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Old 07-09-2010, 12:29 AM   #26
STiGuy23
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i have cp's in mine and im just completing a full build right now. the block i pulled out with the cp's was making a noice similiar to the last video posted in here^^^^. im rebuilding it cause the check light started flashing (misfire) due to #1 being 30 psi low on compression. now the build im doing is in a different case using the stock bore with new eagle h beams and my cp's from my other block. we gave it a slight hone to clean up the cylinder walls and the piston to wall clearance is 0.0035. im going to run them a slightly bit tighter cause i dont plan on running super high temps and i dont like piston slap diesel noises lol.

now if u guys have ever installed forged pistons, they have more slap than stock cause forged pistons have a higher expansion rate than the stockers, so there must be more clearance for expansion allowance. dont quote me on this, but i believe the stock ptw clearance should be 0.002 to 0.003 while the average forged piston will say to run like ~0.005 +/- 0.001. also the forged pistons are much more tapered top to bottom than the stockers. if you slide the skirt side in the bore, ull notice that the skirt end fits much much tighter in the bore than the piston head end. being that the top of the piston sees the most heat, it will have the greatest expansion compared to any other part of the piston, hence the tapering. the teardown video above where they wobble the piston in the bore, this is actually what you hear when it is very first started cause they are cool and contracted, hence they are the loudest during a cold start. as the piston head heats up and expands to fit the bore, the ptw clearance tightens up and thus this is why the slapping noise seems to subside some. however, forged pistons will always have a slap to them being that when it is up to temp, the ptw clearance will at tightest at normal opp temp still be roughly double the factory ptw, which is what forged pistons are supposed to run at. if they were designed to expand to the factory ptw and normal opp temp, you would have major trouble if the engine were to for some reason overheat or if your tune produces higher than normal egt's, so they have some leway for above normal temps to expand a bit more without having a run in with the walls.

i realize some of you who read this will be like "well thanks for pointing out the obvious..." but for those who are still grey on the topic, i hope this helps...
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Last edited by STiGuy23; 07-09-2010 at 11:00 AM.
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Old 07-09-2010, 01:42 AM   #27
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4 and 1/2 thousanths seems like a lot especially if the pistons have a coating of 1 thousanths on them. you know the coating will wear off and the ptw clearance will be even more. What brand piston needs .0045 ptw clearance?
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Old 07-09-2010, 02:50 AM   #28
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CP manual says .0030 PTW
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Old 07-09-2010, 03:09 AM   #29
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I just had my 02 WRX engine rebuilt. It was sitting for about 6 months before I had the funds together to get this done. This is what the local mechanic did for me:
2.0 stroker motor out of a old 2.0 case (stroker is 2.0 pistons but with the 2.5 crank/rods). It is built with ACL bearings a nitrided crank and Mahle forged pistons

It just has 150 miles and it starts right up. Still has stock 02 turbo. It makes this ticking/clicking noise. One guy said something about valve clatter. This the you tube video here.


It seems to be running good, still in break in period. Some say SLAP, others say this is just normal. It makes this noise noticeably at idle no matter cold or warm engine. It seems to disappear once actually driving. Thanks for any input.

Sorry for crappy video.
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Old 07-09-2010, 10:44 AM   #30
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Quote:
Originally Posted by charliew View Post
4 and 1/2 thousanths seems like a lot especially if the pistons have a coating of 1 thousanths on them. you know the coating will wear off and the ptw clearance will be even more. What brand piston needs .0045 ptw clearance?
no there is no coating on them.... 0.0045 is as loose as it will be.

*** also i should have been more clear.... the 0.005 ptw clearance is more of a american v8 big block clearance. for the smaller import engines, most* piston manufacturers recommend running +0.001 over stock ptw....

Last edited by STiGuy23; 07-09-2010 at 11:14 AM.
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Old 07-09-2010, 10:58 AM   #31
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Quote:
Originally Posted by STiGuy23 View Post
no there is no coating on them.... 0.0045 is as loose as it will be.
*** sorry guys im retarded.... lol

i just looked back at my paper with all the specs on it and i read it wrong. the block im using had a 0.003 ptw with the cp's but it needed a hone which took off 0.0005, which brings us to 0.0035. the 0.001 piston coating made me think back about it cause my pistons dont have coatings...

^^^ sorry guys i was thinking again lol
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Old 07-09-2010, 04:53 PM   #32
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If I remember correctly some of the forged pistons use the offset pin boss to help alleviate the rock of the piston like the stock pistons.
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Old 09-19-2010, 01:42 AM   #33
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so you and i have the same problem, but it seems there was never a answere? ive been searching around and found this... i tried making a post but got barely any response

here is an a thread i did find, which sounds exactly like my problem... (1500-2000rpms) ticks loudly... everyone can hear it and im embarrsed cuase i spent so long "perfecting" my car.

http://www.iwsti.com/forums/2-5-lite...-2000-rpm.html

i think that one concluded with changing the oil....?

please help me seriously! ah

-mason
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Old 09-20-2010, 08:48 AM   #34
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So is the first video in post #3 the timing belt tensioner? Would like to know b/c this is exactly the sound my car is presently making.
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Old 03-27-2011, 01:15 PM   #35
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Question... so if it's the timing belt tensioner, will the knock go away after the engine warms up? I'd imagine not but what do I know?

