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Old 01-22-2006, 10:50 PM   #1
Lachlan
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Default Piston slap?

Did all phase 1 engines have piston slap or is that just a usdm thing?
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Old 01-22-2006, 11:39 PM   #2
HndaTch627
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subaru motors tend to be prone to piston slap due to its design however the phase 1 EJ25 suffered heavily from it due to the large bore and stroke of the piston
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Old 01-22-2006, 11:58 PM   #3
Lachlan
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I was wondering because when I start up my ej20k if it's cold I hear some knocking noise from the engine, but it goes away when it gets warmer.
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Old 01-23-2006, 01:11 AM   #4
Hurley 2.5 WRS
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yeah, thats cause the forged pistons expand more, so they have a larger tolerence when cold. common thing for forged pistons.

edit, 11:11.......

Last edited by Hurley 2.5 WRS; 01-23-2006 at 01:22 AM.
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Old 01-23-2006, 01:14 AM   #5
Lachlan
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good to know, thanks. I did read somewhere on this board that forged pistons expand less, but I guess you can't trust everything you read here...

Related but ot: Did the JDM EJ20's pistons have skirts or no?
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Old 01-23-2006, 01:22 AM   #6
Hurley 2.5 WRS
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yessir
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Old 01-23-2006, 04:46 AM   #7
HndaTch627
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Quote:
Originally Posted by Lachlan
good to know, thanks. I did read somewhere on this board that forged pistons expand less, but I guess you can't trust everything you read here...

Related but ot: Did the JDM EJ20's pistons have skirts or no?
forged pistons do expand less but they are still alumnium which means they are going to expand. Forged pistons usually are built with tighter clearances because of the fact that they won't swell like regular cast alumnium pistons. Sounds to me like you have normal piston slap, even my USDM wrx swap has a little bit on the very very cold mornings.
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Old 01-23-2006, 11:27 AM   #8
Matt Monson
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Quote:
Originally Posted by Lachlan
good to know, thanks. I did read somewhere on this board that forged pistons expand less, but I guess you can't trust everything you read here...

Related but ot: Did the JDM EJ20's pistons have skirts or no?
I have both forged and non-forged Ej20G pistons. I will see if I can find my pictures...
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Old 01-23-2006, 11:29 AM   #9
Matt Monson
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Forged EJ20G piston...
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Old 01-24-2006, 02:36 AM   #10
2slofouru
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Default not a turbo ej but

My ej25 phase 1 does that too, in the morning. I worry about it being a bearing or excessive piston slap, I hope it doesn't develop into anything soon. It does go away by the time the engine warms up though.
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Old 01-24-2006, 11:10 AM   #11
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Quote:
Originally Posted by HndaTch627
forged pistons do expand MORE but they are still alumnium which means they are going to expand. Forged pistons usually are built with MORE clearance because of the fact that they will expand more than regular cast alumnium pistons. Sounds to me like you have normal piston slap, even my USDM wrx swap has a little bit on the very very cold mornings.

Fixed that for you.

Factory EJ clearances: <.001"

CP/JE/Ross/Wiseco 2618 forged piston-bore clearance: ~.0035 to .0055" depending on application.
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Old 01-24-2006, 02:04 PM   #12
HndaTch627
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Quote:
Originally Posted by n2xlr8n
Fixed that for you.

Factory EJ clearances: <.001"

CP/JE/Ross/Wiseco 2618 forged piston-bore clearance: ~.0035 to .0055" depending on application.
ah crap...you are right, i said that backwards
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Old 01-24-2006, 02:16 PM   #13
n2xlr8n
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Quote:
Originally Posted by HndaTch627
ah crap...you are right, i said that backwards
I knew that you knew....that's why I didn't say "get your facts straight, you stinkin bastich"

S.
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