birz

It has to be 0.006 (in my case it was 0.0055 cause it's more a street car than a race car) ,, when you compare to wiseco or JE they're in the range of .003 or so ,, why so much difference???

99B16Si

different applications will require different piston to wall clearance. u need to look at how much power u expect to make out of the motor. obviously the more power u make the more heat that is created in return. more heat means more expansion. id say the least amount of piston to wall youll want for a 300whp car would be about .003 and for a higher boost application id say .006 is the max. .005 has always worked well for me. just mkae sure your not too tight because if you are oil will not be able to get in between the skirt of the piston and the wall and you will scortch the piston and probably sctrach the cylinder wall

birz

the thing is it has already been installed, and my mechanics called Ross because he found it was a pretty big clearance, and he then asked for a street application and the guy at Ross answered him to put 0.0055 of clearance,, so my engine is built now,,,,, I can't do much thing about it ,,,, do you think it will wear more quickly??? My car is currently at 220-250HP, next year I plan on 300-350

99B16Si

youll be fine with that much clearance. just might be a little noisy on cold starts till the pistons warm up

birz

thanks for the answers,, I drove 516KM since the rebuilt,, and I must admit that when I start up the engine it is quite noisy, but hey! those are forged internals afterall


even when the engine is warmed up (180-200 degree) it is still noisy at partial throttle, but idle is almost like stock.

birz

maybe Ross pistons require more clearance than JE, Wiseco, etc.. !?!

99B16Si

i doubt it. most forged pistons use about the same amount of silicone, excpet srp's off the top of my head. listen to the motor after u get on it, i bet theres no noise

Finest

^ What he said. Might experience some piston slap on cold start ups, but once it's warmed up, it should be fine.

I bet the Ross pistons have a slightly different silicone content, which explains the extra clearances.

birz

but is it normal that under part throtle I hear the pistons?? even when the motor is warmed up? is it because it's still in the breakin phase????

99B16Si

honestly, no its not normal for a daily driven car that making under 250whp.

now will it hurt anything?? probably not for a while, over time the cylinder walls may get scratched and the sides of the pistons may get a little scuffed. but as long as your ring gap was done correctly the motor should be fine for quite a while

earl

I think someone gave you some bad advice. No piston manufacturer would specify clearance that they know would give you slap.
.0055 seems like way to much..as others have said.

birz

but look by yourself here:

http://www.rosspistons.com/pdf...n.pdf

it says .006 for turbo engines small bore.

earl

Yeah, it says .006 for turbo engines. Seems pretty large to me

Bailhatch

How do SRP clearances compare to other lower silicon pistons and stock cast pistons?

tony1

We ran .006 on kenny's motors too. It will have noise, but it's ok. Ross knows what they want their clearances at. You WILL have noise under light acceleration, don't worry about it.

lazerus

sounds like a set of pistons that you shouldn't use in a street motor!

kpt4321

I'm with Laz. Whether or not that's the right spec, you don't want a piston with slap in a street car.

birz

you can look on the webpage of ross and they say that their pistons are for both street and race.

All Honda kits include special heavy-duty pistons, which are designed and manufactured to perform flawlessly under the extreme heat and PRESSURE associated with turbocharged engines. Ideal for both street and serious competition , these pistons are loaded with extra features such as annular pin hole grooves with double forced oil holes to prevent pinhole galling, and taper lands to prevent scuffing. Extra thick lands for superior ring groove support under extreme pressure are made possible by intersecting the ring groove with the pinhole and using ROSS Oil Ring Support Rails. 4340 taper bore, hard-chromed extra heavy duty pins, along with Ross Racing Rings are also included. Pin information can be found here. , and ring information can be found here. .


so who is right????? is my engine going to last only 1000K or what???

birz

anyone?

IloveNewt

Just to clear something up....sorry if you feel im jackin your thread but...
lower silicone content = more expansion but also more strength which leads to bigger piston:wall clearence which leads to more slap correct?

Where as higher silicone content = less expansion but less overall strength of the piston so you can run tighter clearences and less slap?

30psi Teg

I run roos in my car and they told me at Ross to run about .005 and .006 is the max so I would say your fine might just be a little noisy

earl

I could be wrong, won't be the first time, but I just feel that noise cannot be good for a motor. It has to be the result of two pieces of metal knocking together. How long can they continue to knock together before clearance changes or parts fatigue and fail. Could .006" clearance be a bandaid for a poor design? Most piston forging come from the same few foundries and are of the same material. Why does one piston need only .003" and another needs .006"?

boosted hybrid

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">I could be wrong, won't be the first time, but I just feel that noise cannot be good for a motor. It has to be the result of two pieces of metal knocking together. How long can they continue to knock together before clearance changes or parts fatigue and fail. Could .006" clearance be a bandaid for a poor design? Most piston forging come from the same few foundries and are of the same material. Why does one piston need only .003" and another needs .006"?</TD></TR></TABLE>

I have to agree with Earl. Most of the pistons on the market are set at a 0.003 piston to wall clearance, with the exception of endyn/wiseco's set at 0.0022". Doubling the clearance spec of 0.003" to 0.006" would enhance wear rate on the cylinder walls from the piston slap. On a race engine where 1000-2000 miles of use before tear down a looser tolerance can be used since the extremes of boost, cylinder pressure and temperature are going to occur. On a street engine with too loose of a clearance increased wear is going to occur, and rebuild will have to be sooner. I was nervous to run my piston to wall clearance an extra 0.0001" from the 0.003" CP recommend to give some extra expansion at the boost levels I will be running the engine. Audible piston slap on a warmed up street driven engine is something you want to avoid.

birz

anyway, it's kind of too late isn't it?

so I'll let you guys know if they hold the road

kpt4321

I agree boosted, that's what I was hinting at. The poor guy is going to end up with cylinders that are an oval shape.