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Phase I block, Phase II pistons and heads, 2.5?s


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11 replies to this topic

#1 Gloyale

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Posted 03 August 2010 - 11:22 AM

Backstory:

We've been planning to put a Phase II SOHC 2.5 in my bro's lifted Legacy for a while now. Finally got around to doing it. Put her in and the engine was knocking like the hammers of Thor. great, engine we bought is a pile of garbage. And the crank is toast, and the other crank we have is toast.

O.K. so we buy a good Phase I DOHC engine with bent valves.

Go to swap over heads, and looking at where the valve notches are on the different pistons it looks like the DOHC pistons will hit the SOHC vavles.

So we swap the SOHC pistons into the block. They don't rise as far out of the cylinder...hmm...well we will see how it goes.


So we done it now. Phase I block, Phase II pistons and Heads. Phase II intake with orignal to car EJ22 throttle body, coil, and harness mounted to it.

Not sure how it will run once we fire it up.

Got the heads on and putting it in the car today.

I just thought I'd let ya'll make some predictions today and I'll report after it's in and running.

Edited by Gloyale, 03 August 2010 - 11:24 AM.


#2 renob123

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Posted 03 August 2010 - 11:44 AM

I must be missing something. What was your reasoning behind this setup rather than the Frankenmotor?

Jacob

#3 grossgary

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Posted 03 August 2010 - 08:01 PM

great job beast.

silly questions - could you have just left it? if it retains timing seems like it would be okay, some engines are piston to valve interference right?

can you swap valves? that seems like an obvious "no", but just asking.

#4 Gloyale

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Posted 03 August 2010 - 10:34 PM

I must be missing something. What was your reasoning behind this setup rather than the Frankenmotor?

Jacob


Lack of available cost effective Phase II bottom end solution.

I have in my shop, two good Phase II blocks, 5 usable rods, and ZERO good cranks (i have 3 cranks but all have bad rod bearing problems costing $ to fix)

The Phase I block w/ low miles and a good bottom end presented itself as a cheaper and easier solution than a $300+ dollar crank, bearings, and rings.

Re: Phase I block, Phase II pistons and heads, 2.5?s
great job beast.

silly questions - could you have just left it? if it retains timing seems like it would be okay, some engines are piston to valve interference right?

can you swap valves? that seems like an obvious "no", but just asking.


We had already made our adapted phase II manifold (soldered injector connectors from forrester onto legacy harness, phase I legacy throttle body/w adapter plate)

And also we really wanted to use the SOHC heads for offroad reliability. the SOHC can slip a few teeth and not bend valves.....slighlty less vulnerable.

Also, the DOHC pistons come out of the block at the top of there stroke, SOHC heads use a thin gasket, and it seemed risky.

SOHC pistons on the phase I block come up just to the deck face, and have notches that match the heads.

Valves are at a different angle, and different sizes. As well, the SOHC valves are further to the edge of the combustion chamber. It really seemed like they would hit the valves even if in time.

#5 grossgary

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Posted 04 August 2010 - 06:32 AM

L It really seemed like they would hit the valves even if in time.

oh wow. i figured swapping valves would never work being all different geometry.

#6 Gloyale

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Posted 04 August 2010 - 10:27 PM

So it runs GREAT.......tons of torque, seems quick even for a lifted rig with big tires. No idle Air valve so it takes a bit of manual warm up, but runs great after that.

So once again, Subaru=LEGO:grin:

#7 grossgary

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Posted 11 March 2011 - 10:27 AM

Crack, i was going to do this same swap for the exact same reasons to help someone out.

I guess you can't comment on if a thicker gasket would remedy this issue? Cometic makes different thickness gaskets, wonder if they know the answer?

I doubt I'll crack the block, seems time consuming. Did you crack the block to swap pistons or no?

What all did you do - did you re-ring it, hone it, or just swap and go?

Edited by grossgary, 11 March 2011 - 10:49 AM.


#8 WJM

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Posted 11 March 2011 - 11:55 AM

No need to split the block for pistons.

11044AA610 gaskets and it'll work like I said in your other thread.

SOHC and DOHC valves on EJ25 engines are different length so they dont interchange.

#9 Numbchux

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Posted 11 March 2011 - 08:45 PM

As a matter of fact, the pistons pretty much have to come out before the case is split, so yea, they can be swapped.

That's what we've done for both motors in our rally car. stock EJ257 bottom end, drop in aftermarket pistons to raise the compression, done. Doesn't even take very long.



And yea....legos......awesome. It's pretty amazing how interchangeable these parts really are.

#10 grossgary

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Posted 12 March 2011 - 02:15 PM

As a matter of fact, the pistons pretty much have to come out before the case is split, so yea, they can be swapped

right on! smack, duh, i just split an EJ25 block a couple months ago!

when swapping pistons do you have to hone, new rings, etc or can you swap pistons from one block to another with the existing rings in place and call it good?

probably just going with the thicker gasket but still curious about piston swapping for future reference.

#11 WJM

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Posted 12 March 2011 - 03:39 PM

Take it from my loss: you absolutely NEED to do a hone and new rings.

The hone can be a quick 3-stone or such just to get the surface prepped for new rings.

I few times I got away w/out hone and/or rings but several times it has come back to bite me hard.

#12 Numbchux

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Posted 12 March 2011 - 07:11 PM

Yea...."need"? maybe not. but it's a good idea.


New rings really need a fresh hone to break in properly. I've gotten away with used rings and no hone (a friend of mine is currently running used pistons/rings in an EJ205, has been for a year and a half, without issues).


Our rally car build is using a brand-new OEM EJ257, so we didn't re-hone it for the new pistons.


I've never done a hone on an assembled shortblock though. I'd be worried about metal shavings in the bearings. I suppose a good wash would be alright.




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