Cp pistons noisey at idle ?

[Dan1200sss]

Iv been wondering if at Idle it's ok to hear a little noise from the middle/lower part of the new built motor? Cp pistons, spool rods , acl race bearings etc. It's only done 160miles so far on run I'n oil. Noise seems to go away when not idling. Doesnt sound like a bearing going to me but I'm not expert. Just wondering if I should be concerned or are Cp pistons known to do this? There .5 oversized.

[sjbsuperman1425]

it was my understanding that the CP Pistons are noisy when "cold"

[Dan1200sss]

Hmm me to... How about seeing it's got sae30 run In oil maybe it's the s*** oil getting hot and not doing it's job and alowing such a noise?

[D_Stirls]

What was the piston to bore clearance?
Also what did you get the mains and big end clearances machined to? The reason i ask is that with most big RPM and or power application your set your main and big end clearances larger than factory. i.e my mains are 0.0022 and the factory specs are 0.0008 > 0.0019. If you have gone bigger clearances i would suggest going thicker with your oil.

No noise when not idling could be related to oil pressure, are you sure it isn't your lifters that aren't making the noise, have you tried the long screwdriver on the ear trick and tried to locate exactally where the noise is coming from?

[float_6969]

CP pistons are noisy when cold. Simple fact. Call them and ask them if you'd like, but I already have. They told me that the reason is that they decided to use a material that would resist damage from detonation and make for a stronger piston at the sacrifice of noise when cold. The noise comes from the fact that the material they chose has a higher rate of thermal expansion than the stock piston. This means that given a 1° change in temperature, their piston expands and contracts MORE than what the stock piston does. This means that when the engine is cold, the pison-to-bore clearance is too great, and the pistons makes noise. Once the piston and engine block warm up, the clearances are what they should be and everything is fine. This is why the engine and piston should be heated up when measuring the piston-to-bore clearance.

I can tell you from 1st hand experience that it works. When I first built my motor, I tried to run it on 91 octane. I didn't know at the time that the compression of my pistons was over 10:1. I thought it was 9.5:1. I got A LOT of detonation. I pulled the head later to replace the HG (I thought it was leaking oil externally, but it wasn't) and found that the quench pad on the #3 cylinder looked like someone had taken an ice pick to it. This was from the detonation. To my amazement, the piston looked fine. No signs of detonation at all.

[ILOVESILVIA(S13)]

Like everyone else said, when they are cold they are a bit noisy. Does not bother me though.

[s13drifter88]

Move to a heavier oil, 10w40 should be fine. The thicker oil may potentially buffer some of the noise you hear by providing sort of a cushion and reduce some of the noise. Did you replace your oil pump when you rebuilt it???

[blownhemi]

My only worry with the high thermal expansion ratio material is, don't they have a limited window of useful temperature? As power goes up, combustion temperatures go up as well, can a piston expand up to the point where it can seize? Probably not at 15 psi, but what about big power, say 30 psi, running on E85?

[float_6969]

No, because that heat will simply be transferred to the cooling system and the temps will remain the same. Now if the cooling system isn't up to par and the motor overheats, that could seize the piston.

[r34 gtr]

Hemi, people make ridiculous power on CP pistons. I dont think there is anything to worry about.

[s13drifter88]

if your tune is sh*t or you exceed your fuel system and start leaning out then your combustion temps will begin to rise. you would prob start detonating tho long before you seize it.

[Dan1200sss]

Have listened to my mates forged ca idling just lastnight and his has the same noise as mine and he said it allways has, he's done around 25thousand kms of spirited driving on it so I guess I have nothing to worry about. My oil is curently elf running In oil (sae 30). She runs mint and burns amazingly clean and not to rich or anything. I plan to run 20-25psi when it's run In and tuned for it.

[blownhemi]

Thanks for the info, I'm relieved.
So I guess I should be okay with an AFR gauge, and the 3" radiator I've planned.

[Dan1200sss]

Is 30psi at idle good oil pressure ?

[s13drifter88]

yeah thats fine, mine only ran about 20 when i got it.

[float_6969]

If that's your hot idle oil pressure, that's really good. Mine's low and it makes the lifters noisy.

[s13drifter88]

yeah mine was about 2 min after the needle showed full op temp