Forge pistons...noisier
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From: NY, USA
Forge pistons...noisier
Ok, i readjusted my valves and still at low idle I hear a knocking noise, not terribly loud and it seems to be coming from high in the block by putting a stethoscope (long socket extension) on the engine. Its the same whether the car is hot or cold.
It is not noticeable as i up the rpms even just past 1000 and at high rpms engine is smooth and no real noise,
is this the forged pistons i am hearing at the very low rpms?
do i worry?
It is not noticeable as i up the rpms even just past 1000 and at high rpms engine is smooth and no real noise,
is this the forged pistons i am hearing at the very low rpms?
do i worry?
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From: LA, CA
Re: Forge pistons...noisier (sgT)
Jeeeez... I just dropped in my 9:1 SRP D16Y8 engine into my car during the past week... christ does it make a lot of diesel-y sounds! Piston slap like a **** until operating temp, at which point the slap mellows out and sounds like a B-series engine in need of a valve adjustment.
But to answer your initial question yeah. Piston slap.
But to answer your initial question yeah. Piston slap.
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From: Northern, VA
Re: Forge pistons...noisier (GruvyTune)
Yup.. forged pistons are definetly noisier.. My motor has 10k miles on it.. and sometimes I swear the noise is louder at times, but it's just my mind playing tricks on me.. If you're a paranoid person it can drive you crazy.. 
-Mike
-Mike
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Re: Forge pistons...noisier (blkDOHCsol)
hey i have SRP 9:1 pistons too and i hear it. damn it's hella loud when revving from 1k rpm to 2.5k rpm! sounds kinda like a damn diesel motor! i have been wondering what the noise was for the longest time! thank God i'm not the only one who has this problem! i thought i built my motor wrong or something!! *wipes away sweat* anyone know a cure for this problem though?? or will it ever go away? the sound is making me sick and embarrassed to drive my car around... 
[Modified by shermanyang, 3:56 AM 8/27/2002]
[Modified by shermanyang, 3:56 AM 8/27/2002]
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From: Northern, VA
Re: Forge pistons...noisier (shermanyang)
Yeah, I have 9:1 wisecos and only at around idle can u hear them. Thing is.. w/ the hood open you can't hear it very clearly because of the noise from the rest of the engine.. but when sitting in the car w/ the radio off it's definetly audible. It's like a tapping/knocking sound. It shouldn't be THAT loud..? Either way.. it is normal..
-Mike
-Mike
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From: North tonawanda, New York, United States
Re: Forge pistons...noisier (GruvyTune)
with forged pistons you have to run a larger piston to bore clearance to allow for the "growth" as they go thru the heat cycle. Altough i haven't really ever had problems with this i tend to run my clearances as tight as possible, obviously allowing for the norm. So at cold operating temps it isn't uncommon to expierience piston slap. If it was a piston pin it would be like a valve train noise and wouldn't go away with accel. YOu can have the pistons coated on the thrust side with acoalite coting and this will resist the piston slap and scuffing on the thrust side of the cylinder wall
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Re: Forge pistons...noisier (earl)
they are pins with locking rings at the end. they fit with little clearance. just enough to spin a little. i guess that is another posibility. i really can't even hear it once i'm on the throttle a bit and i redline the engine without any hint of the noise or excessive vibration. only thing i have is the same old resonance at 1500rpm where my engine vibrates a little and my timing belt shudders a bit then goes away at higher rpms. it did that even before the rebuild!
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From: NY, USA
Re: Forge pistons...noisier (shermanyang)
hey i have SRP 9:1 pistons too and i hear it. damn it's hella loud when revving from 1k rpm to 2.5k rpm! sounds kinda like a damn diesel motor! i have been wondering what the noise was for the longest time! thank God i'm not the only one who has this problem! i thought i built my motor wrong or something!! *wipes away sweat* anyone know a cure for this problem though?? or will it ever go away? the sound is making me sick and embarrassed to drive my car around...
damn,,mine's not that loud! mines just a mild ticking sound a little deeper tone than valves or injectors which is more like a clicking.
[Modified by shermanyang, 3:56 AM 8/27/2002]
damn,,mine's not that loud! mines just a mild ticking sound a little deeper tone than valves or injectors which is more like a clicking.
[Modified by shermanyang, 3:56 AM 8/27/2002]
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Re: Forge pistons...noisier (earl)
How was your pin fit? They can give you a noise similar to valve train. Will not change hot to cold.
[Modified by earl, 7:45 PM 8/26/2002]
[Modified by earl, 7:45 PM 8/26/2002]
Greg
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From: Irvine, CA, usa
Re: Forge pistons...noisier (GruvyTune)
Gruvy..Did you balance your crank? Stock harmonic balancer or aftermarket? Flywheel balance? Timing belt shudder at 1500 before and after rebuild may be your clue. Sounds like pins are ok. Look for the same part used before and after.
