eggzactly. There is simply no way to gain 30 WHEEL HORSEPOWER (~45-50 Crank HP) from a simple port and polish to stock EJ25 heads. With supporting mods? Maybe 30 WHP all together, including all other mods.

If this were the case, like Dobes said, there would be a lot more N/A tuned LGTs and RSs out there.

On another note, how much did you spend on having them ported and polished?
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Old 12-08-2005, 04:09 PM   #14
Honkey3k
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ok yea ur right, i went out of my way to post a lie lol. u guys are funny. have fun in your legacy thread.
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Old 12-08-2005, 10:17 PM   #15
Teh Legacy
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I believe I speak for all of us when I say, "Lets see some proof." Anyone can say they did anything with something which was made from nothing on the internet. We're not trying to flame you nor prove you're wrong. Personally, I'd like proof of said gains, because if the price was right, I'd be interested in doing a port and polish as well. You're not making this easy by coming in here, bragging with absolutely no proof, then spurting out such a blanket comment to us "Legacy people." Mature a little, come back, then we'll have an adult conversation about Subarus and the wonderful, head-gasket-frying EJ25.

P.S. Try using proper grammar once in a while. That way, we won't think you're a punk high schooler pulling dyno numbers out of your ass.

Oh, and us Legacy people will enjoy both our thread and our leather interior.

Jonathan
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Old 12-09-2005, 12:45 AM   #16
Patrick Olsen
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You come here and post a horribly misleading statement like...
Quote:
Originally Posted by Honkey3k
i port and polished my ej25 dohc heads for my 98 outback... 30hp to the wheels
... and you don't expect us to question that?

Now if you had given us the full story originally, like this...
Quote:
Originally Posted by Honkey3k (modified/corrected by Patrick Olsen
I port and polished my ej25 dohc heads for my 98 outback... That plus an S-AFC, Borla headers, full exhaust, intake, lightened pulleys, and super jdm tail lights provided a 28hp gain, and almost 36ft-lb of torque (dyno proven).
... then you wouldn't see everyone questioning your statement.

And I fail to see what this has to do with Legacy vs. Impreza. A 2.5L is a 2.5L. If you had made the same statement in the Naturally Aspirated Forum you would've gotten jumped on there, too.

Pat Olsen
'97 Legacy 2.5GT sedan
+40hp (dyno proven) with heads, cams, exhaust, intake, S-AFC
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Old 12-09-2005, 03:07 AM   #17
Honkey3k
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lolol
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Old 12-09-2005, 07:07 AM   #18
Teh Legacy
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Quote:
Originally Posted by Patrick Olsen
Pat Olsen
'97 Legacy 2.5GT sedan
+40hp (dyno proven) with heads, cams, exhaust, intake, S-AFC
Now THAT I can believe. What sort of heads / headwork did you implement? Cam profile? Right now I'm at a crossroads with my Legacy. I'm not sure if I want to go AFI or stick to NA. That also depends on whether or not this is going to be my soul sorce of transportation for a while.

Jonathan
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Old 12-21-2005, 03:25 AM   #19
XR8TED
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Here is a pic of a CRACKED test demo head we are playing with it is currently in the r&d stage trying to find out what works and what doesn't...

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Old 12-21-2005, 09:52 PM   #20
Patrick Olsen
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Quote:
Originally Posted by 97legacygt
Now THAT I can believe. What sort of heads / headwork did you implement? Cam profile?
I have the Cobb Stage 1 heads and Stage 1/Street cams. Since I did my stuff (back in '02) I believe I've read here (over in the N/A forum) that one would actually see more gains with the Stage 2 cams and stock heads. I think it was Matt Monson who said that, so you might try searching over in the N/A forum for something along that lines said by him - would certainly save one some serious $$$.

Pat
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Old 12-22-2005, 01:05 PM   #21
flanders
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In regards to cams, research Delta Cams in the NA Forum. Apparently $75 ea. is well worth it to most people. SOunds like a good deal to me.
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Old 01-03-2006, 10:28 PM   #22
EastsideLegacy
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Hello where might i find these delta cams for my DOHC motor for 75$ each ...
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Old 01-04-2006, 12:04 PM   #23
flanders
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uh www.deltacam.com I think. Search!

Last edited by flanders; 01-04-2006 at 02:19 PM.
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Old 01-04-2006, 01:13 PM   #24
Huffer
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Quote:
Originally Posted by flanders
uh www.deltacams.com I think. Search!
You might want to check that. Maybe you should check your links before you post.
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Old 01-04-2006, 02:20 PM   #25
flanders
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You could have fixed the link in your quote. Anyway...

I have not heard anything bad about the Cams from those people.
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