I've been having knock issues on my '02 this past week but it goes away after 10 minutes or so. Oil level is fine too.
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Old 03-27-2011, 04:04 PM   #36
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i can't believe that blown tensioner didn't wreck valves...

this video...


that shows the loose piston in the cylinder pretty much summed up my concerns.
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Old 04-25-2011, 10:19 PM   #37
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Quote:
Originally Posted by Tecolote View Post
Question... so if it's the timing belt tensioner, will the knock go away after the engine warms up? I'd imagine not but what do I know?

I've been having knock issues on my '02 this past week but it goes away after 10 minutes or so. Oil level is fine too.
Anyone? The only time the engine knocks is from a cold start. I'm thinking it may be piston slap but overall I have no damn clue.
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Old 04-27-2011, 09:12 PM   #38
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Quote:
Originally Posted by TurboQueef View Post
I think you are referring to my post.. and the answer for me is: we are not replacing the pistons just using .002 thickness coating on the pistons..

I think the OP of this thread is experiencing slight piston slap from a first time build

JB
Quick update: Ron was not happy with the piston to wall clearance even with the coating on the piston skirts so... he gave me a spare block he had in the shop... he had it machined to provide a tighter fit. I have 7800 miles on the refreshed build... I can hear some piston slap but it is from all cyl's and it is much less than I had with first build!!!
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Old 04-27-2011, 09:18 PM   #39
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Quote:
Originally Posted by Tecolote View Post
Anyone? The only time the engine knocks is from a cold start. I'm thinking it may be piston slap but overall I have no damn clue.
It sounds like piston slap... but you may want to send an oil sample to Blackstone labs for a test... if you have some issue with internal engine parts it probably will show up in the test.

When my STi started making the slap... I was REAL worried... but all oil tests came back fine ... and as you could see in the tear down video, there was no problem.

Here is a link to one of my oil reports: LINK
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Old 04-28-2011, 06:08 PM   #40
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what heads are on the engine???...I have had a recent customer come in with what was thought to be piston slap on a hybrid with 2.0 heads...As we all know the 2L heads are prone to cracking,which was the case. A hairliner from valve seat to spark plug threads kept allowing the spark plug to back out. In all honestly it sounded just like piston slap. May be worth a check
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Old 04-28-2011, 10:46 PM   #41
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Quote:
Originally Posted by TurboQueef View Post
It sounds like piston slap... but you may want to send an oil sample to Blackstone labs for a test... if you have some issue with internal engine parts it probably will show up in the test.

When my STi started making the slap... I was REAL worried... but all oil tests came back fine ... and as you could see in the tear down video, there was no problem.

Here is a link to one of my oil reports: LINK
Thanks! I've pretty much confirmed the knocking isn't coming from the tensioner but from the block area. I'll have to get that oil analysis to make sure everything is running right.
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Old 12-03-2012, 05:47 AM   #42
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Quote:
Originally Posted by juanmedina View Post
I agree with Turboqueef, subaru motors are just really noise , even worse built. People always get a head of themselves. My car sounds like yours and I believe is pistons slap, I am only taking it apart until a see rod through the block

My vid is crappy I used my phone, you can hear the slap on the end of the vid

YouTube- engine
My build sounds just like that, like a little Izuzu diesel truck. Has 10k on the build. Sounds louder after i put in a 30 weight oil now in the winter. Switched back to rotella 15-40 and seems to have quiet things down a bit.
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Old 06-03-2020, 07:09 AM   #43
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Hi All, sorry to revive an old thread but I have the same noose as the 2nd video (black subaru).

On cold start I have no noise and when engine is warm the noise becomes noticeable. The timing belt etc were change only 10,000km ago (12mths).

I don't have any loss in power and oil level is fine. Should i be concern?

Noise coming from LH side, engine is a EJ255 for the 2012 WRX G3.

Quote:
Originally Posted by mtcs View Post
It never does it in neutral. Only when going through 1st-2nd gear with very light throttle. The car has tons of oil. It has never run out of oil yet in it's short (1 month) life. Always running Rotella T 15-40.

So it might be the timing belt tensioner.
It is over 7 years old afterall

YouTube - Subaru STi rod knock, piston slap, spun bearing, belt tensioner
and even worse...(broken)
YouTube - Dead timing belt tensioner. Impreza WRX

Going to replace the tensioner and see where that gets me.
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