.dave

I'm currently running SRP pistons in a D16Y8, stock sleeves slightly overbored. Ever since my engine was built, it has always been loud at idle (mechanical noise-wise). I've adjusted the valve lash multiple times and each time has done nothing to quiet it down. I'm beginning to think that the engine builder who bored/honed my block may have gone a little too loose on the piston-to-wall clearance.

Anyways, it makes the typical piston slap noise that I guess is fairly common on engines with forged internals, however the noise does not quiet down at all after the engine has warmed up. Also, if I make a hard pull with the car, it will smoke for a bit at idle out the exhaust, not pouring smoke out the back, but just enough to notice it looking in the mirror.

Has anyone had a similar experience before, any similar symptoms? If not, any ideas on what might be going on?

turtle-eg

I used to run SRP pistons with stock overbored sleeves also, it slapped at idle but quiet down off idle. It's also a little louder when cold.

.dave

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turtle-eg &raquo;</TD></TR><TR><TD CLASS="quote">I used to run SRP pistons with stock overbored sleeves also, it slapped at idle but quiet down off idle. It's also a little louder when cold.</TD></TR></TABLE>

Thats what I've heard from a lot of people, but mine seems to be just as loud whether its warm or cold.

ELSpool

I had an SRP Y8 block as well, mine was loud too. 3 years later and 3 owners later, it's still taking the beats like a champ. I think it's the piston, everyone said they should be quiter with the higher sil%, but my CP's are half as loud in my new block. There are 2 others in my city who hav ethe same pistons, all have that diesel sound to them.

Flr Power

CP recommends 0.0035 piston to wall clearance but it's too much in my opinion. You only need that big clearance if you race the engine by doing 1/4 mile runs while the engine is cold to prevent engine seizing.

I have measured stock pistons and my CP by putting them in an oven at 400 F for 30 minutes and the resulting expansion was no more than 0.0002 between the 2.

I am currently running 0.0025 clearance but my next built will be at 0.002 max.

RacerXI

My CP piston motor rivaled a diesel when cold, but was fine once it warmed up. It was noisier than a stocker, but not by much.

lightcrx

my older arias pistons required .005 talk about a diesel, its loud at startup but as it warms up it queits down but it still loud


Modified by lightcrx at 9:09 AM 11/3/2006

jjspec

Stock (cast) pistons require less piston to wall clearance than forged parts, mainly due to expansion rates being different. Factory clearances are .002 - .004. You need to go with the piston manu suggestion of at least .0035 or you risk some piston to wall scuffing. Too close and it will eat itself up.

Dac

CP's and Wiseco's are notorious for piston slap. Arias are much more quiet.

Flr Power

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jjspec &raquo;</TD></TR><TR><TD CLASS="quote">Stock (cast) pistons require less piston to wall clearance than forged parts, mainly due to expansion rates being different. Factory clearances are .002 - .004. You need to go with the piston manu suggestion of at least .0035 or you risk some piston to wall scuffing. Too close and it will eat itself up.</TD></TR></TABLE>

Factory clearances is around 0.001. The expansion rate I calculated by putting a cast pistons and my CP pistons in a heated oven for 5 minutes were nearly identical.

.dave

The thing is, I'm not exactly sure what the block was bored to, and can't really go back to the engine builder to find out since the guy is a dickbag and I'm through dealing with him.

The sound doesn't bother me at all, its the light smoking at idle after a hard pull that does. I'm going to do a compression test/leakdown over Thanksgiving break I think.

preyluda

"Stock (cast) pistons require less piston to wall clearance than forged parts, mainly due to expansion rates being different. Factory clearances are .002 - .004. You need to go with the piston manu suggestion of at least .0035 or you risk some piston to wall scuffing. Too close and it will eat itself up."


Like you know
Go hop back in your 18 second civic with your electric supercharger and spoon chip.

EK FLY

back in the days when I try to put my motor together I slap 81mm pistons into a 81.5 block , lol smoked like crzy and slap i could hear it a mile away but I didnt measure the pistons so I tought they were 81.5 too

Muckman

iTrader: (2)

Ive rebuilt my block 3 times and used CP pistons everytime, Never had abnormal piston slap.

Dave, the only way to really fix the problem without boring and moving up a size is to pull the pistons and send em over to swaintech. Have them apply a thick layer of their poly moly coating on the skirts. Its only $14 a piston, it will fill up some of the excess piston-to-wall clearance and give you some additional lubrication protection.

.dave

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">Ive rebuilt my block 3 times and used CP pistons everytime, Never had abnormal piston slap.

Dave, the only way to really fix the problem without boring and moving up a size is to pull the pistons and send em over to swaintech. Have them apply a thick layer of their poly moly coating on the skirts. Its only $14 a piston, it will fill up some of the excess piston-to-wall clearance and give you some additional lubrication protection.</TD></TR></TABLE>

I'm going to do a compression test/leakdown in a few weeks and then pull the head and check the cylinder walls out. Hopefully they're not scored too badly.

theEGkid

i run 8.5:1 Compression pistons in my ls vtec setup.; I have The good ole desiel sound with a lil bit of smoke here and there. Not sure if its from the turbo or motor,but ive had no promlems with the motor. Runs like a champ 15 psi daily driven. i worried about it every damn day and people just say its normal with SRP Pistons

yellowturbo

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Flr Power &raquo;</TD></TR><TR><TD CLASS="quote">CP recommends 0.0035 piston to wall clearance but it's too much in my opinion. You only need that big clearance if you race the engine by doing 1/4 mile runs while the engine is cold to prevent engine seizing.

I have measured stock pistons and my CP by putting them in an oven at 400 F for 30 minutes and the resulting expansion was no more than 0.0002 between the 2.

I am currently running 0.0025 clearance but my next built will be at 0.002 max.
</TD></TR></TABLE>

Who told you that your pistons are at 400F in your engine lol I think that the temperature are way higher than this in your engine... so be careful when testing your pistons in your oven

I Have an STD

still havent taken it apart dave?

i've heard dave's motor firsthand, and let me tell you, its LOUD. i've heard ALOT of built motors, but i will say, dave's is the loudest.

i bet the builder didnt read ANYTHING off the spec sheet for your pistons dave, he probably just bored it out to much and it a little slappy. i say run it till it blows

.dave

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by I Have an STD &raquo;</TD></TR><TR><TD CLASS="quote">still havent taken it apart dave?

i've heard dave's motor firsthand, and let me tell you, its LOUD. i've heard ALOT of built motors, but i will say, dave's is the loudest.

i bet the builder didnt read ANYTHING off the spec sheet for your pistons dave, he probably just bored it out to much and it a little slappy. i say run it till it blows</TD></TR></TABLE>

No, I haven't taken it apart yet. I'm coming up on finals week for this quarter so I haven't had time to do anything the past few weeks.

Everyone I've talked to has noticed how loud it was, and its definitely coming from the block, not the head. I'll see what the situation is when I do a compression test and pull it apart.