[Modified by earl, 9:09 AM 8/27/2002]
[Modified by earl, 9:10 AM 8/27/2002]
[Modified by earl, 9:09 AM 8/27/2002]
[Modified by earl, 9:10 AM 8/27/2002]
MiG-21 superfan
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From: near the ocean, Moderator City, NJ
Re: Forge pistons...noisier (GruvyTune)
Forged pistons can be hella loud when cold dude to thermal expansion differences from cast. THey take longer to heat up and slap around in their bore for a while. just like 91f22 said. Forged pistons however, at revs, should be relatively quiet. At idle they might make your engine sound like a lil' diesel, but while driving you definately should not notice to the point where your questioning the build...but, in regards to GruvyTune, your case sounds normal.
[Modified by builthatch, 1:52 PM 8/27/2002]
[Modified by builthatch, 1:52 PM 8/27/2002]
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From: NY, USA
Re: Forge pistons...noisier (earl)
did not balance the crank only polished, and flywheel was resurfaced a yr ago when i put in a new clutch.
i'm using the stock crank pulley and removed the unorthodox one i had on there for just that fear.
once i get above 1500rpm there is no vibration in the engine seems to be a mode just at that point only.
i'm using the stock crank pulley and removed the unorthodox one i had on there for just that fear.
once i get above 1500rpm there is no vibration in the engine seems to be a mode just at that point only.
MiG-21 superfan
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From: near the ocean, Moderator City, NJ
Re: Forge pistons...noisier (GruvyTune)
Balancing is something I always do, no matter what, balance everything, or atleast check, anyway, enuff of my preaching- in regards to the noise, I think you build is probably fine. Your case sounds normal.
[Modified by builthatch, 1:54 PM 8/27/2002]
[Modified by builthatch, 1:54 PM 8/27/2002]
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From: Irvine, CA, usa
Re: Forge pistons...noisier (GruvyTune)
I'm not sure of the source of your noise but for longer life of the engine, I would consider a balance of the crank only (not pistons and rods, etc) and also a balance of the flywheel. That should fix the 1500 rpm shutter that may be caused by the dynamics of a slight out of balance condition. (The out of balance could be the source of the noise.) Also check oil pressure at idle. Should be about 30 lbs.
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From: Northern, VA
Re: Forge pistons...noisier (earl)
30 lbs... That high? I've never seen 30 psi at idle even before I put the turbo on. Before the turbo I was sitting at about 25 psi at idle, now it sits around ~18.. I'm guessing the "oil leak" caused by the turbo and the increased flow causes a pressure drop..
On a similar note.. how much do you have to shim the pump to raise the pressure another 5 lbs or so? Thanks.
-Mike
On a similar note.. how much do you have to shim the pump to raise the pressure another 5 lbs or so? Thanks.
-Mike
Re: Forge pistons...noisier (SlowTeg)
man i love this site...but to get to the point, i just checked my motor again today. while revving with the car not in gear, there is no slapping/knocking noise. but when i put the badboy in gear and start to roll, that's when the noise starts to kick in. it does however go away after 3k rpm. is piston slap a bad thing? if it is, i'm gonna have to take my pistons out soon and buy new ones. that always sucks ****!
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Re: Forge pistons...noisier (earl)
is that 30lbs measuring at the stock oil sensor pickup location? I have my oil pressure gauge at the turbo inlet so I am sure the pressure before the -3an feed line must be higher.
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From: Irvine, CA, usa
Re: Forge pistons...noisier (GruvyTune)
I see 25 lbs as an acceptable minimum measured from the stock location. Never shim a pump more than .050 and only as a last resort.
BTW, I once had a customer show me his gsr motor with 5 lbs at idle. I pulled his oil pan, pounded out the dented bottom, opened up the crushed pick up opening and put the pan back on. Pressure jumped to 25 lbs.
BTW, I once had a customer show me his gsr motor with 5 lbs at idle. I pulled his oil pan, pounded out the dented bottom, opened up the crushed pick up opening and put the pan back on. Pressure jumped to 25 lbs.
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From: Sydney, Australia
Re: Forge pistons...noisier (shermanyang)
man i love this site...but to get to the point, i just checked my motor again today. while revving with the car not in gear, there is no slapping/knocking noise. but when i put the badboy in gear and start to roll, that's when the noise starts to kick in.
'cause it's under load???
it does however go away after 3k rpm. is piston slap a bad thing?
from the above posts - it doenst seem to be bad...just part of forged life.
if it is, i'm gonna have to take my pistons out soon and buy new ones. that always sucks ****!
'cause it's under load???
it does however go away after 3k rpm. is piston slap a bad thing?
from the above posts - it doenst seem to be bad...just part of forged life.
if it is, i'm gonna have to take my pistons out soon and buy new ones. that always sucks ****!
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From: Irvine, CA, usa
Re: Forge pistons...noisier (tinkerbell)
Remember, pistons are not supposed to slap and it's not normal. Even if everyone u know has piston slap, it's still not normal and will lead to piston failure.
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